Question

How can I return custom validation messages using JsonResult and AJAX?

Here is my controller action to add a student in StudentDB.

UPDATED:

    [HttpPost()]
    public ActionResult AddStudent(string studentName, int studentId)
    {
        var studentPresent = studentTable.Students.Where(s => s.StudentID == studentId&& b.StudentName == studentName);

        if (studentPresent == null || !studentPresent .Any())
        {
            var student = new Student()
                {
                    StudentName = studnetName,
                    StudentID = studentId,
                };
            studentTable.AddObject("Student", student);
            studentTable.SaveChanges();

         }
        return new JsonResult();      

    }

Here is my JavaScript:

function addStudent() {
    $.ajax({
        type: 'POST',
        url: '/StudentAdmin/AddStudent',
        data: {
            studentName: $('#studentName').val(),
            studentNumber: GetTextBoxValue('#studentNumber'),            
        },
        success: function (result) {
            if ($('#studentPresent').val() == null) {
            showMessage('Success', 'Student saved successfully.', '', false);                
        } else {
            showMessage('Error', 'Student already present in database.', '', false);
        }
            GetGrid('#studentGrid').ajaxRequest();
            hideForm();
        },
        studentPresent: function (result) {
            showMessage('Error', 'Student Already present in Database.', '', true);
        }

    });
}

I want to display the “error” message if this student is already present in database.
Also, Is there a way of passing more validation messages to JasonResult?

Thanks in advance.

Answer 1

You can pass any object to the JsonResult object and it will be serialized (or it will attempt to serialize) down to the javascript.

return new JsonResult(new { Anything = "Hello World" });

That results in a JSON object like so:

{"Anything":"Hello World"}

Being rendered to your javascript in the result variable.

Your code above actually doesn’t show any error message being generated; you would need a try / catch block if you want to get the text of the SQL exception.

EDIT:

You would have code like so:

return Json(new { message = "Success" }); // success message
return Json(new { message = "Failure" }); // fail message

And then in javascript, your callback is like so:

success: function(result)
{
     if(result.message == "Success")
       // Show success message
     else
       // Show Error Message
}