private void SourceCodeBox_TextChanged(object sender, TextChangedEventArgs e)
{
var document = SourceCodeBox.Document;
var code = new TextRange(document.ContentStart, document.ContentEnd).Text;
var linesCount = code.Lines();
if (LineNumbersBox.Text.Lines() == linesCount) return;
LineNumbersBox.Text = "";
for (var i = 0; i < linesCount - 1; i++)
{
LineNumbersBox.Text += i + 1 + "\n";
}
}