Client Validation using Asp Validator

Client Side Validation with ASP Validators

If the user is working with a browser that supports dynamic HTML (DHTML), ASP.NET validation controls can perform validation using client script. Because the controls can provide immediate feedback without a round trip to the server, the user experience with the page is enhanced.

We will be using of the client side APIs amongst the below  ones :

Client Page Variable	Server Page Property
Page_IsValid	IsValid
Page_Validators (array)   Contains references to all validation controls on the page.	Validators (collection)   Contains references to all validation controls.
Page_ValidationActive    A Boolean value that indicates whether validation should take place. Set this variable to false to turn off client-side validation programmatically.	(no equivalent)

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Code Snippet :

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<asp:Label ID="UserNameLabel" runat="server">Username:</asp:Label>

               <asp:TextBox ID="UserName" runat="server"></asp:TextBox>

<asp:RequiredFieldValidator ID="UserNameRequired" runat="server" 

ControlToValidate="UserName" ErrorMessage="User Name is required." ToolTip="User Name is required." ValidationGroup="LoginUserValidationGroup">*</asp:RequiredFieldValidator>

<asp:Label ID="PasswordLabel" runat="server">Password:</asp:Label>

               <asp:TextBox ID="Password" runat="server"></asp:TextBox>

<asp:RequiredFieldValidator ID="PasswordRequired" runat="server" 

ControlToValidate="Password" ErrorMessage="Password is required." ToolTip="Password is required." ValidationGroup="LoginUserValidationGroup">*</asp:RequiredFieldValidator>

<asp:Button ID="LoginButton" runat="server" CommandName="Login" Text="Log In" ValidationGroup="LoginUserValidationGroup"

               OnClientClick="performCheck();" />

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Now we will be writing script in our script file to check if the validations are performed correctly, then only postback the page else show the respective error messages :

function performCheck() {             Page_ClientValidate("LoginUserValidationGroup");             if (Page_IsValid) {                 alert('it is valid');                 return true;             }             else {                 alert('No valid');                 return false;             }         }

In other way, you can directly use Page_ClientValidate method:

function performCheck() {                    if (Page_ClientValidate("LoginUserValidationGroup")) {                 alert('it is valid');                 return true;             }             else {                 alert('No valid');                 return false;             }