WPF: Problem with overlapping controls and grid column widths

Well I have got a bit of a kludge working, I'll explain how for future generations:

Essentially I have a 2 column, multi row grid with a splitter right aligned in the first column so it can be resized by the user if the content it contains requires more space. To complicate things I have a user control being loaded programatically into some of the rows which has a columnSpan of 2 for rendering purposes (content 'bleeds' from one cell into the next).

When the first column is resized I need this to be reflected in the usercontrol. Firstly I tried binding to the ColumnDefinition but it really wasn't playing ball.

How I fixed/Kludged it

In a spare cell in the first column I added a <Label> with an x:Name to make it accessible. As it is in a cell it has default properties of 'Stretch' and fills the cell completely. It gets resized as the column is resized using the splitter. Binding to the Label's ActualWidth property means that changes to the size of the column are communicated to the DependancyProperty in my columnSpanned usercontrol correctly.

Thoughts

Obviously, despite ColumnDefinition having an ActualWidth property when it changes it doesn't appear to fire the PropertyChanged event internally (or thats my best guess). This may be a bug, or by design, but for me it means I've had to use a less clean solution.

I combined the template format used by John Myczek and Tri Q's algorithm above to create a findChild Algorithm that can be used on any parent. Keep in mind that recursively searching a tree downwards could be a lengthy process. I've only spot-checked this on a WPF application, please comment on any errors you might find and I'll correct my code.

WPF Snoop is a useful tool in looking at the visual tree - I'd strongly recommend using it while testing or using this algorithm to check your work.

There is a small error in Tri Q's Algorithm. After the child is found, if childrenCount is > 1 and we iterate again we can overwrite the properly found child. Therefore I added a if (foundChild != null) break; into my code to deal with this condition.

/// <summary>
/// Finds a Child of a given item in the visual tree. 
/// </summary>
/// <param name="parent">A direct parent of the queried item.</param>
/// <typeparam name="T">The type of the queried item.</typeparam>
/// <param name="childName">x:Name or Name of child. </param>
/// <returns>The first parent item that matches the submitted type parameter. 
/// If not matching item can be found, 
/// a null parent is being returned.</returns>
public static T FindChild<T>(DependencyObject parent, string childName)
   where T : DependencyObject
{    
  // Confirm parent and childName are valid. 
  if (parent == null) return null;

  T foundChild = null;

  int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
  for (int i = 0; i < childrenCount; i++)
  {
    var child = VisualTreeHelper.GetChild(parent, i);
    // If the child is not of the request child type child
    T childType = child as T;
    if (childType == null)
    {
      // recursively drill down the tree
      foundChild = FindChild<T>(child, childName);

      // If the child is found, break so we do not overwrite the found child. 
      if (foundChild != null) break;
    }
    else if (!string.IsNullOrEmpty(childName))
    {
      var frameworkElement = child as FrameworkElement;
      // If the child's name is set for search
      if (frameworkElement != null && frameworkElement.Name == childName)
      {
        // if the child's name is of the request name
        foundChild = (T)child;
        break;
      }
    }
    else
    {
      // child element found.
      foundChild = (T)child;
      break;
    }
  }

  return foundChild;
}

Call it like this:

TextBox foundTextBox = 
   UIHelper.FindChild<TextBox>(Application.Current.MainWindow, "myTextBoxName");

Note Application.Current.MainWindow can be any parent window.