Fix Configuration Binding with Instantiated Objects

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

@@ -315,12 +315,15 @@ private static void BindInstance(
  }
 
  // for sets and read-only set interfaces, we clone what's there into a new collection, if we can
- if (TypeIsASetInterface(type) && !bindingPoint.IsReadOnly)
+ if (TypeIsASetInterface(type))
  {
- object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
- if (newValue != null)
+ if (!bindingPoint.IsReadOnly || bindingPoint.Value is not null)
  {
- bindingPoint.SetValue(newValue);
+ object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
+ if (!bindingPoint.IsReadOnly && newValue != null)
+ {
+ bindingPoint.SetValue(newValue);
+ }
  }
 
  return;
@@ -530,33 +533,41 @@ private static bool CanBindToTheseConstructorParameters(ParameterInfo[] construc
  return null;
  }
 
- Type genericType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
- Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
- PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
- PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
-
- object dictionary = Activator.CreateInstance(genericType)!;
-
- var orig = source as IEnumerable;
- object?[] arguments = new object?[2];
-
- if (orig != null)
+ // addMethod can only be null if dictionaryType is IReadOnlyDictionary<TKey, TValue> rather than IDictionary<TKey, TValue>.
+ MethodInfo? addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in orig)
+ dictionaryType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
+ var dictionary = Activator.CreateInstance(dictionaryType);
+ addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+
+ var orig = source as IEnumerable;
+ if (orig is not null)
  {
- object? k = keyMethod.GetMethod!.Invoke(item, null);
- object? v = valueMethod.GetMethod!.Invoke(item, null);
- arguments[0] = k;
- arguments[1] = v;
- addMethod.Invoke(dictionary, arguments);
+ Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
+ PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
+ PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
+ object?[] arguments = new object?[2];
+
+ foreach (object? item in orig)
+ {
+ object? k = keyMethod.GetMethod!.Invoke(item, null);
+ object? v = valueMethod.GetMethod!.Invoke(item, null);
+ arguments[0] = k;
+ arguments[1] = v;
+ addMethod!.Invoke(dictionary, arguments);
+ }
  }
+
+ source = dictionary;
  }
 
- BindDictionary(dictionary, genericType, config, options);
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
+ BindDictionary(source, dictionaryType, config, options);
 
- return dictionary;
+ return source;
  }
 
  // Binds and potentially overwrites a dictionary object.
@@ -737,32 +748,38 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  Type elementType = type.GetGenericArguments()[0];
 
-Type keyType = type.GenericTypeArguments[0];
+bool keyTypeIsEnum = elementType.IsEnum;
 
- bool keyTypeIsEnum = keyType.IsEnum;
-
- if (keyType != typeof(string) && !keyTypeIsEnum)
+ if (elementType != typeof(string) && !keyTypeIsEnum)
  {
  // We only support string and enum keys
  return null;
  }
 
- Type genericType = typeof(HashSet<>).MakeGenericType(keyType);
- object instance = Activator.CreateInstance(genericType)!;
-
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
  object?[] arguments = new object?[1];
-
- if (source != null)
+ // addMethod can only be null if type is IReadOnlySet<T> rather than ISet<T>.
+ MethodInfo? addMethod = type.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in source)
+ Type genericType = typeof(HashSet<>).MakeGenericType(elementType);
+ object instance = Activator.CreateInstance(genericType)!;
+ addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup);
+
+ if (source != null)
  {
- arguments[0] = item;
- addMethod.Invoke(instance, arguments);
+ foreach (object? item in source)
+ {
+ arguments[0] = item;
+ addMethod!.Invoke(instance, arguments);
+ }
  }
+
+ source = (IEnumerable)instance;
  }
 
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
  foreach (IConfigurationSection section in config.GetChildren())
  {
  var itemBindingPoint = new BindingPoint();
@@ -777,7 +794,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  arguments[0] = itemBindingPoint.Value;
 
- addMethod.Invoke(instance, arguments);
+ addMethod.Invoke(source, arguments);
  }
  }
  catch (Exception ex)
@@ -790,7 +807,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  }
  }
 
- return instance;
+ return source;
  }
 
  [RequiresUnreferencedCode(TrimmingWarningMessage)]

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/ConfigurationBinderTests.cs

@@ -812,7 +812,7 @@ public void CanBindISetNoSetter()
 
  var config = configurationBuilder.Build();
 
- var options = config.Get<ComplexOptions>()!;
+ var options = config.Get<ComplexOptions>(o => o.ErrorOnUnknownConfiguration = true)!;
 
  Assert.Equal(2, options.ISetNoSetter.Count);
  Assert.Equal("Yo1", options.ISetNoSetter.ElementAt(0));
@@ -937,8 +937,6 @@ public void CanBindInstantiatedReadOnlyDictionary2()
  Assert.Equal(2, options.Items["existing-item2"]);
  Assert.Equal(3, options.Items["item3"]);
  Assert.Equal(4, options.Items["item4"]);
-
-
  }
 
  [Fact]
@@ -956,6 +954,7 @@ public void BindInstantiatedIReadOnlyDictionary_CreatesCopyOfOriginal()
 
  var options = config.Get<ConfigWithInstantiatedIReadOnlyDictionary>()!;
 
+ // Readonly dictionary with instantiated value cannot be mutated by the configuration
  Assert.Equal(3, options.Dictionary.Count);
 
  // does not overwrite original
@@ -1027,6 +1026,7 @@ public void CanBindInstantiatedReadOnlyDictionary()
  var options = config.Get<ComplexOptions>()!;
 
  var resultingDictionary = options.InstantiatedReadOnlyDictionaryWithWithSomeValues;
+
  Assert.Equal(4, resultingDictionary.Count);
  Assert.Equal(1, resultingDictionary["existing-item1"]);
  Assert.Equal(2, resultingDictionary["existing-item2"]);

