[BUG] [csharp] ToString() on OneOf produces string with class description artifact

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When you use schema oneOf on the in path parameter (and maybe response as well) the resulting object's ToString method that is used to generate the full URL produces artifacts like so:

stringBuilder.Append("class IntOrString{\n");
      stringBuilder.Append("  ActualInstance: ").Append(this.ActualInstance).Append("\n");
      stringBuilder.Append("}\n");

openapi-generator version

7.0.1

OpenAPI declaration file content or url

Generation Details

Relevant part of my csharp.json file:

  "generatorName": "csharp",
  "targetFramework": "net7.0",

openapi-generator-cli generate -i openapi.json -o client -c csharp.json

Steps to reproduce

Executing code to fetch Resource using the apiInstance

int value = 777777;

            try
            {
                // GET resource by int
                Resource result = apiInstance.GetResourceByIntOrString(new IntOrString(value));
            catch (ApiException e)
            {
                _logger.LogInformation("Exception when calling DefaultApi.GetResource: " + e.Message );
                _logger.LogInformation("Status Code: "+ e.ErrorCode);
                _logger.LogInformation(e.StackTrace);
            }

fails with:

Related issues/PRs

Suggest a fix

Make ToString() method return only the content of ActualInstance.

Generate the C# client with the supplied csharp.json settings and reproduce the request using the IntOrString path parameter. Start by locating the generated OneOf model's ToString() implementation and compare its output with the URL construction. Done means ToString() contributes only the ActualInstance content, without the class-description artifact.