Question

I’ve written a small extention method for a page control, to recursively search for a control. But I get the “Object reference not set to an instance of an object” exception.

And it seems page.Controls only has 1 control and on this control I et this exception.

Anyone has any idea?

Here is the code:

public static Control FindControlRecursive(this Page page, string id)
        {
            return Execute(page, id);
        }

 private static Control Execute(Control root, string id)
        {
            if (root.ID.Equals(id))
                return root;
              ControlCollection  controls = root.Controls;

            foreach (Control ctrl in controls)
            {
                Control FoundControl = Execute(ctrl, id);
                if (FoundControl != null)
                    return FoundControl;
            }
            return null;
        }
    }

Update
Now I have another error:
Error occured: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index …

But this one throws somewhere in middle of the looping.

Answer 1

There is one possible cause in this line:

if (root.ID.Equals(id))

ID property is not necessary set for all controls in the tree. I even doubt whether it is not null for Page itself. Try replacing this line with something like:

if (string.Equals(root.ID, id))