Cannot pass TempData Value from ExceptionFilter

Question

.Net Core 3.1

I have an ExceptionFilter, where I'd like to pass TempData value with a RedirectResult.

Here is my Code below:

public class CustomExceptionFilterAttribute : IExceptionFilter
{
    private readonly ITempDataProvider _tempDataProvider;

    public CustomExceptionFilterAttribute(ITempDataProvider tempDataProvider)
    {
         _tempDataProvider = tempDataProvider;
    }

    public void OnException(ExceptionContext context)
    {
        //Log The Exception here

        //After Log
        var url = context.HttpContext.Request.Path.ToUriComponent();
        context.ExceptionHandled = true;
        context.HttpContext.Response.Clear();

        var tempData = new TempDataDictionary(context.HttpContext, _tempDataProvider);
        tempData.Add("UserFriendlyMessage", "An Error Occured! Please contact Admin!");
        tempData.Keep("UserFriendlyMessage"); //This didn't work either...

        var result = new RedirectResult(url);
        context.Result = result;    
    }
}

[TypeFilter(typeof(CustomExceptionFilterAttribute))]
public class MyController : Controller
{...

public IActionResult MyAction()
{
    return View();
}
[HttpPost]
public IActionResult MyAction(MyModel model)
{
    try
    { 
       int a = 5;
       int b = a / 0;
    }
    catch(Exception ex)
    {

    }
    return View();
}

So as you see above, my aim is to Redirect the user to the same page(where exception occurs) and prevent them to redirect a 500StatusCode Error Page.

Actually this code redirects user the way I want to, but just TempData value is not passing.

I have tried:
- context.HttpContext.Response.Clear(); Tried this code and without this code.
- tempData.Keep("UserFriendlyMessage"); Tried this code and without this code.

Answer 1

I've figured it out, I hope it will help somebody who face with this situation.

I've deleted ITempDataProvider and put ITempDataDictionaryFactory instead.

public class CustomExceptionFilterAttribute : IExceptionFilter
{
    private readonly ITempDataDictionaryFactory _tempDataFactory;

    public CustomExceptionFilterAttribute(ITempDataDictionaryFactory tempDataFactory)
    {
         _tempDataFactory = tempDataFactory;
    }

    public void OnException(ExceptionContext context)
    {
        //Log The Exception here

        //After Log
        var url = context.HttpContext.Request.Path.ToUriComponent();
        context.ExceptionHandled = true;
        context.HttpContext.Response.Clear();

        //-----------THIS WAS THE PART THAT HAS PROBLEM----------------
        //var tempData = new TempDataDictionary(context.HttpContext, _tempDataProvider);
        //tempData.Add("UserFriendlyMessage", "An Error Occured! Please contact Admin!");
        //tempData.Keep("UserFriendlyMessage"); //This didn't work either...
        //var result = new RedirectResult(url);
        //context.Result = result; 
        //-------------------------------------------------------------   

        //I've changed it to:
        var tempData = _tempDataDictionaryFactory.GetTempData(context.HttpContext);
        tempData.Add("UserFriendlyMessage", "An Error Occured!"); 

        var result = new RedirectResult(url);
        context.Result = result;
    }
}

NOTE: So I think the wrong part was that I was creating a new instance of TempData with new TempDataDictionary, and now I'm taking the current TempData,
still if someone has a knowledge of what was I doing wrong, please tell me. :)