o_19mgorv9t13a3ko71fev19l81mqa.pdf

One of the nice features about the MVC client-side validation is that the same attributes used to specify validation rules are
applied at the client and at the server. This means that data from browsers that do not support JavaScript are subject to the same
validation as those that do, without requiring any additional effort.
MVC CLIENT VALIDATION VERSUS JQUERY VALIDATION
The MVC client-validation features are built on top of the jQuery Validation library. If you prefer, you can use the Validation
library directly and ignore the MVC features. The Validation library is flexible and feature-rich. It is well worth exploring, if
only to understand how to customize the MVC features to take best advantage of the available validation options. I cover the
jQuery Validation library in depth in my Pro jQuery 2.0 book, also published by Apress.
Performing Remote Validation
The last validation feature I will look at in this chapter is remote validation. This is a client-side validation technique that invokes an
action method on the server to perform validation.
A common example of remote validation is to check whether a username is available in applications when such names must be
unique; the user submits the data, and the client-side validation is performed. As part of this process, an Ajax request is made to
the server to validate the username that has been requested. If the username has been taken, a validation error is displayed so that
the user can enter another value.
This may seem like regular server-side validation, but there are some benefits to this approach. First, only some properties will
be remotely validated; the client-side validation benefits still apply to all the other data values that the user has entered. Second, the
request is relatively lightweight and is focused on validation, rather than processing an entire model object.
The third difference is that the remote validation is performed in the background. The user doesn’t have to click the submit
button and then wait for a new view to be rendered and returned. It makes for a more responsive user experience, especially when
there is a slow network between the browser and the server.
That said, remote validation is a compromise. It strikes a balance between client-side and server-side validation, but it does
require requests to the application server, and it is not as quick to validate as normal client-side validation.
The first step toward using remote validation is to create an action method that can validate one of the model properties. I am
going to validate the Date property of the Appointment model to ensure that the requested appointment is in the future.
(This is one of the original validation rules I used at the start of the chapter, but which isn’t possible to validate using the standard
client-side validation features.) In Listing 25-24, you can see the ValidateDate action method that I added to the Home
controller.
Listing 25-24. Adding a Validation Action Method to the HomeController.cs File
using System;
using System.Web.Mvc;
using ModelValidation.Models;
namespace ModelValidation.Controllers {
public class HomeController : Controller {
public ViewResult MakeBooking() {
return View(new Appointment { Date = DateTime.Now });
}
[HttpPost]
public ViewResult MakeBooking(Appointment appt) {
if (ModelState.IsValid) {
// statements to store new Appointment in a
// repository would go here in a real project
return View("Completed", appt);
} else {
return View();
}
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