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

@@ -315,12 +315,15 @@ private static void BindInstance(
  }
 
  // for sets and read-only set interfaces, we clone what's there into a new collection, if we can
- if (TypeIsASetInterface(type) && !bindingPoint.IsReadOnly)
+ if (TypeIsASetInterface(type))
  {
- object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
- if (newValue != null)
+ if (!bindingPoint.IsReadOnly || bindingPoint.Value is not null)
  {
- bindingPoint.SetValue(newValue);
+ object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
+ if (!bindingPoint.IsReadOnly && newValue != null)
+ {
+ bindingPoint.SetValue(newValue);
+ }
  }
 
  return;
@@ -530,33 +533,41 @@ private static bool CanBindToTheseConstructorParameters(ParameterInfo[] construc
  return null;
  }
 
- Type genericType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
- Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
- PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
- PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
-
- object dictionary = Activator.CreateInstance(genericType)!;
-
- var orig = source as IEnumerable;
- object?[] arguments = new object?[2];
-
- if (orig != null)
+ // addMethod can only be null if dictionaryType is IReadOnlyDictionary<TKey, TValue> rather than IDictionary<TKey, TValue>.
+ MethodInfo? addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in orig)
+ dictionaryType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
+ var dictionary = Activator.CreateInstance(dictionaryType);
+ addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+
+ var orig = source as IEnumerable;
+ if (orig is not null)
  {
- object? k = keyMethod.GetMethod!.Invoke(item, null);
- object? v = valueMethod.GetMethod!.Invoke(item, null);
- arguments[0] = k;
- arguments[1] = v;
- addMethod.Invoke(dictionary, arguments);
+ Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
+ PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
+ PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
+ object?[] arguments = new object?[2];
+
+ foreach (object? item in orig)
+ {
+ object? k = keyMethod.GetMethod!.Invoke(item, null);
+ object? v = valueMethod.GetMethod!.Invoke(item, null);
+ arguments[0] = k;
+ arguments[1] = v;
+ addMethod!.Invoke(dictionary, arguments);
+ }
  }
+
+ source = dictionary;
  }
 
- BindDictionary(dictionary, genericType, config, options);
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
+ BindDictionary(source, dictionaryType, config, options);
 
- return dictionary;
+ return source;
  }
 
  // Binds and potentially overwrites a dictionary object.
@@ -737,32 +748,38 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  Type elementType = type.GetGenericArguments()[0];
 
-Type keyType = type.GenericTypeArguments[0];
+bool keyTypeIsEnum = elementType.IsEnum;
 
- bool keyTypeIsEnum = keyType.IsEnum;
-
- if (keyType != typeof(string) && !keyTypeIsEnum)
+ if (elementType != typeof(string) && !keyTypeIsEnum)
  {
  // We only support string and enum keys
  return null;
  }
 
- Type genericType = typeof(HashSet<>).MakeGenericType(keyType);
- object instance = Activator.CreateInstance(genericType)!;
-
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
  object?[] arguments = new object?[1];
-
- if (source != null)
+ // addMethod can only be null if type is IReadOnlySet<T> rather than ISet<T>.
+ MethodInfo? addMethod = type.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in source)
+ Type genericType = typeof(HashSet<>).MakeGenericType(elementType);
+ object instance = Activator.CreateInstance(genericType)!;
+ addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup);
+
+ if (source != null)
  {
- arguments[0] = item;
- addMethod.Invoke(instance, arguments);
+ foreach (object? item in source)
+ {
+ arguments[0] = item;
+ addMethod!.Invoke(instance, arguments);
+ }
  }
+
+ source = (IEnumerable)instance;
  }
 
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
  foreach (IConfigurationSection section in config.GetChildren())
  {
  var itemBindingPoint = new BindingPoint();
@@ -777,7 +794,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  arguments[0] = itemBindingPoint.Value;
 
- addMethod.Invoke(instance, arguments);
+ addMethod.Invoke(source, arguments);
  }
  }
  catch (Exception ex)
@@ -790,7 +807,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  }
  }
 
- return instance;
+ return source;
  }
 
  [RequiresUnreferencedCode(TrimmingWarningMessage)]

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/ConfigurationBinderTests.cs

@@ -812,7 +812,7 @@ public void CanBindISetNoSetter()
 
  var config = configurationBuilder.Build();
 
- var options = config.Get<ComplexOptions>()!;
+ var options = config.Get<ComplexOptions>(o => o.ErrorOnUnknownConfiguration = true)!;
 
  Assert.Equal(2, options.ISetNoSetter.Count);
  Assert.Equal("Yo1", options.ISetNoSetter.ElementAt(0));
@@ -937,8 +937,6 @@ public void CanBindInstantiatedReadOnlyDictionary2()
  Assert.Equal(2, options.Items["existing-item2"]);
  Assert.Equal(3, options.Items["item3"]);
  Assert.Equal(4, options.Items["item4"]);
-
-
  }
 
  [Fact]
@@ -956,6 +954,7 @@ public void BindInstantiatedIReadOnlyDictionary_CreatesCopyOfOriginal()
 
  var options = config.Get<ConfigWithInstantiatedIReadOnlyDictionary>()!;
 
+ // Readonly dictionary with instantiated value cannot be mutated by the configuration
  Assert.Equal(3, options.Dictionary.Count);
 
  // does not overwrite original
@@ -1027,6 +1026,7 @@ public void CanBindInstantiatedReadOnlyDictionary()
  var options = config.Get<ComplexOptions>()!;
 
  var resultingDictionary = options.InstantiatedReadOnlyDictionaryWithWithSomeValues;
+
  Assert.Equal(4, resultingDictionary.Count);
  Assert.Equal(1, resultingDictionary["existing-item1"]);
  Assert.Equal(2, resultingDictionary["existing-item2"]);

