Muhammad Akhtar Muhammad Akhtar - 2 months ago 32
ASP.NET (C#) Question

On postback, how can I check which control cause postback in Page_Init event

On postback, how can I check which control cause postback in Page_Init event.

protected void Page_Init(object sender, EventArgs e)
//need to check here which control cause postback?




I see that there is already some great advice and methods suggest for how to get the post back control. However I found another web page (Mahesh blog) with a method to retrieve post back control ID.

I will post it here with a little modification, including making it an extension class. Hopefully it is more useful in that way.

/// <summary>
/// Gets the ID of the post back control.
/// See:
/// </summary>
/// <param name = "page">The page.</param>
/// <returns></returns>
public static string GetPostBackControlId(this Page page)
    if (!page.IsPostBack)
        return string.Empty;

    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 controlName = page.Request.Params["__EVENTTARGET"];
    if (!String.IsNullOrEmpty(controlName))
        control = page.FindControl(controlName);
        // if __EVENTTARGET is null, the control is a button type and we need to
        // iterate over the form collection to find it

        // ReSharper disable TooWideLocalVariableScope
        string controlId;
        Control foundControl;
        // ReSharper restore TooWideLocalVariableScope

        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"))
                controlId = ctl.Substring(0, ctl.Length - 2);
                foundControl = page.FindControl(controlId);
                foundControl = page.FindControl(ctl);

            if (!(foundControl is IButtonControl)) continue;

            control = foundControl;

    return control == null ? String.Empty : control.ID;

Update (2016-07-22): Type check for Button and ImageButton changed to look for IButtonControl to allow postbacks from third party controls to be recognized.