Capturing tab in Silverlight TextBox

Question

How can I capture a tab entered in a Silverlight TextBox and render 4 spaces (or a tab) in it's place?

I can't figure out how to block the tab navigation.

Answer 1

Here is what I do (similar to Johannes' code):

        private const string Tab = "    ";
    void textBox_KeyDown(object sender, KeyEventArgs e)
    {
        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;
        }
    }

This behaves just how you expect even if you select some text and hit the ol' "Tab" key.

One more thing: I tried having the tab string as "\t", but to no avail. The tab rendered, but was the width of a single space - hence the value for the Tab const being four spaces.

Answer 2

I am not sure how to solve your problem, I hacked together a solution though that seems to work.

Set the KeyDown event as below.

expenses.KeyDown += new KeyEventHandler(expenses_KeyDown);

In that event I put the following code:

void expenses_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.Key == Key.Tab)
            {
                expenses.Text += "    ";
                expenses.Focus();
                expenses.LostFocus += new RoutedEventHandler(expenses_LostFocus);
            }
        }

And then in LostFocus:

void expenses_LostFocus(object sender, RoutedEventArgs e)
        {
            expenses.Focus();
            expenses.Select(expenses.Text.Length - 1, 0);
        }

The last line in LostFocus sets the editing cursor to the end of the text, otherwise, when it gets focus, the cursor position is in the beginning of the textbox