Globally ModelState Validation In Asp.Net Core Mvc - asp.net-core

Question

How to Can I create a custom Action Filter which will check if the ModelState is valid, and if not, it returns ModelState Errors To the Same View ?
I want to write a Custom Action Filter, which, Before all POST requests, Ensure that ModelState is valid and if ModelState is not valid,it will return the ModelState Errors to the same View.
This is my sample code. But I really don't know how to return ModelState Errors to the same view.
namespace Site.Web.Infrastructures.CustomValidationAttribute
{
public class GlobalMvcValidateModelStateAttribute : ActionFilterAttribute
{
public override Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
{
if (!context.ModelState.IsValid)
{
List<string> list = (from modelState in context.ModelState.Values from error in modelState.Errors select error.ErrorMessage).ToList();
//Also add exceptions.
list.AddRange(from modelState in context.ModelState.Values from error in modelState.Errors select error.Exception.ToString());
context.Result = new BadRequestObjectResult(list);
}
return base.OnActionExecutionAsync(context, next);
}
}
}

Answer 1

Here's what you need to add global ModelState validation for Views :
public class GlobalModelStateValidatorAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext context)
{
if (!context.ModelState.IsValid)
{
Controller controller = context.Controller as Controller;
object model = context.ActionArguments.Any()
? context.ActionArguments.First().Value
: null;
context.Result = (IActionResult)controller?.View(model)
?? new BadRequestResult();
}
base.OnActionExecuting(context);
}
}
Then you need to register this Filter in your application:
services.AddMvc(opt =>
{
opt.Filters.Add(typeof(GlobalModelStateValidatorAttribute));
});
And here's the code sample: https://github.com/MoienTajik/AspNetCoreGlobalModelStateValidator