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

@@ -315,12 +315,15 @@ private static void BindInstance(
  }
 
  // for sets and read-only set interfaces, we clone what's there into a new collection, if we can
- if (TypeIsASetInterface(type) && !bindingPoint.IsReadOnly)
+ if (TypeIsASetInterface(type))
  {
- object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
- if (newValue != null)
+ if (!bindingPoint.IsReadOnly || bindingPoint.Value is not null)
  {
- bindingPoint.SetValue(newValue);
+ object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
+ if (!bindingPoint.IsReadOnly && newValue != null)
+ {
+ bindingPoint.SetValue(newValue);
+ }
  }
 
  return;
@@ -530,33 +533,41 @@ private static bool CanBindToTheseConstructorParameters(ParameterInfo[] construc
  return null;
  }
 
- Type genericType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
- Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
- PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
- PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
-
- object dictionary = Activator.CreateInstance(genericType)!;
-
- var orig = source as IEnumerable;
- object?[] arguments = new object?[2];
-
- if (orig != null)
+ // addMethod can only be null if dictionaryType is IReadOnlyDictionary<TKey, TValue> rather than IDictionary<TKey, TValue>.
+ MethodInfo? addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in orig)
+ dictionaryType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
+ var dictionary = Activator.CreateInstance(dictionaryType);
+ addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+
+ var orig = source as IEnumerable;
+ if (orig is not null)
  {
- object? k = keyMethod.GetMethod!.Invoke(item, null);
- object? v = valueMethod.GetMethod!.Invoke(item, null);
- arguments[0] = k;
- arguments[1] = v;
- addMethod.Invoke(dictionary, arguments);
+ Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
+ PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
+ PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
+ object?[] arguments = new object?[2];
+
+ foreach (object? item in orig)
+ {
+ object? k = keyMethod.GetMethod!.Invoke(item, null);
+ object? v = valueMethod.GetMethod!.Invoke(item, null);
+ arguments[0] = k;
+ arguments[1] = v;
+ addMethod!.Invoke(dictionary, arguments);
+ }
  }
+
+ source = dictionary;
  }
 
- BindDictionary(dictionary, genericType, config, options);
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
+ BindDictionary(source, dictionaryType, config, options);
 
- return dictionary;
+ return source;
  }
 
  // Binds and potentially overwrites a dictionary object.
@@ -737,32 +748,38 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  Type elementType = type.GetGenericArguments()[0];
 
-Type keyType = type.GenericTypeArguments[0];
+bool keyTypeIsEnum = elementType.IsEnum;
 
- bool keyTypeIsEnum = keyType.IsEnum;
-
- if (keyType != typeof(string) && !keyTypeIsEnum)
+ if (elementType != typeof(string) && !keyTypeIsEnum)
  {
  // We only support string and enum keys
  return null;
  }
 
- Type genericType = typeof(HashSet<>).MakeGenericType(keyType);
- object instance = Activator.CreateInstance(genericType)!;
-
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
  object?[] arguments = new object?[1];
-
- if (source != null)
+ // addMethod can only be null if type is IReadOnlySet<T> rather than ISet<T>.
+ MethodInfo? addMethod = type.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in source)
+ Type genericType = typeof(HashSet<>).MakeGenericType(elementType);
+ object instance = Activator.CreateInstance(genericType)!;
+ addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup);
+
+ if (source != null)
  {
- arguments[0] = item;
- addMethod.Invoke(instance, arguments);
+ foreach (object? item in source)
+ {
+ arguments[0] = item;
+ addMethod!.Invoke(instance, arguments);
+ }
  }
+
+ source = (IEnumerable)instance;
  }
 
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
  foreach (IConfigurationSection section in config.GetChildren())
  {
  var itemBindingPoint = new BindingPoint();
@@ -777,7 +794,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  arguments[0] = itemBindingPoint.Value;
 
- addMethod.Invoke(instance, arguments);
+ addMethod.Invoke(source, arguments);
  }
  }
  catch (Exception ex)
@@ -790,7 +807,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  }
  }
 
- return instance;
+ return source;
  }
 
  [RequiresUnreferencedCode(TrimmingWarningMessage)]

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/ConfigurationBinderTests.cs

@@ -812,7 +812,7 @@ public void CanBindISetNoSetter()
 
  var config = configurationBuilder.Build();
 
- var options = config.Get<ComplexOptions>()!;
+ var options = config.Get<ComplexOptions>(o => o.ErrorOnUnknownConfiguration = true)!;
 
  Assert.Equal(2, options.ISetNoSetter.Count);
  Assert.Equal("Yo1", options.ISetNoSetter.ElementAt(0));
@@ -937,8 +937,6 @@ public void CanBindInstantiatedReadOnlyDictionary2()
  Assert.Equal(2, options.Items["existing-item2"]);
  Assert.Equal(3, options.Items["item3"]);
  Assert.Equal(4, options.Items["item4"]);
-
-
  }
 
  [Fact]
@@ -956,6 +954,7 @@ public void BindInstantiatedIReadOnlyDictionary_CreatesCopyOfOriginal()
 
  var options = config.Get<ConfigWithInstantiatedIReadOnlyDictionary>()!;
 
+ // Readonly dictionary with instantiated value cannot be mutated by the configuration
  Assert.Equal(3, options.Dictionary.Count);
 
  // does not overwrite original
@@ -1027,6 +1026,7 @@ public void CanBindInstantiatedReadOnlyDictionary()
  var options = config.Get<ComplexOptions>()!;
 
  var resultingDictionary = options.InstantiatedReadOnlyDictionaryWithWithSomeValues;
+
  Assert.Equal(4, resultingDictionary.Count);
  Assert.Equal(1, resultingDictionary["existing-item1"]);
  Assert.Equal(2, resultingDictionary["existing-item2"]);

