如何保护Edit操作路线中的Asp.Net MVC 5不会引发未处理的异常？

Question

I have a standard Edit action in Asp.Net MVC 5 and I want to avoid throwing the unhandled exception when a get request is made without the id like ~/food/edit , so I did this.

    public ActionResult Edit(int id = 0)
    {
        if (id == 0)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }

        string result = _foodAppService.GetById(id);
        FoodVm food = string.IsNullOrEmpty(result) 
            ? null 
            : JsonConvert.DeserializeObject<FoodVm>(result);

        if (food == null)
        {
            return RedirectToAction("Index");
        }

        return View(food);
    }

My question is: Is it a good practice to handled it in this way or there are more suitable strategies ?

I'm new to this asking question thing, if a should I ask in another way, just let me know, thank you for your time.

Answer 1

In case zero could be valid its better to do

public ActionResult Edit(int? id)
{
    if (!id.HasValue)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
}

Answer 2

Or there can be more overall way to handle exceptions in MVC. You can use override of method OnException this gives you abbility to debug all exception in controllers in one method and handle them. Just add base class to all your controllers like this:

 public class BaseController : Controller
 {
    protected override void OnException(ExceptionContext filterContext)
    {
        string redirectUrl;
        var exception = filterContext.Exception;

        if (exception is EntityException)
        {
            redirectUrl = "/Content/error.html";
        }
        else
        {
            redirectUrl = "/Info/Index";
        }

        //do whatever you wont

        Response.Redirect(redirectUrl);
    }

Also use input parameters verification as Paul Swetz saied. This method is more genera, allows to intercept all exceptions, and don`t show errors to users.

Answer 3

Following @Fran 's advice. I built a action filter attribute called MissingParam

public class MissingParamAttribute : ActionFilterAttribute
{
   public string ParamName { get; set; }

   public override void OnActionExecuting(ActionExecutingContext filterContext)
   {
      if (filterContext.ActionParameters.ContainsKey(ParamName))
      {
         if (filterContext.ActionParameters[ParamName] == null)
         {
            filterContext.ActionParameters[ParamName] = 0;
         }
      }

   base.OnActionExecuting(filterContext);
  }
}

in the action I did this:

[MissingParam(ParamName="id")]
public ActionResult Edit(int id)

That way I don't need to mess with method parameter, any validating happens before. This implementation follows the Open/Close principle. I extended its functionality, but I didn't changed like the code in the question.

Answer 4

First and foremost its a good practice to use Try-Catch.

public ActionResult Edit(int id)
 {
     try
     {
            if (id != 0 || id!=null)
           {
            string result = _foodAppService.GetById(id);
            FoodVm food = string.IsNullOrEmpty(result) ? null:JsonConvert.DeserializeObject<FoodVm>(result);

            if (food == null)
            {
                return RedirectToAction("Index");
            }
            else
            {    
            return View(food);
            }
          }
         else
          {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
          }
    }
    catch (exception ex)
    {
    return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
}