<head runat="server">
<title></title>
<script language="c#" runat="server">
protected void btnShowId_Click( object sender,EventArgs e )
{
string id= GenerateID(txtIdPre.Text);
txtId.Text = id;
}
private string GenerateID(string pre)
{
string id = null;
id=pre+"_"+DateTime.Now.ToString();
return id;
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
ID Prefix: <asp:textbox id="txtIdPre" runat="server"</asp:textbox>
<asp:button id="btnShowId" runat="server" text="Show Id" onclick="btnShowId_Click" />
Your generated Id:<asp:textbox id="txtId" runat="server" </asp:textbox>
</div>
</form>
</body>