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

@@ -315,12 +315,15 @@ private static void BindInstance(
  }
 
  // for sets and read-only set interfaces, we clone what's there into a new collection, if we can
- if (TypeIsASetInterface(type) && !bindingPoint.IsReadOnly)
+ if (TypeIsASetInterface(type))
  {
- object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
- if (newValue != null)
+ if (!bindingPoint.IsReadOnly || bindingPoint.Value is not null)
  {
- bindingPoint.SetValue(newValue);
+ object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
+ if (!bindingPoint.IsReadOnly && newValue != null)
+ {
+ bindingPoint.SetValue(newValue);
+ }
  }
 
  return;
@@ -530,33 +533,41 @@ private static bool CanBindToTheseConstructorParameters(ParameterInfo[] construc
  return null;
  }
 
- Type genericType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
- Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
- PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
- PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
-
- object dictionary = Activator.CreateInstance(genericType)!;
-
- var orig = source as IEnumerable;
- object?[] arguments = new object?[2];
-
- if (orig != null)
+ // addMethod can only be null if dictionaryType is IReadOnlyDictionary<TKey, TValue> rather than IDictionary<TKey, TValue>.
+ MethodInfo? addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in orig)
+ dictionaryType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
+ var dictionary = Activator.CreateInstance(dictionaryType);
+ addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+
+ var orig = source as IEnumerable;
+ if (orig is not null)
  {
- object? k = keyMethod.GetMethod!.Invoke(item, null);
- object? v = valueMethod.GetMethod!.Invoke(item, null);
- arguments[0] = k;
- arguments[1] = v;
- addMethod.Invoke(dictionary, arguments);
+ Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
+ PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
+ PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
+ object?[] arguments = new object?[2];
+
+ foreach (object? item in orig)
+ {
+ object? k = keyMethod.GetMethod!.Invoke(item, null);
+ object? v = valueMethod.GetMethod!.Invoke(item, null);
+ arguments[0] = k;
+ arguments[1] = v;
+ addMethod!.Invoke(dictionary, arguments);
+ }
  }
+
+ source = dictionary;
  }
 
- BindDictionary(dictionary, genericType, config, options);
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
+ BindDictionary(source, dictionaryType, config, options);
 
- return dictionary;
+ return source;
  }
 
  // Binds and potentially overwrites a dictionary object.
@@ -737,32 +748,38 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  Type elementType = type.GetGenericArguments()[0];
 
-Type keyType = type.GenericTypeArguments[0];
+bool keyTypeIsEnum = elementType.IsEnum;
 
- bool keyTypeIsEnum = keyType.IsEnum;
-
- if (keyType != typeof(string) && !keyTypeIsEnum)
+ if (elementType != typeof(string) && !keyTypeIsEnum)
  {
  // We only support string and enum keys
  return null;
  }
 
- Type genericType = typeof(HashSet<>).MakeGenericType(keyType);
- object instance = Activator.CreateInstance(genericType)!;
-
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
  object?[] arguments = new object?[1];
-
- if (source != null)
+ // addMethod can only be null if type is IReadOnlySet<T> rather than ISet<T>.
+ MethodInfo? addMethod = type.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in source)
+ Type genericType = typeof(HashSet<>).MakeGenericType(elementType);
+ object instance = Activator.CreateInstance(genericType)!;
+ addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup);
+
+ if (source != null)
  {
- arguments[0] = item;
- addMethod.Invoke(instance, arguments);
+ foreach (object? item in source)
+ {
+ arguments[0] = item;
+ addMethod!.Invoke(instance, arguments);
+ }
  }
+
+ source = (IEnumerable)instance;
  }
 
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
  foreach (IConfigurationSection section in config.GetChildren())
  {
  var itemBindingPoint = new BindingPoint();
@@ -777,7 +794,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  arguments[0] = itemBindingPoint.Value;
 
- addMethod.Invoke(instance, arguments);
+ addMethod.Invoke(source, arguments);
  }
  }
  catch (Exception ex)
@@ -790,7 +807,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  }
  }
 
- return instance;
+ return source;
  }
 
  [RequiresUnreferencedCode(TrimmingWarningMessage)]

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/ConfigurationBinderTests.cs

@@ -812,7 +812,7 @@ public void CanBindISetNoSetter()
 
  var config = configurationBuilder.Build();
 
- var options = config.Get<ComplexOptions>()!;
+ var options = config.Get<ComplexOptions>(o => o.ErrorOnUnknownConfiguration = true)!;
 
  Assert.Equal(2, options.ISetNoSetter.Count);
  Assert.Equal("Yo1", options.ISetNoSetter.ElementAt(0));
@@ -937,8 +937,6 @@ public void CanBindInstantiatedReadOnlyDictionary2()
  Assert.Equal(2, options.Items["existing-item2"]);
  Assert.Equal(3, options.Items["item3"]);
  Assert.Equal(4, options.Items["item4"]);
-
-
  }
 
  [Fact]
@@ -956,6 +954,7 @@ public void BindInstantiatedIReadOnlyDictionary_CreatesCopyOfOriginal()
 
  var options = config.Get<ConfigWithInstantiatedIReadOnlyDictionary>()!;
 
+ // Readonly dictionary with instantiated value cannot be mutated by the configuration
  Assert.Equal(3, options.Dictionary.Count);
 
  // does not overwrite original
@@ -1027,6 +1026,7 @@ public void CanBindInstantiatedReadOnlyDictionary()
  var options = config.Get<ComplexOptions>()!;
 
  var resultingDictionary = options.InstantiatedReadOnlyDictionaryWithWithSomeValues;
+
  Assert.Equal(4, resultingDictionary.Count);
  Assert.Equal(1, resultingDictionary["existing-item1"]);
  Assert.Equal(2, resultingDictionary["existing-item2"]);

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

@@ -315,12 +315,15 @@ private static void BindInstance(
  }
 
  // for sets and read-only set interfaces, we clone what's there into a new collection, if we can
- if (TypeIsASetInterface(type) && !bindingPoint.IsReadOnly)
+ if (TypeIsASetInterface(type))
  {
- object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
- if (newValue != null)
+ if (!bindingPoint.IsReadOnly || bindingPoint.Value is not null)
  {
- bindingPoint.SetValue(newValue);
+ object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
+ if (!bindingPoint.IsReadOnly && newValue != null)
+ {
+ bindingPoint.SetValue(newValue);
+ }
  }
 
  return;
@@ -530,33 +533,41 @@ private static bool CanBindToTheseConstructorParameters(ParameterInfo[] construc
  return null;
  }
 
