How can I implement AJAX validation in ASP.NET?

How can I implement AJAX validation in ASP.NET?

You can implement AJAX validation in ASP.NET by using jQuery to send asynchronous requests to your server-side validation methods.

Can you provide a code example for that?

Sure! You can use the jQuery $.ajax method to call your validation action. Here's a simple example:

$.ajax({
    type: 'POST',
    url: '/YourController/ValidateMethod',
    data: { inputField: $('#inputField').val() },
    success: function(response) {
        // Handle the response from the server
        if(response.isValid) {
            // Proceed with form submission
        } else {
            // Show validation error
            $('#errorMessage').text(response.errorMessage);
        }
    }
});

What should the server-side method look like?

The server-side method should return a JSON object indicating whether the input is valid. Here's an example:

[HttpPost]
public JsonResult ValidateMethod(string inputField) {
    bool isValid = !string.IsNullOrEmpty(inputField);
    string errorMessage = isValid ? null : "Input cannot be empty.";
    return Json(new { isValid, errorMessage });
}