先回忆一下aspx中的处理:

在aspx中，可以直接在后台定义一个变量，然后前台就可以用<%=xxx%>来将其"绑定"html控件上，比如下面这样，实在是很方便:

代码

using System;

namespace WebApplication1
{
     public partial class _Default : System.Web.UI.Page
    {
         protected string _Test = DateTime.Now.ToString();

         protected void Page_Load( object sender, EventArgs e)
        {

        }
    }
}

代码

<% @ Page Language = " C# " AutoEventWireup = " true " CodeBehind = " Default.aspx.cs " Inherits = " WebApplication1._Default " %>

<! DOCTYPE html PUBLIC " -//W3C//DTD XHTML 1.0 Transitional//EN " " http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd " >

< html xmlns = " http://www.w3.org/1999/xhtml " >
< head runat = " server " >
     < title ></ title >
</ head >
< body >
     < form id = " form1 " runat = " server " >
     < input id = " Text1 " type = " text " value = " <%=_Test %> " />
     </ form >
</ body >
</ html >

但到了Silverlight中，要想直接将后台的变量绑定到某个控件上却是行不通的，通常我们得先定义一个类，然后在类里定义属性，才能把类实例的属性绑定到控件:

简单绑定:

代码

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Shapes;

namespace BindVariable
{
     public partial class MainPage : UserControl
    {

         public class MyClass { public string Test { set ; get ; } }

         public MyClass TestClass;

         public MainPage()
        {
            InitializeComponent();
            TestClass = new MyClass();
            TestClass.Test = " 123 " ;
             this .textBox1.DataContext = TestClass;
        }

    }
}

     < StackPanel >
       < TextBox x:Name ="textBox1" Text =" {Binding Test} " />
     </ StackPanel >

这样就完成了功能最简单的绑定，还想玩得更深入一点，比如实现OneWay,TwoWay方式的绑定(不清楚绑定模式的朋友，建议先参看http://www.cnblogs.com/yjmyzz/archive/2009/11/09/1599058.html)，这样仍然不行，比如我们稍微把刚才的代码改一下:

"自动更新"的绑定:

代码

运行后，点击按钮，发现textbox1中的内容并无变化，原因是：要想实现源与目标的数据自动关联更新，MyClass得实现INotifyPropertyChanged接口，我们把MyClass的定义改成下面这样:

代码

public class MyClass:INotifyPropertyChanged {
     public event PropertyChangedEventHandler PropertyChanged;

     private string _test;

     public string Test
    {
         set {
        _test = value;
         if (PropertyChanged != null )
        {
            PropertyChanged( this , new PropertyChangedEventArgs( " Test " ));
        }
    }
         get { return _test; }
    }
}

再次运行，发现点击按钮后，textbox1的内容变成了456，达到预期的效果了.
绑定集合(数据集):

很多应用场合中，数据来源不仅只有一个实例(或一条记录)--比如从数据库中检索的记录，这时如果想绑定数据并实现自动更新，应使用集合绑定(类似于aspx中的DataSet或DataTable)。要注意的是，使用集合绑定并实现自动更新，除了要实现 INotifyPropertyChanged 外，还要实现 INotifyCollectionChanged。幸好.net框架已经有一个ObservableCollection<T> 类，该类具有 INotifyCollectionChanged 和 INotifyPropertyChanged 的内置实现。可以直接拿来用:

代码

using System.Collections.ObjectModel;
using System.Windows;
using System.Windows.Controls;

namespace BindVariable
{
     public partial class MainPage : UserControl
    {

         public class MyClass { public string Test { set ; get ; } }

        ObservableCollection < MyClass > oc = new ObservableCollection < MyClass > (){
             new MyClass() { Test = " 1 " },
             new MyClass() { Test = " 2 " },
             new MyClass() { Test = " 3 " }
        };

         public MainPage()
        {
            InitializeComponent();
             this .lst.ItemsSource = oc;
        }

         private void btnChange_Click( object sender, RoutedEventArgs e)
        {
            oc.Add( new MyClass() { Test = " 4 " });
        }
    }
}

IValueConverter:

上述的绑定，都是将数据原封不动的绑定并显示，如果我们希望在绑定时，能对数据的输出做一些变化，比如：代表性别的"1,0"输出时希望变成"男,女"，该怎么办呢？(silverlight中可不允许象aspx那样用<%# Eval("Sex").ToString()=="1"?"男":"女"%>来搞定) 答案:IValueConverter

代码

using System;
using System.Collections.ObjectModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;

namespace BindVariable
{
     public partial class MainPage : UserControl
    {

         public class MyClass
        {
             public string Test { set ; get ; }
             public bool Sex { set ; get ; }
        }

        ObservableCollection < MyClass > oc = new ObservableCollection < MyClass > (){
             new MyClass() { Test = " 1 " ,Sex = true },
             new MyClass() { Test = " 2 " ,Sex = false },
             new MyClass() { Test = " 3 " ,Sex = true }
        };

         public MainPage()
        {
            InitializeComponent();
             this .lst.ItemsSource = oc;
        }

         private void btnChange_Click( object sender, RoutedEventArgs e)
        {
            oc.Add( new MyClass() { Test = " 4 " , Sex = false });
        }

