/// <summary>
/// Returns the sender ID of the post back received by ASP.net. 
/// (Usually a button's ID)
/// </summary>
/// <returns></returns>
private string GetPostBackSender()
{
	return Request.Params.Get("__EVENTTARGET");
}

/// <summary>
		/// Returns the sender ID of the post back received by ASP.net. 
		/// (Usually a button's ID)
		/// </summary>
		/// <returns></returns>
		private string GetPostBackSender()
		{
			return Request.Params.Get("__EVENTTARGET");
		}

Returns the postback sender ID.  This is usually a button ID from a form that caused a post back.

ASP.net: Retrieve PostBack sender (on Page_Load)

aspnet

C#