Question

I am using this code to simulate the tab functionality in my silverlight application.

I would really like to avoid writing the function a lot of times because it has to be used on quite a lot of textboxes throughout the application. I have created a static class

public static class TabInsert
{
    private const string Tab = "    ";
    public static void textBox_KeyDown(object sender, KeyEventArgs e)
    {
        TextBox textBox = sender as TextBox;
        if (e.Key == Key.Tab)
        {
            int selectionStart = textBox.SelectionStart;
            textBox.Text = String.Format("{0}{1}{2}",
                    textBox.Text.Substring(0, textBox.SelectionStart),
                    Tab,
                    textBox.Text.Substring(textBox.SelectionStart + textBox.SelectionLength, (textBox.Text.Length) - (textBox.SelectionStart + textBox.SelectionLength))
                    );
            e.Handled = true;
            textBox.SelectionStart = selectionStart + Tab.Length;
        }
    } 
}

so that I can access it from various places liek this textBox.KeyDown += TabInsert.textBox_KeyDown;

Is there a way I can do this in XAML?

Answer 1

You can create a Behavior (System.Windows.Interactivity namespace) to easily attach to textboxes that in the OnAttached() override subscribes to the event and does the handling as you do and unsubscribes in OnDetaching().

Something like:

public class TabInsertBehavior : Behavior<TextBox>
{
    /// <summary>
    /// Called after the behavior is attached to an AssociatedObject.
    /// </summary>
    /// <remarks>
    /// Override this to hook up functionality to the AssociatedObject.
    /// </remarks>
    protected override void OnAttached()
    {
        base.OnAttached();
        this.AssociatedObject.KeyDown += textBox_KeyDown;
    }

    private const string Tab = "    ";
    public static void textBox_KeyDown(object sender, KeyEventArgs e)
    {
        TextBox textBox = sender as TextBox;
        if (e.Key == Key.Tab)
        {
            int selectionStart = textBox.SelectionStart;
            textBox.Text = String.Format("{0}{1}{2}",
                    textBox.Text.Substring(0, textBox.SelectionStart),
                    Tab,
                    textBox.Text.Substring(textBox.SelectionStart + textBox.SelectionLength, (textBox.Text.Length) - (textBox.SelectionStart + textBox.SelectionLength))
                    );
            e.Handled = true;
            textBox.SelectionStart = selectionStart + Tab.Length;
        }
    } 

    /// <summary>
    /// Called when the behavior is being detached from its AssociatedObject, but before it has actually occurred.
    /// </summary>
    /// <remarks>
    /// Override this to unhook functionality from the AssociatedObject.
    /// </remarks>
    protected override void OnDetaching()
    {
        base.OnDetaching();
        this.AssociatedObject.KeyDown -= textBox_KeyDown;
    }
}