NJsonSchema for .NET

JSON Schema draft v4 reader, generator and validator for .NET

NuGet packages:

• NJsonSchema: JSON Schema 4 validation and parsing classes
• NJsonSchema.CodeGeneration: Classes to generate code from a JSON Schema 4 (C# and TypeScript)

The library uses Json.NET to read and write JSON data.

Features:

• Read existing JSON Schemas and validate JSON data
• Generate JSON Schema from .NET type via reflection (with support for many attributes/annotations)
• Support for schema references ($ref) (relative, URL and file)
• Generate C# and TypeScript code from JSON Schema

NJsonSchema is heavily used in NSwag, a Swagger API toolchain for .NET which generates client code for Web API services.

NJsonSchema usage

The JsonSchema4 class can be used as follows:

varschema=JsonSchema4.FromType<Person>();varschemaData=schema.ToJson();varerrors=schema.Validate("{...}");foreach(varerrorinerrors)Console.WriteLine(error.Path+": "+error.Kind);schema=JsonSchema4.FromJson(schemaData);

The Person class:

publicclassPerson{[Required]publicstringFirstName{get;set;}[Required]publicstringLastName{get;set;}publicGenderGender{get;set;}[Range(2,5)]publicintNumberWithRange{get;set;}publicDateTimeBirthday{get;set;}publicCompanyCompany{get;set;}publicCollection<Car>Cars{get;set;}}publicenumGender{Male,Female}publicclassCar{publicstringName{get;set;}publicCompanyManufacturer{get;set;}}publicclassCompany{publicstringName{get;set;}}

The generated JSON schema data stored in the schemaData variable:

{
"$schema": "http://json-schema.org/draft-04/schema#",
"typeName": "Person",
"type": "object",
"required": [
"FirstName",
"LastName",
"Gender",
"NumberWithRange",
"Birthday"
],
"properties": {
"FirstName": {
"type": "string"
},
"LastName": {
"type": "string"
},
"Gender": {
"type": "string",
"enum": [
"Male",
"Female"
]
},
"NumberWithRange": {
"type": "integer",
"maximum": 5.0,
"minimum": 2.0
},
"Birthday": {
"type": "string",
"format": "date-time"
},
"Company": {
"typeName": "Company",
"type": "object",
"properties": {
"Name": {
"type": "string"
}
}
},
"Cars": {
"items": {
"typeName": "Car",
"type": "object",
"properties": {
"Name": {
"type": "string"
},
"Manufacturer": {
"typeName": "Company",
"type": "object",
"$ref": "#/properties/Company"
}
}
},
"type": "array"
}
}
}

NJsonSchema.CodeGeneration usage

The NJsonSchema.CodeGeneration can be used to generate C# or TypeScript code from a JSON schema:

vargenerator new CSharpClassGenerator(schema);varfile=generator.GenerateFile();

The file variable now contains the C# code for all the classes defined in the JSON schema.

Final notes

Applications which use the library:

• VisualJsonEditor, a JSON schema based file editor for Windows.
• NSwag: The Swagger API toolchain for .NET