I know... need and event from client script to server...

Somebody has write this code?

Thanks 

Hi,

Thank you for your post!

There are two ways to do this:

1.using window.onbeforeunload() event, do it like this:

function  window.onbeforeunload()  {  alert("close the window?")}

or

function  window.onbeforeunload()  { 
 if  (event.clientX>document.body.clientWidth  &&  event.clientY<0 ||event.altKey) 
     window.event.returnValue="Are you sure?";
 }

2.using onUnload event

body onUnload="myClose()"

If you have further questions, let me know! 

Best Regards,

Hi-

Thanks a lot for your help. I did know the client side code. I wish complement reply with the server side code.

My original question is "How to know if user close the browser or navigate to another page ?"... missing: "I need run something in backend".
Right, to send an event to server side from client, we need a callback. I am working an approach that’s works fine:

Simple sample:
...
using System.IO;
...
public partial class test : System.Web.UI.Page, System.Web.UI.ICallbackEventHandler
{
    protected void Page_Load(object sender, EventArgs e)
    {
        ClientScriptManager cs = Page.ClientScript;
        string er = ClientScript.GetCallbackEventReference(this, "", "null", "null", "null", true);
        string rb = "function callServerTask(arg) {" + er + ";}";
        cs.RegisterClientScriptBlock(this.GetType(), "callServerTask", rb, true);
        // body has attribute rutat=server id=body
        body.Attributes.Add("onunload", "callServerTask('');return false;");
    }
    public void RaiseCallbackEvent(string eventArgument)
    {
        CloseMe();
    }
    public string GetCallbackResult()
    {
        return "";
    }
    private void CloseMe()
    {
        // to test that callback works
        StreamWriter s = new StreamWriter(Server.MapPath("closehistory.txt"), true);
        s.WriteLine("close at:" + DateTime.Now.ToString());
        s.Close();
    }
}

Warning: In IDE of Visual Studio works when navigate to another page. In production, works always.

Regards.