[BUG] Exception Thrown for Missing Non-Required Query Parameters in C# Generated Code

I am encountering an issue where the C# server code generated by OpenAPI Generator (version 7.1.0) throws exceptions when non-required query parameters are absent in a request. This problem arises despite these parameters not being marked as required in my OpenAPI document, which I created using Stoplight Studio (version 2.10.0).

Steps to Reproduce:

1. OpenAPI Document Creation:

   • Using Stoplight Studio 2.10.0, I created an OpenAPI document. In this document, I have several query parameters not marked as required.
   • Example snippet from the YAML file:

     parameters:
        - schema:
            type: string
            nullable: true
          in: query
          name: data
          description: 'For more information, refer to ....'
          allowEmptyValue: true
     

   • Stoplight Studio does not set these parameters as nullable, I have added nullable manually..

2. OpenAPI Generator Usage:

   • I used the OpenAPI Generator CLI (version 7.1.0) with the following command to generate the C# server code:

     openapi-generator-cli generate -i [path-to-myDoc.yaml] -g aspnetcore -o [output-directory] --additional-properties=aspnetCoreVersion=6.0,buildTarget=library,packageName=MyRestSvr,operationIsAsync=true,operationResultTask=true
     

3. Encountered Issue:

   • In the generated C# server code, the absence of these query parameters (which are not required as per the OpenAPI document) leads to exceptions.

Workaround Implemented:

• I manually modified the generated code to define these query parameters as nullable in C#. This resolved the issue.

Expected Behaviour:

• The generated code should handle non-required query parameters without throwing exceptions when they are missing.

Start by reproducing the issue with the provided YAML parameter definition and the OpenAPI Generator CLI command targeting aspnetcore. Inspect the generated C# handling for absent optional query parameters and verify that generated server code accepts them without throwing exceptions.