在silverlight一般开发模式中，给文本框添加一些事件是轻而易举的，然而MVVM开发模式中，想要给文本框添加一些事件并非那么容易，因为MVVM模式中，只有ICommand接口，而且也只有Button中才有Command属性，通过ViewModel可以将方法绑定到Button上面，却无法绑定到文本框和其他一些控件。、
Behavior的出现解决了这一难题，下面就来说一下具体的实现方法：
实例一：在用户登录窗口，用户点击Reset按钮后，让用户名输入框自动获取焦点。
首先要先将ViewModel绑定到我们的控件上面，我们一步一步来做，第一步先写Model，下面是Model的代码：
using System;
using System.Net;
using System.Runtime.Serialization;
using System.ComponentModel; namespace BookModel
{
[DataContract]
public class UserModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged; private string userName = String.Empty;
private string passWord = String.Empty; [DataMember]
public string UserName
{
get { return userName; }
set { userName = value; OnPropertyChanged("UserName"); }
} [DataMember]
public string PassWord
{
get { return passWord; }
set { passWord = value; OnPropertyChanged("PassWord"); }
} /// <summary>
/// Call the event PropertyChanged.
/// </summary>
/// <param name="PropertyName"></param>
public void OnPropertyChanged(string PropertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(PropertyName));
}
}
}
}
写完了Model，下一步就是写ViewModel了，在ViewModel中引用Model的命名控件，下面是ViewModel的代码，例子比较简单，就不多解释了。
using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using BookModel;
using System.Windows.Browser; namespace BookViewModel
{
public class VM_User
{
/// <summary>
/// In the Constructors create the instance of User.
/// </summary>
public VM_User()
{
user = new UserModel();
user.UserName = "Jack";
} public UserModel user { get; set; }
public LoginCommand Login
{
get { return new LoginCommand(); }
}
public ResteCommand Reset
{
get { return new ResteCommand(); }
}
} /// <summary>
/// Login Button's method
/// </summary>
public class LoginCommand:ICommand
{
public bool CanExecute(object parameter)
{
return true;
} public void Execute(object parameter)
{
VM_User VMUser = parameter as VM_User;
if (VMUser.user.UserName.Equals("admin") && VMUser.user.PassWord.Equals(""))
{
MessageBox.Show("Login success!", "System Info", MessageBoxButton.OK);
}
else
{
MessageBox.Show("Login failed!", "System Info", MessageBoxButton.OK);
}
} public event EventHandler CanExecuteChanged;
} /// <summary>
/// Reset buttom's method
/// </summary>
public class ResteCommand : ICommand
{
public bool CanExecute(object parameter)
{
return true;
} public void Execute(object parameter)
{
VM_User VMUser = parameter as VM_User;
VMUser.user.UserName = "";
VMUser.user.PassWord = "";
}
public event EventHandler CanExecuteChanged;
}
}
这里就不连接数据库了，那样代码量太大，也不方便大家查看。这里只做一个简单的验证，至此MVVM中的M和VM就都建好了，下面写前端的显示层，添加两个TextBlock和两个TextBox，两个按钮。用作登录用，分别为用户名，密码，登录和重置。
下面是绑定代码：
<UserControl x:Class="BookLibrary.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:BookViewModel;assembly=BookViewModel"
mc:Ignorable="d"
d:DesignHeight="" d:DesignWidth=""
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"> <UserControl.Resources>
<local:VM_User x:Key="User" />
</UserControl.Resources>
<Grid x:Name="LayoutRoot" Background="White" DataContext="{Binding Source={StaticResource User}}" Loaded="LayoutRoot_Loaded">
<telerik:RadBusyIndicator Name="BusyIndicator">
<Border>
<Border.Background>
<LinearGradientBrush EndPoint="0.5 1" StartPoint="0.5 0">
<GradientStop Color="#0369a9" Offset="" />
<GradientStop Color="#046daf" Offset="0.5" />
<GradientStop Color="#2fa2e5" Offset="" />
</LinearGradientBrush>
</Border.Background>
<Border VerticalAlignment="Center" HorizontalAlignment="Center">
<Border.Effect>
<DropShadowEffect BlurRadius="" Opacity="0.4"/>
</Border.Effect>
<Border.Background>
<RadialGradientBrush>
<GradientStop Color="#0B7AC1" Offset="" />
<GradientStop Color="#1182c7" Offset="" />
