C# WPF: Changing color of Text upon Character Detection

Question

I'm writing a Console for users, so that they can write code in it similar to Visual Studio. I was wondering how to change the color of a set of text in a WPF TextBox as soon as the program detects the input of a certain character, such as the /* */ comment tags.

When a user enters a /* tag, the text after the tag should be colored in green and when the users closes the tags, the texts should turn back to white. I tried doing this with the TextChanged method but I don't know how to proceed.

('console' is the TextBox in my Window)

private void console_TextChanged(object sender, TextChangedEventArgs e)
{
      if (e.Changes.Equals("/*"))
      {
             console.Foreground = Brushes.Green;
      }
}

Answer 1

You cannot use TextBox to change some specific portion of color. In this case you need RichTextBox. You use the PreviewTextInput event to get the typed text/char. I have written some logic to make the foreground of the RichTextBox change when typing specific char. I think you can build your logic one top of this code.

 <RichTextBox x:Name="rtb" Width="200" Height="200" PreviewTextInput="rtb_PreviewTextInput"/>

 public partial class MainWindow : Window
{
    string prevText=string.Empty;
    TextPointer start;
    public MainWindow()
    {
        InitializeComponent();            
    }      
    private void rtb_PreviewTextInput(object sender, TextCompositionEventArgs e)
    {
        if (e.Text.Equals("*") && (prevText.Equals("/")))
        {
            start = rtb.CaretPosition;
            TextPointer end = rtb.Document.ContentEnd;
            TextRange range = new TextRange(start, end);
            range.ApplyPropertyValue(RichTextBox.ForegroundProperty, Brushes.Green);
        }
        if (e.Text.Equals("/") && (prevText.Equals("*")))
        {                
            TextPointer end = rtb.CaretPosition; 
            TextRange range = new TextRange(start, end);
            range.ApplyPropertyValue(RichTextBox.ForegroundProperty, Brushes.Red);
        }
        prevText = e.Text;
    }        
}