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Visual Studio–Generate C# client for OpenAPI

There are multiple ways to generate a C# client based on an OpenAPI specification file. Today I want to show you how this can be done directly inside Visual Studio.

To import an OpenAPI reference, you can right-click on your project and choose Add –> Service Reference:

Choose OpenAPI from the list of possible service references and click on Next:

Now we can specify the details to our OpenAPI JSON file. Click on Finish to generate the client:

It can take some time to generate the client. So be patient.

What is happening behind the scenes?

Let us have a look at all the things that Visual Studio is doing behind the scenes.

First a copy of the OpenAPI json file is imported into our project and stored inside an OpenAPIs folder:

On this JSON file the build action is set to Open API File Reference and specific code generation attributes are configured:

Our updated csproj file looks like this:

Behind the scenes the code generator is using the Microsoft.dotnet-openapi command line tool which uses NSwag in the end.

We can further control what is generated by specifying additional options:

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