How to reference a user control in its own code behind? - asp.net

Question

Let's say I have a user control with a couple of buttons. I'd like to know which one caused the postback, using this method:
public static Control GetPostBackControl(Page page)
{
Control control = null;
string ctrlname = page.Request.Params.Get("__EVENTTARGET");
if (ctrlname != null && ctrlname != string.Empty)
{
control = page.FindControl(ctrlname);
}
else
{
foreach (string ctl in page.Request.Form)
{
Control c = page.FindControl(ctl);
if (c is System.Web.UI.WebControls.Button)
{
control = c;
break;
}
}
}
return control;
}
And this is how I am calling it:
string btn = GetPostBackControl(this.Page).ID;
I'm getting the "Object reference not set to an instance of an object." I know now that the problem comes from the fact that I'm using this.Page, which represents the parent page.
How to reference the user control that I'm in? (not the parent page) So that it can work with the method to find the button that caused the postback?
Thanks for helping.
EDIT
Both buttons are located inside the user control. GetPostBackControl() is also in the code-behind of the user control.

Answer 1

I did a quick example on your given code and it worked out pretty fine. Perhaps you did miss checking for Page.IsPostBack? Obviously there will only be a postBackControl if there is a postBack...
#Buttons - they will be rendered as <input type="submit"> so they won't appear within ___EVENTTARGET. That's why Ryan Farlay wrote in his blog
However, you can still get to it, just in a different way. Since the
button (or input) is what causes the form to submit, it is added to
the items in the Form collection, along with all the other values from
the submitted form. [...] If you were to
look in the Form collection for anything that is a button then that
will be what caused the postback (assuming that it was a button that
caused the page to submit). If you first check the __EVENTTARGET, then
if that is blank look for a button in the Form collection then you
will find what caused the postback
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack)
{
Control postBackControl = GetPostBackControl(this.Page);
Debug.WriteLine("PostBackControl is: " + postBackControl.ID);
}
}
public static Control GetPostBackControl(Page page)
{
Control control = null;
string ctrlname = page.Request.Params.Get("__EVENTTARGET");
if (ctrlname != null && ctrlname != string.Empty)
{
control = page.FindControl(ctrlname);
}
else
{
foreach (string ctl in page.Request.Form)
{
Control c = page.FindControl(ctl);
if (c is System.Web.UI.WebControls.Button)
{
control = c;
break;
}
}
}
return control;
}