How to generate C# or TypeScript client code for OpenAPI (Swagger) specification

Nikolay Chebotov
Jun 2 · 4 min read

This How-To describes how to generate C# or TypeScript client code for OpenAPI (Swagger) specification with Unchase OpenAPI (Swagger) Connected Service to Visual Studio 2017/2019 projects.

The Unchase OpenAPI (Swagger) Connected Service is a Visual Studio 2017/2019 extension to generate C# (TypeScript) HttpClient (or C# Controllers) code for OpenAPI (formerly Swagger) web services with NSwag. Simply put, it is like kind old Add Service Reference for WCF or Add Web Reference for WSDL, but for JSON (YAML) API with customization of code generation like in NSwagStudio.

Follow 4 steps below to achieve this:

All steps of generation process in Visual Studio Community 2019 v16.1.3 with default options (without customization of code generation)

Step 1. Install the Connected Service

Launch the installed Visual Studio 2017/2019. Open the menu to manage Visual Studio extensions:

  • For Visual Studio 2017: Tools -> Extensions and Updates...
“Extensions and Updates…” menu item in Visual Studio Community 2017 v15.9.12
  • For Visual Studio 2019: Extensions -> Manage Extensions
“Manage Extensions” menu item in Visual Studio Community 2019 v16.1.3

Choose Online -> Visual Studio Marketplace tab. In search field type unchase, then install Unchase OpenAPI (Swagger) Connected Service (just click Download button):

Install Unchase OpenAPI (Swagger) Connected Service in Visual Studio

After all, restart the Visual Studio to install the Connected Service.

Step 2. Open the Connected Service wizard for Visual Studio project

Open the Visual Studio solution with project to generate client code in. In Solution Explorer make right-click on Connected Services or Dependencies item in the project for which you need to generate client code, and click on Add Connected Service:

“Connected Services” item in the project in Solution Explorer
“Dependencies” item in the project in Solution Explorer

Then choose Unchase OpenAPI (Swagger) Connected Service to show the Connected Service wizard:

Choose the Unchase OpenAPI (Swagger) Connected Service
“Unchase OpenAPI (Swagger) Connected Service” wizard

Step 3. Configure OpenAPI specification endpoint

In the first page of the wizard you need to configure some necessary options:

  • Service name — the name of the generated files prefix (by default, if field is empty — OpenAPIService);
  • OpenAPI (Swagger) specification URI (path) — the specification URI (URL or local file);
  • One or few of Generate CSharp Client, Generate TypeScript Client, Generate CSharp Controller — to generate C# (TypeScript) client code or/and C# Controllers code file(s) for OpenAPI specification. When you check a checkbox, the corresponding tab item with additional generation settings is added to the wizard:
Configure OpenAPI (Swagger) specification endpoint in the first page of the wizard

After setting the necessary options, you can immediately start generating the code files by clicking the Finish button. In this case, there will choose default code generation options.


There are a few optional options you can specify before start generation process:

  • In the Runtime and variables section — the same options as in NSwagStudio:
NSwagStudio “Runtime” and “Default Variables” options
  • Copy OpenAPI (Swagger) json-specification to nswag-file checkbox — the same as Create local Copy button in NSwagStudio:
NSwagStudio “Create local Copy” button
  • Open generated files on complete in IDE checkbox — allows automatically open the generated files in IDE in generation process;
  • If you need to set network credentials for connecting to the endpoint (specification file), you should specify options in the Network Credentials section. If your network used Proxy, you should specify options in the Web Proxy section:
Specify “Network credentials” and “Web Proxy with credentials” to access the specification file

Step 4 (Optional). Configure code generation options

If you want to specify some options for generating code, just need to go to generation settings tab(s):

All steps of generation process in Visual Studio Community 2019 v16.1.3 with customization of C# client code generation

There are the same options like in NSwagStudio.


Enjoy programming with Unchase!

Nikolay Chebotov

Written by

Security researcher, developer. Mostly working with “Centurion” and Visual Studio Extensions. https://github.com/unchase

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