How to know which control has raised a postback?

public string GetPostBackControl(System.Web.UI.Page page)

    {

        Control ctrl1 = null;

        Control ctrl2 = null;

        string ctrlName = page.Request.Params["__EVENTTARGET"];

        string ctrlStr = string.Empty;

        if (ctrlName != null && ctrlName != String.Empty)

        {

            ctrl1 = page.FindControl(ctrlName);

        }

        else

        {

            foreach (string ctl in page.Request.Form)

            {

                if (ctl.EndsWith(".x") || ctl.EndsWith(".y"))

                {

                    ctrlStr = ctl.Substring(0, ctl.Length - 2);

                    ctrl2 = page.FindControl(ctrlStr);

                }

                else

                {

                    ctrl2 = page.FindControl(ctl);

                }

                if (ctrl2 is System.Web.UI.WebControls.Button || ctrl2 is System.Web.UI.WebControls.ImageButton)

                {

                    ctrl1 = ctrl2;

                    break;

                }

            }

        }

        return ctrl1.ClientID;

    }

FileUpload control in asp.net

I have given a example below how to upload file using asp.net FileUpload control.

follow the instruction

1. Drag a file upload control and one button in source code

2. Drag a image control to show the uploaded image

3.Create a folder  name it img

<form id="form1" runat="server">

    <div>

   

        <asp:FileUpload ID="FileUploadControl" runat="server" />

        <asp:Button ID="btnUpload"

            runat="server" Text="Upload" onclick="btnUpload_Click" />

        <br />

        <br />

        <asp:Image ID="Myimage" runat="server" />

    </div>

    </form>

4. copy the code behind below at your button click event

protected void btnUpload_Click(object sender, EventArgs e)

    {

        if (FileUploadControl.HasFile)

        {

            string filename = Path.GetFileName(FileUploadControl.FileName);

            FileUploadControl.SaveAs(Server.MapPath("~/img/")+filename);

            Myimage.ImageUrl = "~/img/" + filename;

        }

    }