- Type genericType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
- Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
- PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
- PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
-
- object dictionary = Activator.CreateInstance(genericType)!;
-
- var orig = source as IEnumerable;
- object?[] arguments = new object?[2];
-
- if (orig != null)
+ // addMethod can only be null if dictionaryType is IReadOnlyDictionary<TKey, TValue> rather than IDictionary<TKey, TValue>.
+ MethodInfo? addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in orig)
+ dictionaryType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
+ var dictionary = Activator.CreateInstance(dictionaryType);
+ addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+
+ var orig = source as IEnumerable;
+ if (orig is not null)
  {
- object? k = keyMethod.GetMethod!.Invoke(item, null);
- object? v = valueMethod.GetMethod!.Invoke(item, null);
- arguments[0] = k;
- arguments[1] = v;
- addMethod.Invoke(dictionary, arguments);
+ Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
+ PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
+ PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
+ object?[] arguments = new object?[2];
+
+ foreach (object? item in orig)
+ {
+ object? k = keyMethod.GetMethod!.Invoke(item, null);
+ object? v = valueMethod.GetMethod!.Invoke(item, null);
+ arguments[0] = k;
+ arguments[1] = v;
+ addMethod!.Invoke(dictionary, arguments);
+ }
  }
+
+ source = dictionary;
  }
 
- BindDictionary(dictionary, genericType, config, options);
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
+ BindDictionary(source, dictionaryType, config, options);
 
- return dictionary;
+ return source;
  }
 
  // Binds and potentially overwrites a dictionary object.
@@ -737,32 +748,38 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  Type elementType = type.GetGenericArguments()[0];
 
-Type keyType = type.GenericTypeArguments[0];
+bool keyTypeIsEnum = elementType.IsEnum;
 
- bool keyTypeIsEnum = keyType.IsEnum;
-
- if (keyType != typeof(string) && !keyTypeIsEnum)
+ if (elementType != typeof(string) && !keyTypeIsEnum)
  {
  // We only support string and enum keys
  return null;
  }
 
- Type genericType = typeof(HashSet<>).MakeGenericType(keyType);
- object instance = Activator.CreateInstance(genericType)!;
-
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
  object?[] arguments = new object?[1];
-
- if (source != null)
+ // addMethod can only be null if type is IReadOnlySet<T> rather than ISet<T>.
+ MethodInfo? addMethod = type.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in source)
+ Type genericType = typeof(HashSet<>).MakeGenericType(elementType);
+ object instance = Activator.CreateInstance(genericType)!;
+ addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup);
+
+ if (source != null)
  {
- arguments[0] = item;
- addMethod.Invoke(instance, arguments);
+ foreach (object? item in source)
+ {
+ arguments[0] = item;
+ addMethod!.Invoke(instance, arguments);
+ }
  }
+
+ source = (IEnumerable)instance;
  }
 
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
  foreach (IConfigurationSection section in config.GetChildren())
  {
  var itemBindingPoint = new BindingPoint();
@@ -777,7 +794,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  arguments[0] = itemBindingPoint.Value;
 
- addMethod.Invoke(instance, arguments);
+ addMethod.Invoke(source, arguments);
  }
  }
  catch (Exception ex)
@@ -790,7 +807,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  }
  }
 
- return instance;
+ return source;
  }
 
  [RequiresUnreferencedCode(TrimmingWarningMessage)]

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/ConfigurationBinderTests.cs

@@ -812,7 +812,7 @@ public void CanBindISetNoSetter()
 
  var config = configurationBuilder.Build();
 
- var options = config.Get<ComplexOptions>()!;
+ var options = config.Get<ComplexOptions>(o => o.ErrorOnUnknownConfiguration = true)!;
 
  Assert.Equal(2, options.ISetNoSetter.Count);
  Assert.Equal("Yo1", options.ISetNoSetter.ElementAt(0));
@@ -937,8 +937,6 @@ public void CanBindInstantiatedReadOnlyDictionary2()
  Assert.Equal(2, options.Items["existing-item2"]);
  Assert.Equal(3, options.Items["item3"]);
  Assert.Equal(4, options.Items["item4"]);
-
-
  }
 
  [Fact]
@@ -956,6 +954,7 @@ public void BindInstantiatedIReadOnlyDictionary_CreatesCopyOfOriginal()
 
  var options = config.Get<ConfigWithInstantiatedIReadOnlyDictionary>()!;
 
+ // Readonly dictionary with instantiated value cannot be mutated by the configuration
  Assert.Equal(3, options.Dictionary.Count);
 
  // does not overwrite original
@@ -1027,6 +1026,7 @@ public void CanBindInstantiatedReadOnlyDictionary()
  var options = config.Get<ComplexOptions>()!;
 
  var resultingDictionary = options.InstantiatedReadOnlyDictionaryWithWithSomeValues;
+
  Assert.Equal(4, resultingDictionary.Count);
  Assert.Equal(1, resultingDictionary["existing-item1"]);
  Assert.Equal(2, resultingDictionary["existing-item2"]);

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

@@ -315,12 +315,15 @@ private static void BindInstance(
  }
 
  // for sets and read-only set interfaces, we clone what's there into a new collection, if we can
- if (TypeIsASetInterface(type) && !bindingPoint.IsReadOnly)
+ if (TypeIsASetInterface(type))
  {
- object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
- if (newValue != null)
+ if (!bindingPoint.IsReadOnly || bindingPoint.Value is not null)
  {
- bindingPoint.SetValue(newValue);
+ object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
+ if (!bindingPoint.IsReadOnly && newValue != null)
+ {
+ bindingPoint.SetValue(newValue);
+ }
  }
 
  return;
@@ -530,33 +533,41 @@ private static bool CanBindToTheseConstructorParameters(ParameterInfo[] construc
  return null;
  }
 
