[BUG][CSharp] Bug generating code with Enum having maxLength property

Hi

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

We have an open api spec version 2.0 and we are trying to generate code in csharp .
We have an issue in generated SDKif the property whose type is string is an enum and has maxLength specified . Please refer line 121 in attached contract .
petstore.txt

Below is the code in csharp and the one in bold throws error.

// Status (string) maxLength
if(this.Status != null && this.Status.Length > 20)
{
yield return new System.ComponentModel.DataAnnotations.ValidationResult("Invalid value for Status , length must be less than 20.", new [] { "Status " });
}

openapi-generator version

3.3.4

OpenAPI declaration file content or url

petstore.txt

Command line used for generation

Steps to reproduce

Related issues/PRs

Suggest a fix

csharp code should be like The code should be like this.Status.ToString().Length.

In the snapshot below we can make fix

Start with the attached petstore.txt OpenAPI 2.0 specification and reproduce generation for C#. Inspect the generated validation for the enum string property with maxLength 20, then verify the output compiles and handles the length check without treating the enum as a direct string.