T4 template to generate TypeScript interface definitions.
C# TypeScript
Latest commit 75f4003 Jul 29, 2016 @cskeppstedt committed on GitHub Add note on project inactivity


T4TS (not worked on)

This project is inactive

I am no longer working on this project. Since it's been a long while since I was active on the .NET platform, I am unable to keep up with new versions of .NET to maintain the project. Thanks to all that have been contributing, it's been fun!

Build status

Build status


  1. Install the NuGet package (https://nuget.org/packages/T4TS).

  2. Decoreate any C# class that you want to generate an interface for, with the TypeScriptInterfaceAttribute (in the T4TS namespace).

  3. Run the T4TS.tt-file (right-click and select Run custom tool).

  4. The generated file T4TS.d.ts will now contain the interfaces that can be used in your TypeScript files.


C# classes:

public class MyModel
    public int Number { get; set; }
    public string Name { get; set; }
    public ReferencedModel Ref { get; set; }

public class ReferencedModel
    public double Fraction { get; set; }
    public int[] Digits { get; set; }

Resulting T4TS.d.ts:

module T4TS {
    export interface MyModel {
        Number: number;
        Name: string;
        Ref: ReferencedModel;
    export interface ReferencedModel {
        Fraction: number;
        Digits: number[];

This interface can now be used in your TypeScript files:

/// <reference path="T4TS.d.ts" />
class Test {
    constructor () {
        // Make an AJAX post and get some data from the server.
        // In the callback, you can specify that the data is of a certain type:
        $.post('./example', {}, (data: T4TS.MyModel) => {
            // Intellisense support for the properties:


  • Only public properties are considered

  • Right now, System.DateTime is considered a string in the type translation. The main reason is that the JSON serialization in .NET MVC will typically serialize a DateTime as "\/Date(ticks)\/"

  • The type translation works like this, from C# => TypeScript, for each property:

    • Built-in numeric type (int, double, float, etc.) => number
    • string => string
    • Nullable<T> => T?
    • A class marked with [TypeScriptInterface] => lookup the generated TypeScript name
    • Otherwise => any
    • For IEnumerable<T>, Collection<T>, List<T>, IList<T> and T[] => lookup type for T as above, and return T[].
  • Inheritance of interfaces is supported. If Bar inherits Foo in C# and both are marked with the TypeScriptInterfaceAttribute, the generated interface would be interface Bar extends Foo {....

Customize the generated interfaces

The attribute TypeScriptInterfaceAttribute is set on C# classes, and has the following properties:

  • Name: Specifies the name of the interface (default is the class name).
  • Module: Specifies the module of the interface (default T4TS).
  • NamePrefix: If specified, the interface name will be prefixed with this string.

The attribute TypeScriptMemberAttribute can be set on the properties of a C# class, and has the following properties:

  • Name: Specifies the name of the member (default is the property name).
  • Optional: Specifies whether this member should be optional, ie. member?: type instead of member: type.
  • Type: Specifies the type of the member (default is to do type translation of the property).
  • CamelCase: If set to true, the first character of the member name will be lower cased.
  • Ignore: If set to true, the property will be ignored.

Default settings

There are a couple of default settings that can be specified in the T4TS.tt.settings.t4 file.

  • DefaultModule: The default module name of an interfaces (if not specified by TypeScriptInterfaceAttribute). Default is "T4TS".
  • DefaultOptional: The default value for the Optional flag for TypeScriptMemberAttribute. Default is false.
  • DefaultCamelCaseMemberNames: The default value for the CamelCase flag for TypeScriptMemberAttribute. Default is false.
  • DefaultInterfaceNamePrefix: The default value for the NamePrefix flag for TypeScriptInterfaceAttribute. Default is "".
  • CompatibilityVersion: The version of Typescript that is targeted. This will help handling breaking changes in the language grammar and/or compiler. Default (right now) is

Known problems

TextTransformation fails:

I have experienced some error message the first time the T4TS package is installed via NuGet. However, if you build the project, or run the .tt-file, the error message disappears.


See README.md in T4TS.Build and T4TS.Build.Builder for details.


Apache License, Version 2.0

Thanks to T4MVC, which has been the inspiration. I also learned how to use the .tt-stuff from reading the source, and using part of the source code from T4MVC.