- Type genericType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
- Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
- PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
- PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
-
- object dictionary = Activator.CreateInstance(genericType)!;
-
- var orig = source as IEnumerable;
- object?[] arguments = new object?[2];
-
- if (orig != null)
+ // addMethod can only be null if dictionaryType is IReadOnlyDictionary<TKey, TValue> rather than IDictionary<TKey, TValue>.
+ MethodInfo? addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in orig)
+ dictionaryType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
+ var dictionary = Activator.CreateInstance(dictionaryType);
+ addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+
+ var orig = source as IEnumerable;
+ if (orig is not null)
  {
- object? k = keyMethod.GetMethod!.Invoke(item, null);
- object? v = valueMethod.GetMethod!.Invoke(item, null);
- arguments[0] = k;
- arguments[1] = v;
- addMethod.Invoke(dictionary, arguments);
+ Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
+ PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
+ PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
+ object?[] arguments = new object?[2];
+
+ foreach (object? item in orig)
+ {
+ object? k = keyMethod.GetMethod!.Invoke(item, null);
+ object? v = valueMethod.GetMethod!.Invoke(item, null);
+ arguments[0] = k;
+ arguments[1] = v;
+ addMethod!.Invoke(dictionary, arguments);
+ }
  }
+
+ source = dictionary;
  }
 
- BindDictionary(dictionary, genericType, config, options);
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
+ BindDictionary(source, dictionaryType, config, options);
 
- return dictionary;
+ return source;
  }
 
  // Binds and potentially overwrites a dictionary object.
@@ -737,32 +748,38 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  Type elementType = type.GetGenericArguments()[0];
 
-Type keyType = type.GenericTypeArguments[0];
+bool keyTypeIsEnum = elementType.IsEnum;
 
- bool keyTypeIsEnum = keyType.IsEnum;
-
- if (keyType != typeof(string) && !keyTypeIsEnum)
+ if (elementType != typeof(string) && !keyTypeIsEnum)
  {
  // We only support string and enum keys
  return null;
  }
 
- Type genericType = typeof(HashSet<>).MakeGenericType(keyType);
- object instance = Activator.CreateInstance(genericType)!;
-
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
  object?[] arguments = new object?[1];
-
- if (source != null)
+ // addMethod can only be null if type is IReadOnlySet<T> rather than ISet<T>.
+ MethodInfo? addMethod = type.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in source)
+ Type genericType = typeof(HashSet<>).MakeGenericType(elementType);
+ object instance = Activator.CreateInstance(genericType)!;
+ addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup);
+
+ if (source != null)
  {
- arguments[0] = item;
- addMethod.Invoke(instance, arguments);
+ foreach (object? item in source)
+ {
+ arguments[0] = item;
+ addMethod!.Invoke(instance, arguments);
+ }
  }
+
+ source = (IEnumerable)instance;
  }
 
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
  foreach (IConfigurationSection section in config.GetChildren())
  {
  var itemBindingPoint = new BindingPoint();
@@ -777,7 +794,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  arguments[0] = itemBindingPoint.Value;
 
- addMethod.Invoke(instance, arguments);
+ addMethod.Invoke(source, arguments);
  }
  }
  catch (Exception ex)
@@ -790,7 +807,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  }
  }
 
- return instance;
+ return source;
  }
 
  [RequiresUnreferencedCode(TrimmingWarningMessage)]

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/ConfigurationBinderTests.cs

@@ -812,7 +812,7 @@ public void CanBindISetNoSetter()
 
  var config = configurationBuilder.Build();
 
- var options = config.Get<ComplexOptions>()!;
+ var options = config.Get<ComplexOptions>(o => o.ErrorOnUnknownConfiguration = true)!;
 
  Assert.Equal(2, options.ISetNoSetter.Count);
  Assert.Equal("Yo1", options.ISetNoSetter.ElementAt(0));
@@ -937,8 +937,6 @@ public void CanBindInstantiatedReadOnlyDictionary2()
  Assert.Equal(2, options.Items["existing-item2"]);
  Assert.Equal(3, options.Items["item3"]);
  Assert.Equal(4, options.Items["item4"]);
-
-
  }
 
  [Fact]
@@ -956,6 +954,7 @@ public void BindInstantiatedIReadOnlyDictionary_CreatesCopyOfOriginal()
 
  var options = config.Get<ConfigWithInstantiatedIReadOnlyDictionary>()!;
 
+ // Readonly dictionary with instantiated value cannot be mutated by the configuration
  Assert.Equal(3, options.Dictionary.Count);
 
  // does not overwrite original
@@ -1027,6 +1026,7 @@ public void CanBindInstantiatedReadOnlyDictionary()
  var options = config.Get<ComplexOptions>()!;
 
  var resultingDictionary = options.InstantiatedReadOnlyDictionaryWithWithSomeValues;
+
  Assert.Equal(4, resultingDictionary.Count);
  Assert.Equal(1, resultingDictionary["existing-item1"]);
  Assert.Equal(2, resultingDictionary["existing-item2"]);

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

@@ -315,12 +315,15 @@ private static void BindInstance(
  }
 
  // for sets and read-only set interfaces, we clone what's there into a new collection, if we can
- if (TypeIsASetInterface(type) && !bindingPoint.IsReadOnly)
+ if (TypeIsASetInterface(type))
  {
- object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
- if (newValue != null)
+ if (!bindingPoint.IsReadOnly || bindingPoint.Value is not null)
  {
- bindingPoint.SetValue(newValue);
+ object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
+ if (!bindingPoint.IsReadOnly && newValue != null)
+ {
+ bindingPoint.SetValue(newValue);
+ }
  }
 
  return;
@@ -530,33 +533,41 @@ private static bool CanBindToTheseConstructorParameters(ParameterInfo[] construc
  return null;
  }
 
