Asp.Net Core Razor display an error message from if...else

Question

I have a button triggering OnPost action "PTWIssue" asp-route-idPTWNo= "@Model.PTWNo" type= "submit" class = "btn btn-link text-info font-weight-bolder mt-2 mb-2" style= "font-size:20px;" data-toggle= "tooltip" data-placement= "top" title= "Issue the Permit to Work and send to Receiver" >Issue Permit To Work On OnPost I have a check for string. I want to verify that there is no status "Awaiting" and then continue with OnPost. If the check fail, I want a simple message "Error on check" and the process to not continue. I have the following var checkIsoCert = await (from a in _context.IsoCerts.Where(s => s.PTWNo == idPTWNo) join b in _context.IsoDetails on a.IdIC equals b.IdIC into TempData1 from c in TempData1 select new { c.IsStatus }).ToListAsync(); string myString = "Awaiting" ; var matchingvalues = checkIsoCert.Where(x => x.IsStatus.Equals(myString)); if (matchingvalues == null ) { var ptwStatus = _context.PTWContents.First(s => s.PTWNo == idPTWNo); ptwStatus.PTWStatus = "Issued" ; await _context.SaveChangesAsync(); return RedirectToPage( "PTWForm" , "PTWNoId" , new { ptwNoId = idPTWNo }); } else { //show an error message such as -You have not complete IsoCert- } What I need is to display the message on error. How do I do that on Razor pages?

Sachin Singh · Answer

don't use script use bootstrap alert , it looks good. Also in your method , don't use int to store data , other wise it will never be null , by default int has 0 when it has nothing , if you can't use string then use nullable "int ?" @ if (Model.Error==0) { class = "alert alert-danger" role= "alert" > This is a danger alert—check it out ! }

Sachin Singh · Answer

simply use viewbag sir if (matchingvalues == null ) { var ptwStatus = _context.PTWContents.First(s => s.PTWNo == idPTWNo); ptwStatus.PTWStatus = "Issued" ; await _context.SaveChangesAsync(); return RedirectToPage( "PTWForm" , "PTWNoId" , new { ptwNoId = idPTWNo }); } else { ViewBag.ErrorMessage= "You havn't completed IsoCert" ; } // in Razor page @ViewBag.ErrorMessage

Marius Vasile · Answer

Forget about old school, I will have the error message displayed at the top of the page, it looks better than popup. Thank you Sachin

Sachin Singh · Answer

in page model create one more property like public string Error {get;set;} set it on method and use it like normal model property in razor.

Sachin Singh · Answer

also test with viewdata , it should work ViewData["MyString"] = "Error Message"; // in Page model @ViewData["MyString"] // in razor

Sachin Singh · Answer

check this https://www.learnrazorpages.com/razor-pages/viewdata

Yogeshkumar Hadiya · Answer

You can return view in else part with a new variable or model property then check in your razor page if that property has value which you pass from here then show error message like below . @if( MyVar =="error") { b > This is your error message b > }

Marius Vasile · Answer

It works as alert, highlighting the error, agree, but I am old school, I would like to have it as a popup and for some reasons, jquery modal popup is not working on if else

Marius Vasile · Answer

I have a pop up with @ if (Model.Error == null ) { "text/javascript" > var message = "Not all Isolation steps are implemented" ; if (message) alert(message); } but it doesn't look too good. any other ideeas?

Marius Vasile · Answer

OK, got it figuered out by int error = PTWIsoDetails.Count(x => x.IsStatus.Equals(myString)); Error = error.ToString(); and @ if (Model.Error == null ) { This is an error } but now I think a popup twill look better to show the message, most probably a jquery

Marius Vasile · Answer

Ok, the error is not related to the message, was different source and fixed. However, I still can't show the message

Marius Vasile · Answer

When I use string myString = "Awaiting" ; var matchingvalues = checkIsoCert.Where(x => x.IsStatus.Equals(myString)); if (matchingvalues == null ) { var ptwStatus = _context.PTWContents.First(s => s.PTWNo == idPTWNo); ptwStatus.PTWStatus = "Issued" ; await _context.SaveChangesAsync(); return RedirectToPage( "PTWForm" , "PTWNoId" , new { ptwNoId = idPTWNo }); } else { ViewData[ "MyString" ] = "You havn't completed IsoCert" ; } return Page(); and class = "col-12 d-flex justify-content-center" > "PTWIssue" asp-route-idPTWNo= "@Model.PTWNo" type= "submit" class = "btn btn-link text-info font-weight-bolder mt-2 mb-2" style= "font-size:20px;" data-toggle= "tooltip" data-placement= "top" title= "Issue the Permit to Work and send to Receiver" >Issue Permit To Work @ViewData[ "MyString" ] I got the following error

Marius Vasile · Answer

this ViewBag has to be a model and it is not

Sachin Singh · Answer

obviously you can use sir give it a try

Marius Vasile · Answer

But Sachin, can I use ViewBag in Razor pages? This is only for MVC

Marius Vasile · Answer

I can'y implement your solution because my check doesn't work as intended. Let try to work arround and update later

Yogeshkumar Hadiya · Answer

yes sir return error message or any variable with value and check in razor page with if block . if (condition){ //your code } else { return view ( "YourView" , new {error= "yes" }) }

Marius Vasile · Answer

So you are trying to say that in else statement I just add the error text? And it will be shown in browser? That simple? My variable is list type, how do I get this into model? Please give an example