/NJsonSchema

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

Primary LanguageC#Microsoft Public LicenseMS-PL

NJsonSchema for .NET

Build status NuGet Version

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

NuGet packages:

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
  • Support for schema references ($ref)
  • 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 type can be used as follows:

var schema = JsonSchema4.FromType<Person>();
var schemaData = schema.ToJson();

var jsonToken = JToken.Parse("...");
var errors = schema.Validate(jsonToken);

foreach (var error in errors)
    Console.WriteLine(error.Path + ": " + error.Kind);

schema = JsonSchema4.FromJson(schemaData);

The Person class:

public class Person
{
    [Required]
    public string FirstName { get; set; }

    [Required]
    public string LastName { get; set; }

    public Gender Gender { get; set; }

    [Range(2, 5)]
    public int NumberWithRange { get; set; }

    public DateTime Birthday { get; set; }

    public Company Company { get; set; }

    public Collection<Car> Cars { get; set; }
}

public enum Gender
{
    Male,
    Female
}

public class Car
{
    public string Name { get; set; }

    public Company Manufacturer { get; set; }
}

public class Company
{
    public string Name { 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:

var generator new CSharpClassGenerator(schema);
var file = 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