mask.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace WpfTest
{
    public enum MaskType
    {
        None = 0,
        Isic = 1,
    }

    public partial class TextBoxExt
    {
        #region Dependency Property
        public static readonly DependencyProperty MaskProperty = DependencyProperty.RegisterAttached("Mask",
            typeof(MaskType), typeof(TextBoxExt), new FrameworkPropertyMetadata(MaskChangedCallback));

        public static MaskType GetMask(DependencyObject obj)
        {
            return (MaskType)obj.GetValue(MaskProperty);
        }

        public static void SetMask(DependencyObject obj, MaskType value)
        {
            obj.SetValue(MaskProperty, value);
        }

        private static void MaskChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var oldVal = e.OldValue as TextBox;
            if (oldVal != null)
            {
                oldVal.PreviewTextInput -= TextBox_PreviewTextInput;
                oldVal.PreviewKeyDown -= TextBox_PreviewKeyDown;

                DataObject.RemovePastingHandler(oldVal, (DataObjectPastingEventHandler)TextBoxPastingEventHandler);
            }

            var textBox = d as TextBox;
            if (textBox == null)
                return;

            if ((MaskType)e.NewValue != MaskType.None)
            {
                textBox.PreviewTextInput += TextBox_PreviewTextInput;
                textBox.PreviewKeyDown += TextBox_PreviewKeyDown;
                DataObject.AddPastingHandler(textBox, (DataObjectPastingEventHandler)TextBoxPastingEventHandler);
            }
        }

        #endregion

        private static void TextBox_PreviewKeyDown(object sender, KeyEventArgs e)
        {
            var textBox = sender as TextBox;
            if (textBox == null) return;
            var caret = textBox.CaretIndex;
            var oldText = textBox.Text;

            if (e.Key == Key.Back)
            {
                if (oldText.Length == 0 || caret == 0)
                {
                    e.Handled = true;
                    textBox.Text = oldText;
                    return;
                }

                if (textBox.SelectionLength > 0)
                {
                    oldText = oldText.Remove(textBox.SelectionStart, textBox.SelectionLength);
                    caret = textBox.SelectionStart;

                    textBox.Text = FormatValue(GetMask(textBox), oldText);
                    textBox.CaretIndex = FixCaretIndex(GetMask(textBox), caret, oldText, true, false);
                    e.Handled = true;
                }

                var newText = oldText.Remove(caret-1, 1);
                caret -= 1;

                if (newText.Any() && caret > 0 && newText[caret-1] == ' ')
                {
                    newText = newText.Remove(caret - 1, 1);
                    caret -= 1;
                }
                textBox.Text = FormatValue(GetMask(textBox), newText);
                textBox.CaretIndex = FixCaretIndex(GetMask(textBox), caret, newText, true, false);
                e.Handled = true;
            }
            else if (e.Key == Key.Delete)
            {
                if (oldText.Length == 0 || oldText.Length == caret)
                {
                    e.Handled = true;
                    textBox.Text = oldText;
                    return;
                }

                if (textBox.SelectionLength > 0)
                {
                    oldText = oldText.Remove(textBox.SelectionStart, textBox.SelectionLength);
                    caret = textBox.SelectionStart;

                    textBox.Text = FormatValue(GetMask(textBox), oldText);
                    textBox.CaretIndex = FixCaretIndex(GetMask(textBox), caret, oldText, false, true);
                    e.Handled = true;
                }

                var newText = oldText.Remove(caret, 1);

                if (caret < newText.Length && newText[caret] == ' ')
                {
                    newText = newText.Remove(caret, 1);
                }
                textBox.Text = FormatValue(GetMask(textBox), newText);
                textBox.CaretIndex = FixCaretIndex(GetMask(textBox), caret, newText, false, true);
                e.Handled = true;
            }
            else if (e.Key == Key.Right)
            {
                caret += 1;
                if (caret < textBox.Text.Length && textBox.Text[caret] == ' ')
                {
                    caret += 1;
                }

                textBox.CaretIndex = caret;
                e.Handled = true;
            }
            else if (e.Key == Key.Left)
            {
                caret = Math.Max( caret - 1, 0);
                if (caret > 0 && textBox.Text[caret-1] == ' ')
                {
                    caret -= 1;
                }

                textBox.CaretIndex = caret;
                e.Handled = true;
            }

            else if (e.Key == Key.Space)
            {
                e.Handled = true;
            }
        }

        private static void TextBoxPastingEventHandler(object sender, DataObjectPastingEventArgs e)
        {
            TextBox tb = (sender as TextBox);
            var text = tb.Text;
            var caret = tb.CaretIndex;
            string clipboard = e.DataObject.GetData(typeof(string)) as string;


            if (tb.SelectionLength != 0)
            {
                text = text.Remove(tb.SelectionStart, tb.SelectionLength);
                caret = tb.SelectionStart;
            }

            text = text.Insert(caret, clipboard);
            caret += clipboard.Length;

            tb.Text = FormatValue(GetMask(tb), text);
            tb.CaretIndex = tb.Text.Length;
            e.CancelCommand();
            e.Handled = true;
        }

        private static void TextBox_PreviewTextInput(object sender, TextCompositionEventArgs e)
        {
            var textbox = sender as TextBox;
            if (textbox == null) return;
            e.Handled = false;
            var caretIndex = textbox.CaretIndex;
            var text = textbox.Text;
            if (textbox.SelectionLength != 0)
            {
                text = text.Remove(textbox.SelectionStart, textbox.SelectionLength);
            }
            var newText = FormatValue(GetMask(textbox), text.Insert(caretIndex, e.Text));
            textbox.Text = newText;

            caretIndex += 1;

            textbox.CaretIndex = FixCaretIndex(GetMask(textbox), caretIndex, newText, true, false);
            e.Handled = true;
        }

        private static int FixCaretIndex(MaskType mask, int caretIndex, string text, bool moveForward = true, bool moveBackward = true)
        {
            if (moveBackward && caretIndex < text.Length && text[caretIndex] == ' ')
            {
                caretIndex -= 1;
            }
            else if (moveForward && caretIndex < text.Length && caretIndex > 0 && text[caretIndex - 1] == ' ')
            {
                caretIndex += 1;
            }

            if (caretIndex >= text.Length)
            {
                caretIndex = text.Length;
            }

            return caretIndex;
        }

        private static string FormatValue(MaskType mask, string value)
        {
            if (mask != MaskType.Isic) return String.Empty;

            var sbuilder = new StringBuilder();
            var index = 0;

            value = value.RemoveWhitespace().ToUpper();

            if (value.Length > 11)
                value = value.Substring(0, 11);

            foreach (var ch in value)
            {
                if (ch != ' ' && (index == 1 || index == 4 || index == 7 || index == 10))
                {
                    sbuilder.Append(' ');
                }

                sbuilder.Append(ch);
                index++;
            }

            return sbuilder.ToString();
        }
    }

    public static class Extensions
    {
        public static string RemoveWhitespace(this string input)
        {
            return new string(input.ToCharArray()
                .Where(c => !Char.IsWhiteSpace(c))
                .ToArray());
        }
    }
}