Creating Custom Action Filters in ASP.NET MVC

I recently had a need to create a custom Action Filter in ASP.NET MVC to perform some pre-processing before I executed my Controller Action Methods.

I followed these MSDN articles to get started creating my Custom Action Filter:

https://msdn.microsoft.com/en-us/library/dd381609%28v=vs.100%29.aspx

https://msdn.microsoft.com/en-us/library/dd410056%28v=vs.100%29.aspx

However, there was not a great deal of insight on how to pass values and use values in my ActionFilter as well as how to create a custom ViewResult (such as by adding errors to the ModelState Errors collection).

Therefore, I played around with some code until I was finally able to get this code sample working:

namespace MvcFilters

{

    public class CustomFilterAttribute : ActionFilterAttribute

    {

        public string ModuleName { get; set; }

        public override void OnActionExecuting(ActionExecutingContext filterContext)

        {

            bool myValue = true;

            if (myValue)

            {

                base.OnActionExecuting(filterContext);

            }//if

            else

            {

                filterContext.Result = new CustomResult(this.ModuleName);

            }

        }

        public override void OnActionExecuted(ActionExecutedContext filterContext)

        {

            base.OnActionExecuted(filterContext);

        }

    }

}

namespace MvcFilters

{

    public class CustomResult : ViewResult

    {

        public CustomResult(string moduleName)

        {

            string strErrorMessage = string.Format("{0} cannot be used", moduleName);

            this.ViewData.ModelState.AddModelError("", strErrorMessage);

        }

        public override void ExecuteResult(ControllerContext context)

        {

            base.ExecuteResult(context);

        }

    }

}

Then, in order to use my ActionFilterAttribute in my ASP.NET MVC Controller, I simply decorate my ActionMethod in the following manner:

[HttpGet]

[CustomFilter(ModuleName ="Module1")]

public ActionResult Module1()

{

   return View();

}

 

That was all that was needed to get my Custom ASP.NET MVC ActionFilter to work and return my ModelState Error messages!!