this.Controls returns null

Question

There are similar questions to this on here but nothing that answers this specific issue. I'm creating a button object to dynamically amend the Image on the button. But using the code below, I get a "Object reference is not set to an instance of an object" when I try and set the Image on the button.

Button button3;
button3 = (Button)this.Controls["btnDay" + ctrlsFwd.ToString("00")];
button3.Image = Resources.BookingAllDay;

Any help appreciated! Go easy - it's my first post :-)

** Update - A bit of a facepalm moment. The buttons are in a panel, so I needed to refer to pnlCalendar.Controls and not this.Controls.

Answer 1

One way of doing this would be:

button3 = (Button)this.Controls
    .Find("btnDay" + ctrlsFwd.ToString("00"))
    .FirstOrDefault();

another way of doing it would be:

button3 = this.Controls.OfType<Button>()
    .Where(b => b.Name == "btnDay" + ctrlsFwd.ToString("00"))
    .FirstOrDefault();

As pointed out by Stefan , check for null :

if (button3 == null) { return; }

because it can happen.

Answer 2

Since this, button3 = (Button)this.Controls["btnDay" + ctrlsFwd.ToString("00")]; , is a perfectly valid way of accessing a control, and doesn't work, either a control with that name doesn't exist or more likely the control is inside a container. Either way searching for it in this isn't going to find it no matter how many different ways you try and find it.