I’m having a problem with .NET9.

In particular, this class represent the input of the endpoint where I am having the problem.

public class RequirementForAdd {
public string AttributeName { get; set; }
public RequirementOperator Operator { get; set; }
public string Value { get; set; }
public bool IsMustHave { get; set; }
}

In this class RequirementOperator is a simple Enum:

public enum RequirementOperator {
Equals,
GreaterThan,
LessThan,
GreaterThanOrEqual,
LessThanOrEqual,
}

I want that this Enum is accepted from the REST API as a string. Instead, even if I add the converter in this way:

// Add controllers services to the service collection, and configure JSON options.
builder.Services.AddControllers(options => {
       options.SuppressImplicitRequiredAttributeForNonNullableReferenceTypes =
       true;// Suppress implicit required attribute for non-nullable reference types.
       })
       .AddJsonOptions(options => {
       // Add JSON converter for enum strings and configure naming policy.
       options.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter());       
       });

The API turns out to accept an integer as you can see in the openapi file generated (with the new system that use MapOpenApi()) :

 "RequirementForAdd": {
        "type": "object",
        "properties": {
          "attributeName": {
            "type": "string",
            "nullable": true
          },
          "operator": {
            "$ref": "#/components/schemas/RequirementOperator"
          },
          "value": {
            "type": "string",
            "nullable": true
          },
          "isMustHave": {
            "type": "boolean"
          }
        }
      },
      "RequirementOperator": {
        "type": "integer"
      },

I’m pretty sure that when I used .NET 8 it worked effortless and the API accepted strings for the enums.

Someone can support me and tell me how can I do to obtain that RequirementOperator is a string?

Thanks!