ASP.NET 4.5 has been improved and latest version ASP.NET. It includes an array of new and modified features. Today we’ll discuss one new feature Unobtrusive Validation that is introduced with ASP.NET 4.5 .

So what is Unobtrusive Validation?

In a normal validation scenario,when we use a validator to validate any any control and use Client side validation, some JavaScript is generated and rendered as HTML. Also some supportive JavaScript files is also get loaded by the browser for the validation.

Now with feature Unobtrusive Validation, inline JavaScript is not generated and rendered to handle the Client Side validation. Instead of this it uses HTML5 data-* attributes for all these validation.

So now lets see a normal scenario. I have taken textbox and applied two ASP.NET validators on it. One is RequiredFieldValidator and RangeValidator that allows to enter the value between 100 and 1000. Let’s see the aspx code.

Now Lets run the application and see the generated the HTML. Now if you look at the View Source of the page

To handle these validation, it generates the lots of JavaScript code on the page. It is

Now I have made the same application with Visual Studio 2011 Developer Preview. By default Unobtrusive Validation is enabled here. So lets see the generated HTML

Now if you see the above generated HTML, there are few data-* attributes are rendered. And these hold all the required information of the validator. And there is no inline JavaScript code generated. This reduces the significant amount of page size because here inline JavaScript code is not generated and this also makes the rendered HTML neat and clean.

So let’s see how 4.5 allows to configure the Unobtrusive Validation. There is one new property UnobtrusiveValidationMode got added, which can be assigned two values

None : means UnobtrusiveValidation is set to off
WebForms : means UnobtrusiveValidation is enabled

This property can be configured at three places in application. These are

1. First it can be set at application level in config file. We need to add it in the <appSettings> element.

add name="ValidationSettings:UnobtrusiveValidationMode" value="WebForms" />

As I discussed it is by default enabled in The above key by default added in web.config. So if you want to disable it then change the above as

<add name="ValidationSettings:UnobtrusiveValidationMode" value="None" />

2. We can also set it at Application_Start method in Global.asaxfile as

void Application_Start(object sender, EventArgs e)
   //Enabling UnobtrusiveValidation application wide
   ValidationSettings.UnobtrusiveValidationMode = UnobtrusiveValidationMode.WebForms;

3. We can also set it at page level by setting the property of Page Class as

Page.UnobtrusiveValidationMode = System.Web.UI.UnobtrusiveValidationMode.WebForms;