Generally, whenever something is to be saved to the database or to any other place, as a best practice almost everyone use to validate the state of the model. So, if state of model is valid, we proceed and if model state is invalid, we handle it as a bad request. This looks something like this: If(!ModelState.IsValid) { // create bad request object } So, all these were done by using the IsValid property. Problem Now what if we have to perform the same validation for all the models. Are we going to write the same validation in each and every controller? Of course, No. Solution Rather than duplicating the same code in each and every controller, we can create a global filter. This global filter has few methods, but for our purpose we can go with OnActionExecuting . public class ValidateModelStateFilter : ActionFilterAttribute { public override void OnActionExecuting(ActionExecutingContext context) { if (!context.ModelState.Is...