ASP.NET Web Api：在ActionFilter / ModelState的错误响应中返回用户友好名称

Question

I'm using a view model with an ApiController that has Display(Name = "Friendly Name") attributes for each property. I've created a custom ActionFilterAttribute to validate the model state and return a bad request when the model is not valid. What I would like to do now is return custom JSON output that includes the user friendly names related to each model's properties. I can think of some hacky ways to do this but what's the preferred way?

Answer 1

EDIT: This will only be fixed in WebApi 5.1.

Have a look here - Web Api ModelState validation is ignoring the DisplayAttribute

---

Have a look at the official Microsoft documentation - ApiController.Validate .

You can achieve this by returning the ModelState in your response. eg

public class MyController : ApiController
    {
        public HttpResponseMessage Post(Product product)
        {
            if (ModelState.IsValid)
            {
                return new HttpResponseMessage(HttpStatusCode.OK);
            }
            else
            {
                return request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }
        }
    }

or if you want to do this through your ActionFilterAttribute you can use:

public class ValidateModelAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            if (actionContext.ModelState.IsValid == false)
            {
                actionContext.Response = actionContext.Request.CreateErrorResponse(
                    HttpStatusCode.BadRequest, actionContext.ModelState);
            }
        }
    }

This would return JSON like:

{ "Message": "The request is invalid.", "ModelState": { "product": [ "Required property 'Name' not found in JSON. Path '', line 1, position 17." ], "product.Name": [ "The Name field is required." ], "product.Weight": [ "The field Weight must be between 0 and 999." ] } }

Answer 2

In 'ActionFilterAttribute' you can can customize error message according your api requirement

public class ValidateModelAttribute : ActionFilterAttribute{
public override void OnActionExecuting(HttpActionContext actionContext)
{
    if (actionContext.ModelState.IsValid == false)
    {
        var error = new
        {
            status = false,
            message = "The request is invalid.",
            error = actionContext.ModelState.Values.SelectMany(e => e.Errors.Select(er => er.ErrorMessage))
        };
        actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.BadRequest, error);
    }
}}

{ "status": false, "message": "The request is invalid.", "error": [ "The First Name field is required.", "The Lname field is required.", "The Ename field is required." ], }