[C#] Bug generating client with application/x-www-form-urlencoded request body

Description

Client SDK codegen generates an invalid C# ApiXXXX object that doesn't compile when the request body is configured to be application/x-www-form-urlencoded. The generated XXXXPostWithHttpInfo method does not contain arguments that are referenced within the method.

Swagger-codegen version

Version: SwaggerHub portal

Swagger declaration file content or url

Here is a sample endpoint, this is based off an example from the docs

openapi: 3.0.0
info:
  version: 1.0.0
  title: Bug Example
paths:
  /example:
    post:
      requestBody:
        required: true
        content:
          application/x-www-form-urlencoded:
            schema:
              type: object
              properties:
                name:          # <!--- form field name
                  type: string
                fav_number:    # <!--- form field name
                  type: integer
              required:
                - name
                - email
      responses:
        '200':
          description: OK

It generates the following output, which does not compile, due to the request body parameters not being generated:

public ApiResponse<Object> ExamplePostWithHttpInfo ()
{
    // omitted

    // name and favNumber are not declared
    if (name != null) localVarFormParams.Add("name", this.Configuration.ApiClient.ParameterToString(name)); // form parameter
    if (favNumber != null) localVarFormParams.Add("fav_number", this.Configuration.ApiClient.ParameterToString(favNumber)); // form parameter

    // omitted
}

Command line used for generation

This was generated using the SwaggerHub Export menu

Steps to reproduce

The following SwaggerHub codegen options were used:

• .NET 1.3 Standard Compatible
• netCoreProjectFile
• Custom package name

Related issues/PRs

This seems to be related to the issue reported at #8346 but this is different in that it is for application/x-www-form-urlencoded and C# instead of multipart/form-data and Java.

Start by generating the C# client from the supplied OpenAPI 3.0 example with the listed SwaggerHub options, then inspect the generated ApiXXXX object's XXXXPostWithHttpInfo method. Compare its form-parameter references with the method arguments; done means the generated client compiles without undeclared name or favNumber references.