TextBoxInputMask避免使用空格

Question

我正在尝试构建如下所示的IP地址输入框掩码：

我不喜欢的是数字之间的空格。我的问题是，如何防止数字之间的空格并强制用户写一个数字而不是左边的空格。

行为类

public class TextBoxInputMaskBehavior : Behavior<TextBox>
    {
        public MaskedTextProvider Provider { get; private set; }

        protected override void OnAttached()
        {
            base.OnAttached();
            AssociatedObject.Loaded += AssociatedObjectLoaded;
            AssociatedObject.PreviewTextInput += AssociatedObjectPreviewTextInput;
            AssociatedObject.PreviewKeyDown += AssociatedObjectPreviewKeyDown;

            DataObject.AddPastingHandler(AssociatedObject, Pasting);
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();
            AssociatedObject.Loaded -= AssociatedObjectLoaded;
            AssociatedObject.PreviewTextInput -= AssociatedObjectPreviewTextInput;
            AssociatedObject.PreviewKeyDown -= AssociatedObjectPreviewKeyDown;

            DataObject.RemovePastingHandler(AssociatedObject, Pasting);
        }

        /*
        Mask Character  Accepts  Required?  
        0  Digit (0-9)  Required  
        9  Digit (0-9) or space  Optional  
        #  Digit (0-9) or space  Required  
        L  Letter (a-z, A-Z)  Required  
        ?  Letter (a-z, A-Z)  Optional  
        &  Any character  Required  
        C  Any character  Optional  
        A  Alphanumeric (0-9, a-z, A-Z)  Required  
        a  Alphanumeric (0-9, a-z, A-Z)  Optional  
           Space separator  Required 
        .  Decimal separator  Required  
        ,  Group (thousands) separator  Required  
        :  Time separator  Required  
        /  Date separator  Required  
        $  Currency symbol  Required  

        In addition, the following characters have special meaning:

        Mask Character  Meaning  
        <  All subsequent characters are converted to lower case  
        >  All subsequent characters are converted to upper case  
        |  Terminates a previous < or >  
        \  Escape: treat the next character in the mask as literal text rather than a mask symbol  

        */

        private void AssociatedObjectLoaded(object sender, RoutedEventArgs e)
        {
            Provider = new MaskedTextProvider(InputMask, CultureInfo.CurrentCulture);
            Provider.Set(AssociatedObject.Text);
            Provider.PromptChar = PromptChar;
            AssociatedObject.Text = Provider.ToDisplayString();

            //seems the only way that the text is formatted correct, when source is updated
            var textProp = DependencyPropertyDescriptor.FromProperty(TextBox.TextProperty, typeof (TextBox));
            if (textProp != null)
            {
                textProp.AddValueChanged(AssociatedObject, (s, args) => UpdateText());
            }
        }

        private void AssociatedObjectPreviewTextInput(object sender, TextCompositionEventArgs e)
        {
            TreatSelectedText();

            var position = GetNextCharacterPosition(AssociatedObject.SelectionStart);

            if (Keyboard.IsKeyToggled(Key.Insert))
            {
                if (Provider.Replace(e.Text, position))
                    position++;
            }
            else
            {
                if (Provider.InsertAt(e.Text, position))
                    position++;
            }

            position = GetNextCharacterPosition(position);

            RefreshText(position);

            e.Handled = true;
        }

        private void AssociatedObjectPreviewKeyDown(object sender, KeyEventArgs e)
        {
            if (e.Key == Key.Space) //handle the space
            {
                TreatSelectedText();

                var position = GetNextCharacterPosition(AssociatedObject.SelectionStart);

                if (Provider.InsertAt(" ", position))
                    RefreshText(position);

                e.Handled = true;
            }

            if (e.Key == Key.Back) //handle the back space
            {
                if (TreatSelectedText())
                {
                    RefreshText(AssociatedObject.SelectionStart);
                }
                else
                {
                    if (AssociatedObject.SelectionStart != 0)
                    {
                        if (Provider.RemoveAt(AssociatedObject.SelectionStart - 1))
                            RefreshText(AssociatedObject.SelectionStart - 1);
                    }
                }

                e.Handled = true;
            }

            if (e.Key == Key.Delete) //handle the delete key
            {
                //treat selected text
                if (TreatSelectedText())
                {
                    RefreshText(AssociatedObject.SelectionStart);
                }
                else
                {
                    if (Provider.RemoveAt(AssociatedObject.SelectionStart))
                        RefreshText(AssociatedObject.SelectionStart);
                }

                e.Handled = true;
            }
        }

        /// <summary>
        ///     Pasting prüft ob korrekte Daten reingepastet werden
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Pasting(object sender, DataObjectPastingEventArgs e)
        {
            if (e.DataObject.GetDataPresent(typeof (string)))
            {
                var pastedText = (string) e.DataObject.GetData(typeof (string));

                TreatSelectedText();

                var position = GetNextCharacterPosition(AssociatedObject.SelectionStart);

                if (Provider.InsertAt(pastedText, position))
                {
                    RefreshText(position);
                }
            }

            e.CancelCommand();
        }

        private void UpdateText()
        {
            //check Provider.Text + TextBox.Text
            if (Provider.ToDisplayString().Equals(AssociatedObject.Text))
                return;

            //use provider to format
            var success = Provider.Set(AssociatedObject.Text);

            //ui and mvvm/codebehind should be in sync
            SetText(success ? Provider.ToDisplayString() : AssociatedObject.Text);
        }

        /// <summary>
        ///     Falls eine Textauswahl vorliegt wird diese entsprechend behandelt.
        /// </summary>
        /// <returns>true Textauswahl behandelt wurde, ansonsten falls </returns>
        private bool TreatSelectedText()
        {
            if (AssociatedObject.SelectionLength > 0)
            {
                return Provider.RemoveAt(AssociatedObject.SelectionStart,
                    AssociatedObject.SelectionStart + AssociatedObject.SelectionLength - 1);
            }
            return false;
        }

        private void RefreshText(int position)
        {
            SetText(Provider.ToDisplayString());
            AssociatedObject.SelectionStart = position;
        }

        private void SetText(string text)
        {
            AssociatedObject.Text = string.IsNullOrWhiteSpace(text) ? string.Empty : text;
        }

        private int GetNextCharacterPosition(int startPosition)
        {
            var position = Provider.FindEditPositionFrom(startPosition, true);

            if (position == -1)
                return startPosition;
            return position;
        }

        #region DependencyProperties

        public static readonly DependencyProperty InputMaskProperty =
            DependencyProperty.Register("InputMask", typeof (string), typeof (TextBoxInputMaskBehavior), null);

        public string InputMask
        {
            get { return (string) GetValue(InputMaskProperty); }
            set { SetValue(InputMaskProperty, value); }
        }

        public static readonly DependencyProperty PromptCharProperty =
            DependencyProperty.Register("PromptChar", typeof (char), typeof (TextBoxInputMaskBehavior),
                new PropertyMetadata('_'));

        public char PromptChar
        {
            get { return (char) GetValue(PromptCharProperty); }
            set { SetValue(PromptCharProperty, value); }
        }

        #endregion
    }

和xaml

<TextBox VerticalContentAlignment="Center" HorizontalContentAlignment="Center" Grid.Row="6" Grid.Column="1" FontSize="22" >
            <i:Interaction.Behaviors>
                <behaviors:TextBoxInputMaskBehavior InputMask="{StaticResource InputMaskIp}" PromptChar="_" />
            </i:Interaction.Behaviors>
        </TextBox>