有没有办法知道在 PageLoad 事件中是否按下了控件？

Question

I created 2 buttons programmatically. Now i want to know which one was pressed at the pageLoad time....The button will fire a page load event and then its own event..

Before it fires its own event, I want to know at the page load event if which button was pressed.

Is there a way to find out?

My buttons are like this

   Button btnMoveThread = new Button();
        btnMoveThread.Text = "1";
        btnMoveThread.Command += ModeratorButtonPassTo_Click;

   Button btnMoveThread = new Button();
        btnMoveThread.Text = "2";
        btnMoveThread.Command += ModeratorButtonPassTo_Click;

This function wont work:

 public static System.Web.UI.Control GetPostBackControl(System.Web.UI.Page page)
    {
        Control control = null;
        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 controls ...
                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;
                }
            }
        }
        return control;
    }

Answer 1

You can determine this by identifying which control caused the postback, prior to it's event handler being called. eg

string sender = page.Request.Params.Get("__EVENTTARGET");
Response.Write(sender);        

Answer 2

ASP.NET postback works by submitting a client side form with two additional values, __EVENTTARGET and __EVENTARGUMENT . ASP.NET uses these to determine which control to find, and which event to fire. You could do:

if (IsPostBack)
{
    string controlId = Request["__EVENTTARGET"];
    // Do something with the control Id.
}

Answer 3

You need to add the buttons before the post back so that you can get access to them during the post back, probably in the INIT of the page. I changed it so it would compile and added an ID property to the buttons:

    Button btnMoveThread = new Button();
    btnMoveThread.Text = "1";
    btnMoveThread.ID = "Thread1";
    btnMoveThread.Command += ModeratorButtonPassTo_Click;
    DivContent.Controls.Add(btnMoveThread);

    Button btnMoveThread2 = new Button();
    btnMoveThread2.Text = "2";
    btnMoveThread2.ID = "Thread2";
    btnMoveThread2.Command += ModeratorButtonPassTo_Click;
    DivContent.Controls.Add(btnMoveThread2);

Then, in your function you need to iterate over the keys of the request.form:

    int KeyCount = page.Request.Form.AllKeys.Length;
    for (int i = 0; i < KeyCount; i++)
    {
        if (page.Request.Form.AllKeys[i] == "Thread1")
        {
            return page.FindControl("Thread1");
        }
        if (page.Request.Form.AllKeys[i] == "Thread2")
        {
            return page.FindControl("Thread2");
        }
    }

Since you are adding the buttons in code and not in the designer the find control will be null unless you add them back before the postback, like I suggested in the INIT of the page.