<script runat="server">
Sub submit(Sender As Object, e As EventArgs)
label1.Text=txt1.Text
End Sub
</script>
<!DOCTYPE html>
<html>
<body>
<form runat="server">
Write some text:
<asp:TextBox id="txt1" Width="200" runat="server" />
<asp:Button id="b1" Text="Copy to Label" OnClick="submit" runat="server" />
<p><asp:Label id="label1" runat="server" /></p>
</form>
</body>
</html>