稳扎稳打Silverlight(15) - 2.0数据之一次绑定, 单向绑定, 双向绑定, INotifyPropertyChanged, 数据转换

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稳扎稳打Silverlight(15) - 2.0数据之一次绑定, 单向绑定, 双向绑定, INotifyPropertyChanged, 数据转换, 数据验证

作者：webabcd


介绍
Silverlight 2.0 数据绑定：
    Binding - 将绑定目标对象的属性与数据源联接起来
        Source - 绑定的数据源
        Mode - 绑定的数据流的方向 [System.Windows.Data.BindingMode枚举]
            BindingMode.OneTime - 一次绑定。创建绑定时一次性地更新绑定目标对象的属性
            BindingMode.OneWay - 单向绑定（默认值）。数据源的改变会自动通知到绑定目标对象的属性
            BindingMode.TwoWay - 双向绑定。数据源或绑定目标对象的属性的值发生改变时会互相通知。显然，做数据验证的话一定要是双向绑定
        Path - 需要绑定的属性名称
        NotifyOnValidationError - 产生验证错误时是否触发 BindingValidationError 事件。默认值为 false
        ValidatesOnExceptions - 产生验证错误时绑定引擎是否要报告错误。默认值为 false
    INotifyPropertyChanged - 向客户端发出某一属性值已更改的通知
    IValueConverter - 值转换接口，将一个类型的值转换为另一个类型的值。它提供了一种将自定义逻辑应用于绑定的方式
        Convert - 正向转换器。将值从数据源传给绑定目标时，数据绑定引擎会调用此方法
        ConvertBack - 反向转换器。将值从绑定目标传给数据源时，数据绑定引擎会调用此方法
    BindingValidationError - 出现验证错误或解决上次验证错误则触发此事件


在线DEMO
http://webabcd.blog.51cto.com/1787395/342779 


示例
1、NotifyProperty.xaml（演示INotifyPropertyChanged）

<UserControl x:Class="Silverlight20.Data.NotifyProperty"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
        <StackPanel HorizontalAlignment="Left">

                <!--
                Binding - 将绑定目标对象的属性与数据源联接起来（本例为将 Ellipse的Fill属性 与 MyColor的Brush属性 相联）
                Mode - Binding 的扩展属性之一，默认为 OneWay（单向绑定），即数据源的改变会自动通知到绑定目标对象的属性
                -->
                <Ellipse x:Name="ellipse" Width="100" Height="50" Fill="{Binding Brush, Mode=OneWay}" MouseLeftButtonDown="ellipse_MouseLeftButtonDown" />

        </StackPanel>
</UserControl>

 

NotifyProperty.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using System.ComponentModel;

namespace Silverlight20.Data
{
        public partial class NotifyProperty : UserControl
        {
                MyColor _myColor;

                public NotifyProperty()
                {
                        InitializeComponent();

                        this.Loaded += new RoutedEventHandler(NotifyProperty_Loaded);
                }

                void NotifyProperty_Loaded(object sender, RoutedEventArgs e)
                {
                        _myColor = new MyColor { Brush = new SolidColorBrush(Colors.Red) };

                        // DataContext - FrameworkElement 做数据绑定时的数据上下文
                        // 将 MyColor 对象绑定到 Ellipse
                        ellipse.DataContext = _myColor;
                }

                private void ellipse_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
                {
                        // 鼠标按下后修改 MyColor 对象的属性
                        // 如果MyColor实现了INotifyPropertyChanged接口，并且绑定目标的BindingMode为OneWay或者TwoWay的话则会自动通知到绑定目标
                        if (_myColor.Brush.Color == Colors.Red)
                                _myColor.Brush = new SolidColorBrush(Colors.Green);
                        else
                                _myColor.Brush = new SolidColorBrush(Colors.Red);
                }
        }

        /*
         * INotifyPropertyChanged - 向客户端发出某一属性值已更改的通知
         * 使用 OneWay 或者 TwoWay 的话必须要实现 INotifyPropertyChanged 接口
        */
        public class MyColor : INotifyPropertyChanged
        {
                private SolidColorBrush _brush;
                public SolidColorBrush Brush
                {
                        get { return _brush; }
                        set
                        {
                                _brush = value;
                                if (PropertyChanged != null)
                                {
                                        // 触发 PropertyChanged 事件，事件参数为属性名称
                                        PropertyChanged(this, new PropertyChangedEventArgs("Brush"));
                                }
                        }
                }

                // 声明一个 PropertyChanged 事件
                public event PropertyChangedEventHandler PropertyChanged;
        }
}

 

2、Conversion.xaml（演示数据转换）

<!--引用转换器所在的命名空间-->
<UserControl x:Class="Silverlight20.Data.Conversion"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:custom="clr-namespace:Silverlight20.Data">
        