    }

     /// <summary>
     /// bool转化为性别字符串
     /// </summary>
     public class BoolToSexConverter : IValueConverter
    {

         public object Convert( object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
             try
            {
                 return (( bool )value) ? " 男 " : " 女 " ;
            }
             catch
            {
                 return " ? " ;
            }

        }

         // 只有TwoWay模式下，才需要实现该方法，否则可以不用理
         public object ConvertBack( object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
             throw new NotImplementedException();
        }
    }
}

代码

< UserControl
     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"
    x:Class ="BindVariable.MainPage"
    xmlns:local ="clr-namespace:BindVariable"
    >
     < StackPanel Orientation ="Vertical" >
         < StackPanel.Resources >
             < local:BoolToSexConverter x:Key ="Bool2Sex" ></ local:BoolToSexConverter >
         </ StackPanel.Resources >
         < ListBox x:Name ="lst" >
             < ListBox.ItemTemplate >
                 < DataTemplate >
                     < StackPanel Orientation ="Horizontal" >
                         < TextBlock Text =" {Binding Test} " ></ TextBlock >
                         < TextBlock Text ="，" ></ TextBlock >
                         < TextBlock Text =" {Binding Path=Sex, Converter={StaticResource Bool2Sex}} " ></ TextBlock >
                     </ StackPanel >
                 </ DataTemplate >
             </ ListBox.ItemTemplate >
         </ ListBox >
         < Button x:Name ="btnChange" Content ="Change Test" Click ="btnChange_Click" ></ Button >
     </ StackPanel >
</ UserControl >

也许您注意到了IValueConverter的Convert方法中，还能传入参数！我们可以利用这个玩点小花样，比如界面上有三个矩形，其中"矩形2的宽度"等于"矩形1的宽度"+"一个任意指定的固定值"，矩形3的宽度矩形1与矩形2的宽度总和，不允用 rect2.width = rect1.width，rect3.width = rect2.width + rect1.width 来处理:) 您会怎么做呢？

代码

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;

namespace BindVariable
{
     public partial class MainPage : UserControl
    {
         public MainPage()
        {
            InitializeComponent();
        }
    }

     public class DoubleAddConverter : IValueConverter
    {

         public object Convert( object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
             try
            {
                 return double .Parse(value.ToString()) + double .Parse(parameter.ToString());
            }
             catch
            {
                 return 50.0 ;
            }

        }

         // 只有TwoWay模式下，才需要实现该方法，否则可以不用理
         public object ConvertBack( object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
             throw new NotImplementedException();
        }
    }

     public class FrameworkElementAddConverter : IValueConverter
    {

         public object Convert( object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
             try
            {
                 return double .Parse(value.ToString()) + ((App.Current.RootVisual as FrameworkElement).FindName(parameter.ToString()) as FrameworkElement).Width;
            }
             catch
            {
                 return 50.0 ;
            }

        }

         // 只有TwoWay模式下，才需要实现该方法，否则可以不用理
         public object ConvertBack( object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
             throw new NotImplementedException();
        }
    }

}

代码

< UserControl
     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"
    x:Class ="BindVariable.MainPage"
    xmlns:local ="clr-namespace:BindVariable"
    >
     < StackPanel Orientation ="Vertical" HorizontalAlignment ="Left" >
         < StackPanel.Resources >
             < local:DoubleAddConverter x:Key ="DoubleAdd" ></ local:DoubleAddConverter >
             < local:FrameworkElementAddConverter x:Key ="FEAdd" ></ local:FrameworkElementAddConverter >
         </ StackPanel.Resources >

         < Rectangle x:Name ="rect1" Width ="100" Height ="50" Fill ="Gray" HorizontalAlignment ="Left" ></ Rectangle >

         < Rectangle x:Name ="rect2" Height ="50" Width =" {Binding Width, Converter={StaticResource DoubleAdd}, ConverterParameter=100, ElementName=rect1, Mode=OneWay} "   Fill ="Red" HorizontalAlignment ="Left" ></ Rectangle >

         < Rectangle x:Name ="rect3" Height ="50"   Fill ="Blue" Width =" {Binding Width, Converter={StaticResource FEAdd}, ConverterParameter=rect2, ElementName=rect1, Mode=OneWay} " ></ Rectangle >
     </ StackPanel >
</ UserControl >

这样就搞定了，也许有人会问：为啥不用 rect2.width = rect1.width，rect3.width = rect2.width + rect1.width 呢?不是更简单吗？

存在即合理，这样的好处是不必用硬编码把逻辑写死，我们可以把常用的转换处理抽象出来，比如封装成一个单纯的dll程序集，以后需要用到的地方，直接引用就可以了，能有效的重用代码。

转自 http://www.cnblogs.com/yjmyzz/archive/2009/12/07/silverlight-binding.html

SL前台调用后台变量

先回忆一下aspx中的处理:

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