- Type genericType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
- Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
- PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
- PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
-
- object dictionary = Activator.CreateInstance(genericType)!;
-
- var orig = source as IEnumerable;
- object?[] arguments = new object?[2];
-
- if (orig != null)
+ // addMethod can only be null if dictionaryType is IReadOnlyDictionary<TKey, TValue> rather than IDictionary<TKey, TValue>.
+ MethodInfo? addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in orig)
+ dictionaryType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
+ var dictionary = Activator.CreateInstance(dictionaryType);
+ addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+
+ var orig = source as IEnumerable;
+ if (orig is not null)
  {
- object? k = keyMethod.GetMethod!.Invoke(item, null);
- object? v = valueMethod.GetMethod!.Invoke(item, null);
- arguments[0] = k;
- arguments[1] = v;
- addMethod.Invoke(dictionary, arguments);
+ Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
+ PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
+ PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
+ object?[] arguments = new object?[2];
+
+ foreach (object? item in orig)
+ {
+ object? k = keyMethod.GetMethod!.Invoke(item, null);
+ object? v = valueMethod.GetMethod!.Invoke(item, null);
+ arguments[0] = k;
+ arguments[1] = v;
+ addMethod!.Invoke(dictionary, arguments);
+ }
  }
+
+ source = dictionary;
  }
 
- BindDictionary(dictionary, genericType, config, options);
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
+ BindDictionary(source, dictionaryType, config, options);
 
- return dictionary;
+ return source;
  }
 
  // Binds and potentially overwrites a dictionary object.
@@ -737,32 +748,38 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  Type elementType = type.GetGenericArguments()[0];
 
-Type keyType = type.GenericTypeArguments[0];
+bool keyTypeIsEnum = elementType.IsEnum;
 
- bool keyTypeIsEnum = keyType.IsEnum;
-
- if (keyType != typeof(string) && !keyTypeIsEnum)
+ if (elementType != typeof(string) && !keyTypeIsEnum)
  {
  // We only support string and enum keys
  return null;
  }
 
- Type genericType = typeof(HashSet<>).MakeGenericType(keyType);
- object instance = Activator.CreateInstance(genericType)!;
-
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
  object?[] arguments = new object?[1];
-
- if (source != null)
+ // addMethod can only be null if type is IReadOnlySet<T> rather than ISet<T>.
+ MethodInfo? addMethod = type.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in source)
+ Type genericType = typeof(HashSet<>).MakeGenericType(elementType);
+ object instance = Activator.CreateInstance(genericType)!;
+ addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup);
+
+ if (source != null)
  {
- arguments[0] = item;
- addMethod.Invoke(instance, arguments);
+ foreach (object? item in source)
+ {
+ arguments[0] = item;
+ addMethod!.Invoke(instance, arguments);
+ }
  }
+
+ source = (IEnumerable)instance;
  }
 
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
  foreach (IConfigurationSection section in config.GetChildren())
  {
  var itemBindingPoint = new BindingPoint();
@@ -777,7 +794,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  arguments[0] = itemBindingPoint.Value;
 
- addMethod.Invoke(instance, arguments);
+ addMethod.Invoke(source, arguments);
  }
  }
  catch (Exception ex)
@@ -790,7 +807,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  }
  }
 
- return instance;
+ return source;
  }
 
  [RequiresUnreferencedCode(TrimmingWarningMessage)]

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/ConfigurationBinderTests.cs

@@ -812,7 +812,7 @@ public void CanBindISetNoSetter()
 
  var config = configurationBuilder.Build();
 
- var options = config.Get<ComplexOptions>()!;
+ var options = config.Get<ComplexOptions>(o => o.ErrorOnUnknownConfiguration = true)!;
 
  Assert.Equal(2, options.ISetNoSetter.Count);
  Assert.Equal("Yo1", options.ISetNoSetter.ElementAt(0));
@@ -937,8 +937,6 @@ public void CanBindInstantiatedReadOnlyDictionary2()
  Assert.Equal(2, options.Items["existing-item2"]);
  Assert.Equal(3, options.Items["item3"]);
  Assert.Equal(4, options.Items["item4"]);
-
-
  }
 
  [Fact]
@@ -956,6 +954,7 @@ public void BindInstantiatedIReadOnlyDictionary_CreatesCopyOfOriginal()
 
  var options = config.Get<ConfigWithInstantiatedIReadOnlyDictionary>()!;
 
+ // Readonly dictionary with instantiated value cannot be mutated by the configuration
  Assert.Equal(3, options.Dictionary.Count);
 
  // does not overwrite original
@@ -1027,6 +1026,7 @@ public void CanBindInstantiatedReadOnlyDictionary()
  var options = config.Get<ComplexOptions>()!;
 
  var resultingDictionary = options.InstantiatedReadOnlyDictionaryWithWithSomeValues;
+
  Assert.Equal(4, resultingDictionary.Count);
  Assert.Equal(1, resultingDictionary["existing-item1"]);
  Assert.Equal(2, resultingDictionary["existing-item2"]);

src/libraries/Microsoft.Extensions.Configuration.Binder/src/ConfigurationBinder.cs

@@ -315,12 +315,15 @@ private static void BindInstance(
  }
 
  // for sets and read-only set interfaces, we clone what's there into a new collection, if we can
- if (TypeIsASetInterface(type) && !bindingPoint.IsReadOnly)
+ if (TypeIsASetInterface(type))
  {
- object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
- if (newValue != null)
+ if (!bindingPoint.IsReadOnly || bindingPoint.Value is not null)
  {
- bindingPoint.SetValue(newValue);
+ object? newValue = BindSet(type, (IEnumerable?)bindingPoint.Value, config, options);
+ if (!bindingPoint.IsReadOnly && newValue != null)
+ {
+ bindingPoint.SetValue(newValue);
+ }
  }
 
  return;
@@ -530,33 +533,41 @@ private static bool CanBindToTheseConstructorParameters(ParameterInfo[] construc
  return null;
  }
 
