Brtdku

I am trying to figure out how to wire up exception handling in an ASP.NET Core Razor pages site to allow the user to stay on the same page when an exception occurs with a friendly error message.

Once the user submits the form on the Edit view, call the back end middle-tier to persist the data if they have the proper permissions. If they don't have proper permissions, a custom validation exception is thrown from the middle-tier.

   private readonly IToolsService m_oToolsService;



   public EditModel(IToolsService toolsService)

   {

        m_oToolsService = oToolsService;

   }



   public async Task<IActionResult> OnGetAsync()

   {

        var vm = olsService.GetData():



        // Wire up UI with the ViewModel

        return Page();

   }



    public async Task<IActionResult> OnPostEditAsync(ViewModel vm)

    {

        if (false == ModelState.IsValid)

        {

            return Page();

        }



        m_oToolsService.SaveData(vm);

    }

If the call to "m_oToolsService.SaveData(vm);" fails, I'd like to keep the user on the same page with a friendly error message (and with the form data that they tried to post).

I could wrap the OnPost/OnGet ActionMethods with try/catch blocks, however, that gets redundant in all of the PageModels and bloats the code.

I have tried adding custom exception handling Middleware, and while that will catch the custom error, it redirects the user to an error page.

I have also added a custom exception filter similar to the example below but that isn't keeping the user on the page either.

public class CustomExceptionFilterAttribute : ExceptionFilterAttribute

{

    private readonly IHostingEnvironment _hostingEnvironment;

    private readonly IModelMetadataProvider _modelMetadataProvider;

    private readonly ITempDataDictionaryFactory _tempDataDictionaryFactory;



    public CustomExceptionFilterAttribute(IHostingEnvironment hostingEnvironment, ITempDataDictionaryFactory tempDataDictionaryFactory, IModelMetadataProvider modelMetadataProvider)

    {

        _hostingEnvironment = hostingEnvironment;

        _modelMetadataProvider = modelMetadataProvider;

        _tempDataDictionaryFactory = tempDataDictionaryFactory;

    }



    public override void OnException(ExceptionContext context)

    {

        if (!_hostingEnvironment.IsDevelopment())

        {

            // do nothing

            return;

        }



        var tempData = _tempDataDictionaryFactory.GetTempData(context.HttpContext);



        var result = new ViewResult

        {

            ViewName = "/Edit",

        };



        context.ExceptionHandled = true; // mark exception as handled

        HttpResponse response = context.HttpContext.Response;

        context.Result = result;

  }

No matter what I research, everything seems to point back to using the .NET Core Middleware to redirect to a specific error page. Does anyone have any ideas on how to handle exceptions but keep the user on the same view?