In my previous tutorials, I’d explained how to show alert message from client-side, how to call javascript function from code-behind, confirm message box example using javascript and more cracking tutorials on Asp.net, JavaScript, jQuery here.
Now here in this tutorial, I’ll explain how to show alert message box from server-side or code-behind in asp.net using c# or vb.net with example code.
Show Alert Message from Code-behind – [.aspx]
Following is the complete HTML Markup code that I used in my .aspx page for this demonstration:
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title>How to show alert message from code-behin in Asp.net</title>
<script type="text/javascript">
function alertMessage() {
alert('JavaScript Function Called!');
}
</script>
</head>
<body>
<form id="form1" runat="server">
<h4>Show alert message from code-behin in Asp.net</h4>
<div>
<asp:Button ID="btnClientSide" runat="server" OnClientClick="alertMessage()"
Text="Client-side" />
<asp:Button ID="btnServerSideMethod1" runat="server" Text="Server-side(Method1)"
OnClick="btnServerSideMethod1_Click" />
<asp:Button ID="btnServerSideMethod2" runat="server" Text="Server-side(Method2)"
OnClick="btnServerSideMethod2_Click" />
</div>
</form>
</body>
</html>
You can see, i’d added OnClientClick=”alertMessage()” when calling function from client-side. In case of calling javascript function from server-side or code-behind, we need OnClick event as OnClick=”btnServerSideMethod1_Click” and OnClick=”btnServerSideMethod2_Click”.
We need to use ScriptManager.RegisterStartupScript() method to achieve this. Here is the syntax for this method:
ScriptManager.RegisterStartupScript(Control control, Type type, string key, string script, bool addScriptTags);
Now define that event in code-behind as shown below.
Show Alert Message From Code-behind In C# – [.cs]
Following is the C# code:
//This method is used when you defined javascript function and want to call it
//So call pre-defined method this way
protected void btnServerSideMethod1_Click(object sender, EventArgs e) {
ScriptManager.RegisterStartupScript(this, GetType(), "alertMessage", "alertMessage();", true);
}
//This method is used when you don't want to define javascript method client-side
//So call directly this way
protected void btnServerSideMethod2_Click(object sender, EventArgs e) {
ScriptManager.RegisterStartupScript(this, GetType(), "alertMessage",
"alert('Called from code-behind directly!');", true);
}
OR
If you are dealing with asp.net UpdatePanel and UpdateProgress, use the following code:
//Following statement is used to call pre-defined javascript function
protected void btnServerSide_Click(object sender, EventArgs e) {
ScriptManager.RegisterStartupScript(myUpdatePanelID, myUpdatePanelID.GetType(), "myAlert",
"alert('Called from code-behind directly!');", true);
}
Show Alert Message From Code-behind In Vb.net – [.vb]
Likewise, following is the Vb.net code to display or show alert message:
'This method is used when you defined javascript function and want to call it'
'So call pre-defined method this way'
Protected Sub btnServerSideMethod1_Click(ByVal sender As Object, ByVal e As EventArgs)
ScriptManager.RegisterStartupScript(Me, Me.GetType(), "alertMessage", "alertMessage();", True)
End Sub
'This method is used when you don't want to define javascript method client-side'
'So call directly this way' Protected Sub btnServerSideMethod2_Click(ByVal sender As Object, ByVal e As EventArgs)
ScriptManager.RegisterStartupScript(Me, Me.GetType(), "alertMessage",
"alert('Called from code-behind directly!');", True)
End Sub
OR
If you are dealing with asp.net UpdatePanel and UpdateProgress, use the following code:
'Following statement is used to call pre-defined javascript function'
Protected Sub btnServerSide_Click(ByVal sender As Object, ByVal e As EventArgs)
ScriptManager.RegisterStartupScript(myUpdatePanelID, myUpdatePanelID.GetType(),
"myAlert", "alert('Called from code-behind directly!');", True)
End Sub
Example Result
