ASP.NET Web Forms - Manually Trigger Client Side Validation

Lets say you have a web form with one more serverside controls like one below,

<asp:TextBox ID="txtEmail" runat="server" class="txtBoxLarge textSmall" placeholder="Enter Email Address"></asp:TextBox>
<asp:RequiredFieldValidator ID="rfvEmail" runat="server" ErrorMessage="Enter Email" Display="None" ControlToValidate="txtEmail" ValidationGroup="groupName"></asp:RequiredFieldValidator>

And you need to do some client side operations along with client side validation, the button triggering the whole operation will be like,

<asp:Button ID="btnSubmit" CssClass="blueBtnLarge" runat="server" Text="Continue" ValidationGroup="groupName" OnClick="btnSubmit_Click" OnClientClick="ClientSideClick(this)" UseSubmitBehavior="False" />

Here OnClick will send request to server side and OnClientClick will execute on client side before control passed to server. OnClick only will be triggered if OnClientClick returned true.

And the client side JavaScript function we call on OnClientClick will be like below,

<script type="text/javascript">
    function ClientSideClick(myButton) {
        // Any operation before validation goes here

        // Client side validation
        if (typeof (window.Page_ClientValidate== 'function') {
            if (window.Page_ClientValidate('groupName'=== false) {
                document.getElementById('someDivElementWithErrorExplanation').style.display = 'block'// Showing error on validation, modify to your needs
                return false;
        document.getElementById('someDivElementWithErrorExplanation').style.display = 'none';
        // Any operation after client side validation passess goes here.

        return true;

That's it. Also, don't forget to notice the usage of the ValidationGroup all over the code above.

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  • Abhith


    Abhith Rajan is a full-stack developer, consultant, Sysberries employee, and biker. Who passionate about C# and JavaScript. Works on his blog, his personal finance web app and its react native mobile app in his free time.

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