how to access a textbox in a grid in a stackpanel

Question

I have the following code:

<StackPanel x:Name="ContentStackPanel">
            <Grid>
                <TextBlock Text="Min Value" />
                <TextBox Text="{Binding MinValue}" />
            </Grid>
            <Grid>
                <TextBlock Text="Max Value" />
                <TextBox Text="{Binding MinValue}" />
            </Grid>
</StackPanel>

I want to add a button so that I can clear the text in both TextBoxes. This code doesn't work

        private void ClearAllClick(object sender, RoutedEventArgs e)
        {
             foreach (TextBox tb in ContentStack.Children)
             {
                 tb.Text = String.Empty;
             }
        }

how do I access the textbox inside the grid of ContentStackPanel?

Answer 1

The Children property only gives you immediate children, not all descendants. You could write a helper method to traverse the tree:

private void ClearAllClick(object sender, RoutedEventArgs e)
{
    ClearTextChildren(ContentStackPanel);
}

private void ClearTextChildren((Panel container)
{
    foreach (var element in container.Children)
    {
        if (element is TextBox)
            ((TextBox)element).Text = String.Empty;
        else if (element is Panel)
            ClearChildren((Panel)element);
    }
}

---

An alternative approach (probably better, since it's fragile to traverse UI trees in code) would be to use a Command implementation on the button, instead of a click handler. This will allow you to clear the view-model properties instead of the text boxes themselves.

<Button x:Name="ClearAll" Command="{Binding ClearAllCommand}" />

"ClearAllCommand" should be in the same place as "MinValue" and "MaxValue":

public ICommand ClearAllCommand { get; private set; }

Using a standard DelegateCommand implementation :

ClearAllCommand = new DelegateCommand(arg => {
    MinValue = null;
    MaxValue = null; 
});