Accessing the children of an expander control

Question

I have a textblock inside the ContentTemplate of an Expander. I want to access that textblock in my code behind file. This is what I have tried so far

Answer 1

I've tried your code, it's almost fine. I've tried testing it on such as a Button first, it works OK. However for the Expander, it's more complex. There are 2 notices here:

• Be sure the Expander is expanded (IsExpanded = true).
• Be sure the layout is updated (you can call UpdateLayout explicitly)

So the code should be:

yourExpander.IsExpanded = true;
yourExpander.UpdateLayout();
//now use your method
var textBlock = FindVisualChild(yourExpander);

Your code can be shorten more like this:

private childItem FindVisualChild(DependencyObject obj) 
                               where childItem : DependencyObject
{
    for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
    {
        DependencyObject child = VisualTreeHelper.GetChild(obj, i);
        if(child is childItem) return (childItem)child;            
        childItem childOfChild = FindVisualChild(child);
        if (childOfChild != null) return childOfChild;            
    }
    return null;
}

Note that child will never be null. Because the GetChildrenCount() already limits the range of existing children, so the child should exist at the specified index i.