Question

I have a list box that contains items that are represented by a single textbox.

When the user clicks a button, I want to iterate thru all these text boxes and check if their binding expressions are clean of errors; Should be something like:

    Dim errCount = 0     For Each item In MyListBox.ListBoxItems 'There is no such thing ListBoxItems which is actually what I am looking for.         Dim tb As TextBox = item '.........Dig in item to extract the textbox from the visual tree.         errCount += tb.GetBindingExpression(TextBox.TextProperty).HasError     Next     If errCount Then         'Errors found!     End If 

Any discussion would be really appreciated. Thanks.

Answer 1

There may be an easier way to do this, but here is one option that will work:

1) Iterate through the list of items.

Because you are using items source, ListBox.Items will refer to the data items in the ItemsSource.

for (int i = 0; i < ListBox.Items.Count; i++) {     // do work as follows below... } 

2) Get the containers for these items.

DependencyObject obj = ListBox.ItemContainerGenerator.ContainerFromIndex(i); 

3) Use VisualTreeHelper to search for a TextBox child of the container visual.

TextBox box = FindVisualChild<TextBox>(obj); 

Use this function to search for a visual child of the correct type:

public static childItem FindVisualChild<childItem>(DependencyObject obj)     where childItem : DependencyObject {     // Search immediate children     for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)     {         DependencyObject child = VisualTreeHelper.GetChild(obj, i);          if (child is childItem)             return (childItem)child;          else         {             childItem childOfChild = FindVisualChild<childItem>(child);              if (childOfChild != null)                 return childOfChild;         }     }      return null; } 

4) Finally, examine the binding on the TextBox.

All put together, something like this:

private bool ValidateList(ListBox lb) {     for (int i = 0; i < lb.Items.Count; i++)     {         DependencyObject obj = lb.ItemContainerGenerator.ContainerFromIndex(i);         TextBox box = FindVisualChild<TextBox>(obj);         if (!TestBinding(box))             return false;     }      return true; }