Which control caused the postback?

I have two buttons:

<asp:Button ID="Button1" runat="server" Text="Button" />
<asp:Button ID="Button2" runat="server" Text="Button" />

How can I determine on pageLoad which one of this two caused the postback? Is there a short solution as I know there are only two controls that can cause this postback?

Solution 1:

You can use this method to get the control that caused the postback:

/// <summary>
/// Retrieves the control that caused the postback.
/// </summary>
/// <param name="page"></param>
/// <returns></returns>
private Control GetControlThatCausedPostBack(Page page)
{
    //initialize a control and set it to null
    Control ctrl = null;

    //get the event target name and find the control
    string ctrlName = page.Request.Params.Get("__EVENTTARGET");
    if (!String.IsNullOrEmpty(ctrlName))
        ctrl = page.FindControl(ctrlName);

    //return the control to the calling method
    return ctrl;
}

Solution 2:

http://geekswithblogs.net/mahesh/archive/2006/06/27/83264.aspx

private string getPostBackControlName()
    {
        Control control = null;
        //first we will check the "__EVENTTARGET" because if post back made by       the controls
        //which used "_doPostBack" function also available in Request.Form collection.

        string ctrlname = Page.Request.Params["__EVENTTARGET"];
        if (ctrlname != null && ctrlname != String.Empty)
        {
            control = Page.FindControl(ctrlname);
        }

        // if __EVENTTARGET is null, the control is a button type and we need to
        // iterate over the form collection to find it
        else
        {
            string ctrlStr = String.Empty;
            Control c = null;
            foreach (string ctl in Page.Request.Form)
            {
                //handle ImageButton they having an additional "quasi-property" in their Id which identifies
                //mouse x and y coordinates
                if (ctl.EndsWith(".x") || ctl.EndsWith(".y"))
                {
                    ctrlStr = ctl.Substring(0, ctl.Length - 2);
                    c = Page.FindControl(ctrlStr);
                }
                else
                {
                    c = Page.FindControl(ctl);
                }
                if (c is System.Web.UI.WebControls.Button ||
                         c is System.Web.UI.WebControls.ImageButton)
                {
                    control = c;
                    break;
                }
            }

        }

        if (control != null)
            return control.ID;
        else
            return string.Empty;
    }

Solution 3:

This helps to find the name of control that caused postback in pageload.This helped me.Hope this helps someone else too

  <asp:Button ID="Button1" runat="server" Text="Button"
  OnClientClick = "SetSource(this.id)" />

   <asp:ImageButton ID="ImageButton1" runat="server"
    OnClientClick = "SetSource(this.id)" />

            <script type = "text/javascript">
            function SetSource(SourceID)
          {
    var hidSourceID =
    document.getElementById("<%=hidSourceID.ClientID%>");
    hidSourceID.value = SourceID;
    }
    </script>

 on code behind you can get the ID of the function using :
 if (IsPostBack)
 {
   string CtrlID = string.Empty;
  if (Request.Form[hidSourceID.UniqueID] != null &&
       Request.Form[hidSourceID.UniqueID] != string.Empty)
    {
     CtrlID = Request.Form[hidSourceID.UniqueID];
   }
}

Solution 4:

To add to this: you can find which event caused the postback with:

Page.Request.Params.Get("__EVENTARGUMENT")