Simple Exception Handling

Library that helps developers to handle exceptions outside catch blocks. Typical usages are global exception handlers.

Installation

This library can be installed via NuGet package. Just run the following command:

Install-Package SimpleExceptionHandling

Compatibility

This library is compatible with the folowing frameworks:

• MonoAndroid 1.0;
• MonoTouch 1.0;
• .NET Framework 2.0
• .NET Framework 3.5
• .NET Framework 4.0
• .NET Framework 4.5
• .NET Core 5.0;
• .NET Standard 1.0;
• Portable Class Library (.NETFramework 4.0, Silverlight 5.0, Windows 8.0, WindowsPhone 8.0, WindowsPhoneApp 8.1);
• Portable Class Library (.NETFramework 4.5, Windows 8.0, WindowsPhoneApp 8.1);
• WindowsPhoneApp 8.1;
• Xamarin.iOS 1.0;
• Xamarin.TVOS 1.0;

Tipical usage

This is a usage example for Web API 2:

usingSimpleExceptionHandling;publicclassGlobalExceptionHandler:ExceptionHandler{privatestaticreadonlyIHandlingConfiguration<ExceptionHandlerContext,ResponseMessageResult>HandlingConfiguration=Handling.Prepare<ExceptionHandlerContext,ResponseMessageResult>().On<ValidationException>((ex,i)=>{returnHandling.Handled(i.Parameter.Request.CreateBadRequestResult(ex.ValidationErrors.Select(
e =>newKeyValuePair<string,string[]>(e.Key,e.Messages.ToArray()))));}).On<BusinessException>((ex,i)=>{returnHandling.Handled(i.Parameter.Request.CreateConflictResult(ex.Message));}).On<GenericException>((ex,i)=>{returnHandling.Handled(i.Parameter.Request.CreateInternalServerErrorResult(ex.Message));}).On<ExternalServiceException>((ex,i)=>{returnHandling.Handled(i.Parameter.Request.CreateBadGatewayResult());}).On<TimeoutException>((ex,i)=>{returnHandling.Handled(i.Parameter.Request.CreateGatewayTimeoutResult());}).On<NotImplementedException>((ex,i)=>{returnHandling.Handled(i.Parameter.Request.CreateNotImplementedResult());});publicoverrideboolShouldHandle(ExceptionHandlerContextcontext){returntrue;}publicoverridevoidHandle(ExceptionHandlerContextcontext){varresult=HandlingConfiguration.Catch(context.Exception,context,false);if(result.Handled){context.Result=result.Result;}else{base.Handle(context);}}}

Basic usage

Here is a simple example of handling exceptions by their types:

publicstaticvoidBasicExceptionHandling(stringparam01){stringhandlerName=null;varconfiguration=Handling.Prepare().On<ArgumentNullException>(ex =>{handlerName=$"ArgumentNullException[ParamName={ex.ParamName}]";}).On<ArgumentException>(ex =>{handlerName=$"ArgumentException[ParamName={ex.ParamName}]";});varresult=configuration.Catch(newArgumentNullException(nameof(param01)));Console.WriteLine($"Handler[Handled={result.Handled}] -> '{handlerName}'");// Handler[Handled=True] -> 'ArgumentNullException[ParamName=param01]'handlerName=null;result=configuration.Catch(newArgumentOutOfRangeException(nameof(param01)));Console.WriteLine($"Handler[Handled={result.Handled}] -> '{handlerName}'");// Handler[Handled=True] -> 'ArgumentException[ParamName=param01]'handlerName=null;result=configuration.Catch(newException(),throwIfNotHandled:false);Console.WriteLine($"Handler[Handled={result.Handled}] -> '{handlerName}'");// Handler[Handled=False] -> ''}

Input Parameter and Result

In this example, a parameter is passed as an argument of the Catch method, and a result is returned by handlers. One of the handlers will be invoked but won't be considered to handle the exception:

publicstaticvoidInputAndResultExceptionHandling(stringparam01){varconfiguration=Handling.Prepare<int,string>().On<ArgumentNullException>((ex,i)=>{// this handler will be invoked, but says to be ignored//return new HandlingResult<string>(false);//return Handling.Ignore<string>();returnfalse;}).On<ArgumentException>((ex,i)=>{varret=$"ArgumentException[ParamName={ex.ParamName}, InputParameter={i.Parameter}]";//return new HandlingResult<string>(true, ret);returnHandling.Handled(ret);}).On<Exception>((ex,i)=>{varret=$"Exception[InputParameter={i.Parameter}]";//return new HandlingResult<string>(true, ret);returnHandling.Handled(ret);});varresult=configuration.Catch(newArgumentNullException(nameof(param01)),987987);Console.WriteLine($"Handler[Handled={result.Handled}] -> '{result.Result}'");// Handler[Handled=True] -> 'ArgumentException[ParamName=param01, InputParameter=987987]'result=configuration.Catch(newArgumentOutOfRangeException(nameof(param01)),123123);Console.WriteLine($"Handler[Handled={result.Handled}] -> '{result.Result}'");// Handler[Handled=True] -> 'ArgumentException[ParamName=param01, InputParameter=123123]'result=configuration.Catch(newException(),54321);Console.WriteLine($"Handler[Handled={result.Handled}] -> '{result.Result}'");// Handler[Handled=True] -> 'Exception[InputParameter=54321]'}

Conditions

In this example, some handlers are conditionally invoked, even if the exception type match:

publicstaticvoidConditionalExceptionHandling(stringparam01,stringparam02,stringparam03){stringhandlerName=null;varconfiguration=Handling.Prepare().On<ArgumentNullException>(ex =>{handlerName="ArgumentNullException[ParamName=param01]";},(ex,i)=>ex.ParamName==nameof(param01)).On<ArgumentNullException>(ex =>{handlerName="ArgumentNullException[ParamName=param02]";},(ex,i)=>ex.ParamName==nameof(param02)).On<ArgumentNullException>(ex =>{handlerName=$"ArgumentNullException[ParamName={ex.ParamName}]";});varresult=configuration.Catch(newArgumentNullException(nameof(param01)));Console.WriteLine($"Handler[Handled={result.Handled}] -> '{handlerName}'");// Handler[Handled=True] -> 'ArgumentException[ParamName=param01]'result=configuration.Catch(newArgumentNullException(nameof(param03)));Console.WriteLine($"Handler[Handled={result.Handled}] -> '{handlerName}'");// Handler[Handled=True] -> 'ArgumentException[ParamName=param03]'}