Calling a JavaScript function from codebehind is quiet simple, yet it confuses a lot of developers. Here's how to do it. Declare a JavaScript function in your code as shown below:
JavaScript
<head runat="server"> <title>Call JavaScript From CodeBehind</title> <script type="text/javascript"> function alertMe() { alert('Hello'); } </script> </head>
In order to call it from code behind, use the following code in your Page_LoadC#
protected void Page_Load(object sender, EventArgs e) { if (!ClientScript.IsStartupScriptRegistered("alert")) { Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", "alertMe();", true); } }
VB.NET
If (Not ClientScript.IsStartupScriptRegistered("alert")) Then Page.ClientScript.RegisterStartupScript(Me.GetType(), "alert", "alertMe();", True) End If
The Page.ClientScript.RegisterStartupScript() allows you to emit client-side script blocks from code behind. More info here http://msdn.microsoft.com/en-us/library/system.web.ui.clientscriptmanager.registerstartupscript.aspx
To call the JavaScript code on a button click, you can add the following code in the Page_Load
btnCall.Attributes.Add("onclick", " return alertMe();");
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