ModelState.Isvalid invalidating field even though default value existed - validation

Question

public abstract class Base : IBase
{
[Required]
public int key {get;set;}
}
public class Entity: Base
{
public string Name {get;set;}
}
public class child : Entity
{
[Required]
public string Park {get;set;}
}
ActionFilter
public class ValidateViewModelAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext actionContext)
{
if (actionContext.ModelState.IsValid == false) {
actionContext.Response = actionContext.Request.CreateErrorResponse(HttpStatusCode.BadRequest, actionContext.ModelState);
}
}
}
Now, when value is posted to API then, not setting "Key" field as it is the request for SAVE. Problem is, above attribute says, MODEL IS INVALID for field "key" . Its already there as 0 value for Id field (as default int).
I expect, it should validate true as 0 is default value.
NOTE: I could not remove or make any change in BASEENTITY and PARENT entity above.
I have only control in CHILD entity and this attribute class.

Answer 1

To ignore a property that is marked as [Required] you can use ModelState.Remove("propertyName");
Also, your property has a value of 0 because an int cannot have a value of NULL so the 0 is automatically attributed. But if you did not pass this value in the form data, the model validation will "consider" that it is NULL and thus will make the model invalid. If you do not want to use the call to Remove as shown above, you will have to explicitly give a value to the Key property :-)
source: The first comment on this page - credit for this explanation #Stephen Muecke
Use something like
public class ValidateViewModelAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext actionContext)
{
ModelState.Remove("key");
if (actionContext.ModelState.IsValid == false) {
actionContext.Response = actionContext.Request.CreateErrorResponse(HttpStatusCode.BadRequest, actionContext.ModelState);
}
}
}
Note: By default, MVC6 model validation will simplicity tag all non-nullable value types as required (god knows why).
call
DataAnnotationsModelValidatorProvider.AddImplicitRequiredAttributeForValueTypes = false;
disable this behaviour.

Answer 2

I have the same problem and solved it by this way :
[AcceptVerbs("Post")]
public ActionResult EditingInline_Create([DataSourceRequest] DataSourceRequest request, Model.Server server)
{
if (server != null && ModelState.IsValid) //Invalid!!
{
_exchangeService.Create(server);
}
return Json(new[] { server }.ToDataSourceResult(request, ModelState));
}
and replace model with viewModel ,because in viewModel we don`t have ID (refer to Use ViewModel)
then we will have :
[AcceptVerbs("Post")]
public ActionResult EditingInline_Create([DataSourceRequest] DataSourceRequest request, ViewModel.ServerViewModel server)
{
if (server != null && ModelState.IsValid)
{
_exchangeService.Create(server);
}
return Json(new[] { server }.ToDataSourceResult(request, ModelState));
}