How can I support GET routes for both GUID and integer? I realize GUIDs are not ideal, but it is what it is for now. I'm wanting to add support for integers to make it easier for users to remember and communicate what should be unique "keys."

Example routes:

testcases/9D9A691A-AE95-45A4-A423-08DD1A69D0D1   
testcases/1234

My WebApiConfig:

public static void Register(HttpConfiguration config)
{
    config.MapHttpAttributeRoutes();
    var routes = config.Routes;

    routes.MapHttpRoute("DefaultApiWithAction", 
        "Api/{controller}/{action}");

    routes.MapHttpRoute("DefaultApiWithKey",
        "Api/{controller}/{key}",
        new { action = "Get" },
        new { httpMethod = new HttpMethodConstraint(HttpMethod.Get), key = @"^\d+$" });

    routes.MapHttpRoute("DefaultApiWithId", 
        "Api/{controller}/{id}", 
        new { action = "Get" }, 
        new { httpMethod = new HttpMethodConstraint(HttpMethod.Get) });

    routes.MapHttpRoute("DefaultApiGet", 
        "Api/{controller}", 
        new { action = "Get" }, 
        new { httpMethod = new HttpMethodConstraint(HttpMethod.Get) });

    routes.MapHttpRoute("DefaultApiPost", 
        "Api/{controller}", 
        new { action = "Post" }, 
        new { httpMethod = new HttpMethodConstraint(HttpMethod.Post) });
}

My controller (method signatures only):

[RoutePrefix("Api/TestCases")]
public class TestCasesController : PlanControllerBase
{
    [Route("")]
    public OperationResult<IEnumerable<TestCaseDTO>> Get([FromUri] TestCaseRequest request)

    [Route("{id}")]
    [HttpGet]
    public OperationResult<TestCaseDTO> Get(Guid id)

    [Route("{key}")]
    [HttpGet]
    public OperationResult<TestCaseDTO> Get(int key)

    ...
}

I'm getting an Internal Server Error when I attempt to call the resource using the integer. Any help is appreciated!