How to generate C# API from the swagger.json OpenAPI definition

Using Visual Studio 2022

The easiest solution is just to add a connected service to the project:

and then configure the API code creation:

When choosing Finish, the code is created as .\obj\swaggerClient.cs.

The only problem with the created code is that nullable object references in the OpenAPI description are not created as nullable in the C# code:

"timeseriesResource": {
            "allOf": [
              {
                "$ref": "#/components/schemas/MeshTimeseriesResource"
              }
            ],
            "description": "Path to the time series in the Resources definition.",
            "nullable": true
          },

is converted to:

/// <summary>
/// Path to the time series in the Resources definition.
/// </summary>
[Newtonsoft.Json.JsonProperty("timeseriesResource", Required = Newtonsoft.Json.Required.Default, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
public MeshTimeseriesResource TimeseriesResource { get; set; }

which is not correct.

Make it right using the NSwagStudio

The utility may be downloaded from here.

Configure a NSwagStudio project

Do the following steps:

1. Specify input:
2. Select which runtime to use (e.g. Net70).
3. In the OpenAPI/Swagger Specification folder, enter the URL to the Mesh Rest API (e.g. http://localhost:7060/swagger/v1/swagger.json).

1. Specify outputs:
2. Select CSharp Client and select the CSharp Client page.

3. Enter relevant text into the following attributes:

   • Namespace (same as the project the code is added to, f.ex. MeshRestAPI.Test).
   • Class Name (f.ex. MeshRestAPI).
   • Select the Generate Nullable Reference Type (NRT) annotations (C# 8) option.
   • Output file path (f.ex. C:\Dev\energy-mesh-rest-api\src\MestRestAPI.Test\MeshRestAPI.cs).

   

4. Generate the code by choosing Generate Files in the lower right corner.

5. Save the configuration using the File\Save options to a file in your project (e.g. C:\Dev\energy-mesh-rest-api\src\MestRestAPI.Test\MeshRestAPI.nswag).

You are then ready to use the API from your code.