WPF TextBox 仅允许输入数字

因为在 IValueConverter 实现中，当文本不能转换为目标类型时返回 DependencyProperty.UnsetValue ，Validation.GetHasError 返回 true ，为何要绕一个圈让用户输入不能转换的文本，然后再获取错误状态呢？不如直接不让用户输入错误文本，于是写了一个 Behavior 派生类：

 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;
 using System.Windows.Interactivity;

 namespace WpfApplication6
 {
     public class OnlyDigitalBehavior : Behavior<TextBox>
     {
         public Type DigitalType
         {
             get { return (Type)GetValue(DigitalTypeProperty); }
             set { SetValue(DigitalTypeProperty, value); }
         }

         public static readonly DependencyProperty DigitalTypeProperty =
             DependencyProperty.Register("DigitalType", typeof(Type), typeof(OnlyDigitalBehavior), new PropertyMetadata());

         protected override void OnAttached()
         {
             base.OnAttached();
             this.AssociatedObject.PreviewTextInput += AssociatedObject_PreviewTextInput;
             DataObject.AddPastingHandler(this.AssociatedObject, AssociatedObject_Pasting);
             InputMethod.SetIsInputMethodEnabled(this.AssociatedObject, false);
         }

         private void AssociatedObject_Pasting(object sender, DataObjectPastingEventArgs e)
         {
             e.CancelCommand();
         }

         protected override void OnDetaching()
         {
             base.OnDetaching();
             this.AssociatedObject.PreviewTextInput -= AssociatedObject_PreviewTextInput;
             DataObject.RemovePastingHandler(this.AssociatedObject, AssociatedObject_Pasting);
         }

         private void AssociatedObject_PreviewTextInput(object sender, System.Windows.Input.TextCompositionEventArgs e)
         {
             TextBox textBox = sender as TextBox;
             Type digitalType = this.DigitalType;
             if (textBox == null)
             {
                 return;
             }
             if (digitalType == typeof(Int16))
             {
                 Int16 i = ;
                 if (Int16.TryParse(textBox.Text + e.Text, out i))
                 {
                     return;
                 }
             }
             else if (digitalType == typeof(Int32))
             {
                 Int32 i = ;
                 if (Int32.TryParse(textBox.Text + e.Text, out i))
                 {
                     return;
                 }
             }
             else if (digitalType == typeof(Int64))
             {
                 Int64 i = ;
                 if (Int64.TryParse(textBox.Text + e.Text, out i))
                 {
                     return;
                 }
             }
             else if (digitalType == typeof(double))
             {
                 double d = ;
                 if (double.TryParse(textBox.Text + e.Text, out d))
                 {
                     return;
                 }
             }
             else if (digitalType == typeof(decimal))
             {
                 decimal d = ;
                 if (decimal.TryParse(textBox.Text + e.Text, out d))
                 {
                     return;
                 }
             }
             e.Handled = true;
         }
     }
 }

InputMethod.SetIsInputMethodEnabled(this.AssociatedObject, false); 作用是屏蔽输入法。

以下是测试View：

 <Window x:Class="WpfApplication6.MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
         xmlns:local="clr-namespace:WpfApplication6"
         xmlns:sys="clr-namespace:System;assembly=mscorlib"
         Title="MainWindow" Height="350" Width="525">
     <StackPanel>
         <TextBlock Margin="3">Int16</TextBlock>
         <TextBox Margin="3">
             <i:Interaction.Behaviors>
                 <local:OnlyDigitalBehavior DigitalType="{x:Type sys:Int16}" />
             </i:Interaction.Behaviors>
         </TextBox>
         <TextBlock Margin="3">Int32</TextBlock>
         <TextBox Margin="3">
             <i:Interaction.Behaviors>
                 <local:OnlyDigitalBehavior DigitalType="{x:Type sys:Int32}" />
             </i:Interaction.Behaviors>
         </TextBox>
         <TextBlock Margin="3">Int64</TextBlock>
         <TextBox Margin="3">
             <i:Interaction.Behaviors>
                 <local:OnlyDigitalBehavior DigitalType="{x:Type sys:Int64}" />
             </i:Interaction.Behaviors>
         </TextBox>
         <TextBlock Margin="3">Double</TextBlock>
         <TextBox Margin="3">
             <i:Interaction.Behaviors>
                 <local:OnlyDigitalBehavior DigitalType="{x:Type sys:Double}" />
             </i:Interaction.Behaviors>
         </TextBox>
         <TextBlock Margin="3">Decimal</TextBlock>
         <TextBox Margin="3">
             <i:Interaction.Behaviors>
                 <local:OnlyDigitalBehavior DigitalType="{x:Type sys:Decimal}" />
             </i:Interaction.Behaviors>
         </TextBox>
     </StackPanel>
 </Window>

如果大家有更好的实现方法欢迎赐教！

再来一个支持粘贴的：

 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;
 using System.Windows.Interactivity;

 namespace WpfApplication6
 {
     public class OnlyDigitalBehavior : Behavior<TextBox>
     {
         private string lastRight = null;

         public Type DigitalType
         {
             get { return (Type)GetValue(DigitalTypeProperty); }
             set { SetValue(DigitalTypeProperty, value); }
         }

         public static readonly DependencyProperty DigitalTypeProperty =
             DependencyProperty.Register("DigitalType", typeof(Type), typeof(OnlyDigitalBehavior), new PropertyMetadata());

         protected override void OnAttached()
         {
             base.OnAttached();
             this.AssociatedObject.TextChanged += AssociatedObject_TextChanged;
             InputMethod.SetIsInputMethodEnabled(this.AssociatedObject, false);
         }

         protected override void OnDetaching()
         {
             base.OnDetaching();
             this.AssociatedObject.TextChanged -= AssociatedObject_TextChanged;
         }

         private void AssociatedObject_TextChanged(object sender, TextChangedEventArgs e)
         {
             TextBox textBox = sender as TextBox;
             Type digitalType = this.DigitalType;
             if (textBox == null)
             {
                 return;
             }
             if ((IsDigital(digitalType,textBox.Text) || string.IsNullOrEmpty(textBox.Text)) && lastRight != textBox.Text)
             {
                 lastRight = textBox.Text;
             }
             else if (textBox.Text != lastRight)
             {
                 textBox.Text = lastRight;
                 textBox.SelectionStart = textBox.Text.Length;
             }
         }

         private bool IsDigital(Type targetType,string digitalString)
         {
             if (targetType == typeof(Int16))
             {
                 Int16 i = ;
                 if (Int16.TryParse(digitalString, out i))
                 {
                     return true;
                 }
             }
             else if (targetType == typeof(Int32))
             {
                 Int32 i = ;
                 if (Int32.TryParse(digitalString, out i))
                 {
                     return true;
                 }
             }
             else if (targetType == typeof(Int64))
             {
                 Int64 i = ;
                 if (Int64.TryParse(digitalString, out i))
                 {
                     return true;
                 }
             }
             else if (targetType == typeof(double))
             {
                 double d = ;
                 if (double.TryParse(digitalString, out d))
                 {
                     return true;
                 }
             }
             else if (targetType == typeof(decimal))
             {
                 decimal d = ;
                 if (decimal.TryParse(digitalString, out d))
                 {
                     return true;
                 }
             }
             return false;
         }
     }
 }