WPF 高级篇 MVVM 附加属性

Posted 2021-03-21 lonelyxmas

原文:WPF 高级篇 MVVM 附加属性

WPF 特性之一 附加属性 在本文里实现文本框内容的验证

 

  public  class TextBoxHelper:DependencyObject
    {
 
        public static bool GetisOnlyNumber(DependencyObject obj)
        {
            return (bool)obj.GetValue(isOnlyNumberProperty);
        }
 
        public static void SetisOnlyNumber(DependencyObject obj, bool value)
        {
            obj.SetValue(isOnlyNumberProperty, value);
        }
 
        // Using a DependencyProperty as the backing store for isOnlyNumber.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty isOnlyNumberProperty =
            DependencyProperty.RegisterAttached("isOnlyNumber", typeof(bool), typeof(TextBoxHelper), new PropertyMetadata(false,OnIsOnlyNumberChange));
 
        private static void OnIsOnlyNumberChange(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var text = d as TextBox;
            if ((bool)e.NewValue) 
            {
                text.PreviewTextInput += text_PreviewTextInput;
            }else{
                text.PreviewTextInput -= text_PreviewTextInput;
            }
        }
 
        static void text_PreviewTextInput(object sender, System.Windows.Input.TextCompositionEventArgs e)
        {
            e.Handled = IsNotNumber(e.Text);
        }
 
        private static bool IsNotNumber(string content) 
        {
            Regex regex = new Regex("[^0-9]");
            return regex.IsMatch(content);
        }
        
        
    }

引用命名空间

  xmlns:bhx ="clr-namespace:WPF.Behaviors"

        <TextBox bhx:TextBoxHelper.isOnlyNumber="True" HorizontalAlignment="Left" Height="23" Margin="10,131,0,0" TextWrapping="Wrap" Text="{Binding CurrentBook.Pages}" VerticalAlignment="Top" Width="120"/>