Hi ,
Make
Enabled = false ;
protected void Button1_Click(object sender, EventArgs e)
{
TextBox1_CalendarExtender.Enabled = true;
}
<div>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:CalendarExtender ID="TextBox1_CalendarExtender" runat="server"
Enabled="false" TargetControlID="TextBox1">
</asp:CalendarExtender>
<asp:Button ID="Button1" runat="server" Text="Button" onclick="Button1_Click" />
</div>
Best Regards
M.Mitwalli