C#-Code:

namespace Liuw.Net.WindowsControlLibrary
{
    public partial class MyControl1 : UserControl
    {
        public MyControl1()
        {
            InitializeComponent();
        }
        private string _userName = "";
        public string UserName
        {
            set { _userName = value; }
            get { return _userName; }
        }
        public void SayHello()
        {
            MessageBox.Show("Welcome To Liuwu.net," + _userName);
        }
    }
}

ASP.NET-Code:

<script type="text/javascript">
function SayHello()
{
    var obj = document.getElementById("ctl");
    var input = document.getElementById("inputName");
    obj.UserName = input.value;
    obj.SayHello();       
}
</script>
Name:<input type="text" id="inputName" /><br />
<input type="button" value="SayHello" onclick="SayHello()" />
<object id="ctl"   classid="Liuw.Net.WindowsControlLibrary.dll# Liuw.Net.WindowsControlLibrary.MyControl1"></object>