- Type genericType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
- Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
- PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
- PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
-
- object dictionary = Activator.CreateInstance(genericType)!;
-
- var orig = source as IEnumerable;
- object?[] arguments = new object?[2];
-
- if (orig != null)
+ // addMethod can only be null if dictionaryType is IReadOnlyDictionary<TKey, TValue> rather than IDictionary<TKey, TValue>.
+ MethodInfo? addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in orig)
+ dictionaryType = typeof(Dictionary<,>).MakeGenericType(keyType, valueType);
+ var dictionary = Activator.CreateInstance(dictionaryType);
+ addMethod = dictionaryType.GetMethod("Add", DeclaredOnlyLookup);
+
+ var orig = source as IEnumerable;
+ if (orig is not null)
  {
- object? k = keyMethod.GetMethod!.Invoke(item, null);
- object? v = valueMethod.GetMethod!.Invoke(item, null);
- arguments[0] = k;
- arguments[1] = v;
- addMethod.Invoke(dictionary, arguments);
+ Type kvpType = typeof(KeyValuePair<,>).MakeGenericType(keyType, valueType);
+ PropertyInfo keyMethod = kvpType.GetProperty("Key", DeclaredOnlyLookup)!;
+ PropertyInfo valueMethod = kvpType.GetProperty("Value", DeclaredOnlyLookup)!;
+ object?[] arguments = new object?[2];
+
+ foreach (object? item in orig)
+ {
+ object? k = keyMethod.GetMethod!.Invoke(item, null);
+ object? v = valueMethod.GetMethod!.Invoke(item, null);
+ arguments[0] = k;
+ arguments[1] = v;
+ addMethod!.Invoke(dictionary, arguments);
+ }
  }
+
+ source = dictionary;
  }
 
- BindDictionary(dictionary, genericType, config, options);
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
+ BindDictionary(source, dictionaryType, config, options);
 
- return dictionary;
+ return source;
  }
 
  // Binds and potentially overwrites a dictionary object.
@@ -737,32 +748,38 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  Type elementType = type.GetGenericArguments()[0];
 
-Type keyType = type.GenericTypeArguments[0];
+bool keyTypeIsEnum = elementType.IsEnum;
 
- bool keyTypeIsEnum = keyType.IsEnum;
-
- if (keyType != typeof(string) && !keyTypeIsEnum)
+ if (elementType != typeof(string) && !keyTypeIsEnum)
  {
  // We only support string and enum keys
  return null;
  }
 
- Type genericType = typeof(HashSet<>).MakeGenericType(keyType);
- object instance = Activator.CreateInstance(genericType)!;
-
- MethodInfo addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup)!;
-
  object?[] arguments = new object?[1];
-
- if (source != null)
+ // addMethod can only be null if type is IReadOnlySet<T> rather than ISet<T>.
+ MethodInfo? addMethod = type.GetMethod("Add", DeclaredOnlyLookup);
+ if (addMethod is null || source is null)
  {
- foreach (object? item in source)
+ Type genericType = typeof(HashSet<>).MakeGenericType(elementType);
+ object instance = Activator.CreateInstance(genericType)!;
+ addMethod = genericType.GetMethod("Add", DeclaredOnlyLookup);
+
+ if (source != null)
  {
- arguments[0] = item;
- addMethod.Invoke(instance, arguments);
+ foreach (object? item in source)
+ {
+ arguments[0] = item;
+ addMethod!.Invoke(instance, arguments);
+ }
  }
+
+ source = (IEnumerable)instance;
  }
 
+ Debug.Assert(source is not null);
+ Debug.Assert(addMethod is not null);
+
  foreach (IConfigurationSection section in config.GetChildren())
  {
  var itemBindingPoint = new BindingPoint();
@@ -777,7 +794,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  {
  arguments[0] = itemBindingPoint.Value;
 
- addMethod.Invoke(instance, arguments);
+ addMethod.Invoke(source, arguments);
  }
  }
  catch (Exception ex)
@@ -790,7 +807,7 @@ private static Array BindArray(Type type, IEnumerable? source, IConfiguration co
  }
  }
 
- return instance;
+ return source;
  }
 
  [RequiresUnreferencedCode(TrimmingWarningMessage)]

src/libraries/Microsoft.Extensions.Configuration.Binder/tests/ConfigurationBinderTests.cs

@@ -812,7 +812,7 @@ public void CanBindISetNoSetter()
 
  var config = configurationBuilder.Build();
 
- var options = config.Get<ComplexOptions>()!;
+ var options = config.Get<ComplexOptions>(o => o.ErrorOnUnknownConfiguration = true)!;
 
  Assert.Equal(2, options.ISetNoSetter.Count);
  Assert.Equal("Yo1", options.ISetNoSetter.ElementAt(0));
@@ -937,8 +937,6 @@ public void CanBindInstantiatedReadOnlyDictionary2()
  Assert.Equal(2, options.Items["existing-item2"]);
  Assert.Equal(3, options.Items["item3"]);
  Assert.Equal(4, options.Items["item4"]);
-
-
  }
 
  [Fact]
@@ -956,6 +954,7 @@ public void BindInstantiatedIReadOnlyDictionary_CreatesCopyOfOriginal()
 
  var options = config.Get<ConfigWithInstantiatedIReadOnlyDictionary>()!;
 
+ // Readonly dictionary with instantiated value cannot be mutated by the configuration
  Assert.Equal(3, options.Dictionary.Count);
 
  // does not overwrite original
@@ -1027,6 +1026,7 @@ public void CanBindInstantiatedReadOnlyDictionary()
  var options = config.Get<ComplexOptions>()!;
 
  var resultingDictionary = options.InstantiatedReadOnlyDictionaryWithWithSomeValues;
+
  Assert.Equal(4, resultingDictionary.Count);
  Assert.Equal(1, resultingDictionary["existing-item1"]);
  Assert.Equal(2, resultingDictionary["existing-item2"]);