</RadialGradientBrush>
</Border.Background>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height=""/>
<RowDefinition Height=""/>
<RowDefinition Height=""/>
<RowDefinition Height=""/>
<RowDefinition Height=""/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width=""/>
<ColumnDefinition Width=""/>
<ColumnDefinition Width=""/>
<ColumnDefinition Width=""/>
</Grid.ColumnDefinitions>
<TextBlock VerticalAlignment="Center" HorizontalAlignment="Left"
Grid.Row="" Grid.Column="" Margin="20,0,0,0" FontWeight="Bold"
Text="School System |" FontSize="" Foreground="White"/>
<TextBlock Grid.Row="" Grid.Column="" HorizontalAlignment="Left"
VerticalAlignment="Center" Text="User Login" FontSize=""
Foreground="#b4e6ec"/>
<Image Source="Images/LoginPicture.png" Grid.Row="" Grid.Column="" Grid.RowSpan="" />
<TextBlock FontSize="" Grid.Row="" Grid.Column="" Text="UserName:"
Foreground="White" VerticalAlignment="Center" HorizontalAlignment="Left" />
<TextBlock FontSize="" Grid.Row="" Grid.Column="" Text="PassWord:"
Foreground="White" VerticalAlignment="Center" HorizontalAlignment="Left" />
<TextBox Name="txtName" Text="{Binding user.UserName,Mode=TwoWay}" HorizontalAlignment="Left" FontSize="" Grid.Row="" Grid.Column="" Width="" Height="" />
<PasswordBox Password="{Binding user.PassWord,Mode=TwoWay}" HorizontalAlignment="Left" Grid.Row="" Grid.Column="" Width="" Height="" />
<Button Command="{Binding Login}" CommandParameter="{Binding}" HorizontalAlignment="Left" Width="" Height="" Grid.Row="" Grid.Column="" Content="Login" Click="Button_Click_1" />
<Button Command="{Binding Reset}" CommandParameter="{Binding}" HorizontalAlignment="Left" Width="" Height="" Grid.Row="" Grid.Column="" Content="Reset" Click="Button_Click" />
<CheckBox HorizontalAlignment="Left" VerticalAlignment="Top" Margin="0,10,0,0" Grid.Row="" Grid.Column="" Content="Save State" Foreground="White" /> </Grid>
</Border>
</Border>
</telerik:RadBusyIndicator> </Grid>
</UserControl>
这个时候，就实现登录和重置功能了，但是重置的时候用户名文本框并不会获得焦点，下面我们来讲实现方法：
第一种方法：TargetedTriggerAction绑定
先写一个类，叫做TextBoxGetFocusBahavior，代码如下：
using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Windows.Interactivity; namespace BookLibrary
{
public class TextBoxGetFocusBahavior:TargetedTriggerAction<TextBox>
{
public void GotFocusAction()
{ }
protected override void Invoke(object parameter)
{
TextBox targetTextBox = Target;
targetTextBox.SelectAll();
}
}
}
然后在前台绑定，绑定方法如下：
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
<TextBox Height="" Name="textBox" HorizontalAlignment="Left" Margin="36,28,0,0" VerticalAlignment="Top" Width="">
<i:Interaction.Triggers>
<i:EventTrigger EventName="GotFocus">
<local:TextBoxGetFocusBahavior TargetName="textBox" />
</i:EventTrigger>
</i:Interaction.Triggers> </TextBox>
注意我标红的地方，就是要引入命名空间。
第二种方法Behavior方法，和上面基本一样，不过我感觉这种方法比较灵活，推荐使用这种方法。新加一个类，AutoSetFocusBehavior，代码如下：
using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Windows.Interactivity; namespace BookLibrary
{
public class AutoSetFocusBehavior:Behavior<TextBox>
{
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.TextChanged += OnTextChanged;
} public void OnTextChanged(object sender, EventArgs e)
{
if(AssociatedObject.Text.Equals(""))
AssociatedObject.Focus();
}
}
}
这里前端绑定方法为：
<TextBox Text="{Binding user.UserName}" x:Name="txtName" Height="" HorizontalAlignment="Left" Margin="36,76,0,0" VerticalAlignment="Top" Width="">
<i:Interaction.Behaviors>
<local:AutoSetFocusBehavior />
</i:Interaction.Behaviors>
</TextBox>
注意，同样要引入上面的命名空间。
其实，说了这么多，就是给TextBox加了个OnTextChanged事件，当内容被清空时，判断内容是否为空，为空则设置焦点。
希望这篇文章能给大家一点帮助。不足之处，还请赐教。