        <UserControl.Resources>
        
                <!--在资源中声明转换器-->
                <custom:ColorEnumToBrush x:Key="converter" />
                
        </UserControl.Resources>
        
        <StackPanel HorizontalAlignment="Left">

                <!--
                Converter - 用于指定转换器
                ConverterParameter - 转换器所使用的参数
                ConverterCulture - 转换器所使用的区域信息
                -->
                <Ellipse x:Name="ellipse" Width="100" Height="50" MouseLeftButtonDown="ellipse_MouseLeftButtonDown"    
                        Fill="{Binding ColorEnum, Converter={StaticResource converter}, ConverterParameter=10}"    
                />

        </StackPanel>
</UserControl>

 

Conversion.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using System.ComponentModel;
using System.Windows.Data;

namespace Silverlight20.Data
{
        public partial class Conversion : UserControl
        {
                MyColorEnum _myColorEnum;

                public Conversion()
                {
                        InitializeComponent();

                        this.Loaded += new RoutedEventHandler(Conversion_Loaded);
                }

                void Conversion_Loaded(object sender, RoutedEventArgs e)
                {
                        _myColorEnum = new MyColorEnum() { ColorEnum = ColorEnum.Red };

                        // DataContext - FrameworkElement 做数据绑定时的数据上下文
                        // 将 MyColorEnum 对象绑定到 Ellipse
                        ellipse.DataContext = _myColorEnum;
                }

                private void ellipse_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
                {
                        // 鼠标按下后修改 MyColorEnum 对象的属性
                        if (_myColorEnum.ColorEnum == ColorEnum.Red)
                                _myColorEnum.ColorEnum = ColorEnum.Green;
                        else
                                _myColorEnum.ColorEnum = ColorEnum.Red;
                }
        }

        /*
         * IValueConverter - 值转换接口，将一个类型的值转换为另一个类型的值。它提供了一种将自定义逻辑应用于绑定的方式
         *         Convert - 正向转换器。将值从数据源传给绑定目标时，数据绑定引擎会调用此方法
         *         ConvertBack - 反向转换器。将值从绑定目标传给数据源时，数据绑定引擎会调用此方法
        */
        public class ColorEnumToBrush : IValueConverter
        {
                /// <summary>
                /// 正向转换器。将值从数据源传给绑定目标时，数据绑定引擎会调用此方法
                /// </summary>
                /// <param name="value">转换之前的值</param>
                /// <param name="targetType">转换之后的类型</param>
                /// <param name="parameter">转换器所使用的参数</param>
                /// <param name="culture">转换器所使用的区域信息</param>
                /// <returns>转换后的值</returns>
                public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
                {
                        // 将 ColorEnum 类型的值转换为 SolidColorBrush 类型的值

                        // parameter == 10

                        ColorEnum color = (ColorEnum)value;

                        SolidColorBrush brush = new SolidColorBrush(Colors.Red);

                        if (color == ColorEnum.Green)
                                brush = new SolidColorBrush(Colors.Green);

                        return brush;
                }

                /// <summary>
                /// 反向转换器。将值从绑定目标传给数据源时，数据绑定引擎会调用此方法
                /// </summary>
                /// <param name="value">转换之前的值</param>
                /// <param name="targetType">转换之后的类型</param>
                /// <param name="parameter">转换器所使用的参数</param>
                /// <param name="culture">转换器所使用的区域信息</param>
                /// <returns>转换后的值</returns>
                public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
                {
                        return null;
                }
        }

        /*
         * INotifyPropertyChanged - 向客户端发出某一属性值已更改的通知
         * 使用 OneWay 或者 TwoWay 的话必须要实现 INotifyPropertyChanged 接口
        */
        public class MyColorEnum : INotifyPropertyChanged
        {
                private ColorEnum _colorEnum;
                public ColorEnum ColorEnum
                {
                        get { return _colorEnum; }
                        set
                        {
                                _colorEnum = value;
                                if (PropertyChanged != null)
                                {
                                        // 触发 PropertyChanged 事件，事件参数为属性名称
                                        PropertyChanged(this, new PropertyChangedEventArgs("ColorEnum"));
                                }
                        }
                }

                // 声明一个 PropertyChanged 事件
                public event PropertyChangedEventHandler PropertyChanged;
        }

        /// <summary>
        /// 自定义的 ColorEnum 枚举
        /// </summary>
        public enum ColorEnum
        {
                Red,
                Green
        }
}

 

 

3、Validation.xaml（演示数据验证）

<!--引用验证类所在的命名空间-->
<UserControl x:Class="Silverlight20.Data.Validation"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:custom="clr-namespace:Silverlight20.Data">
        
        <!--
        BindingValidationError - 出现验证错误或解决上次验证错误则触发此事件
        -->
        <StackPanel HorizontalAlignment="Left" BindingValidationError="StackPanel_BindingValidationError" >
                
                <StackPanel.Resources>
                
                        <!--在资源中声明验证类-->
                        <custom:MyValidation x:Name="myValidation"/>
                        
                </StackPanel.Resources>
                
                <TextBox x:Name="textBox" Width="200" Margin="5">
                        <TextBox.Text>
                        
                                <!--
                                Binding - 将绑定目标对象的属性与数据源联接起来
                                        Source - 绑定的数据源
                                        Mode - 绑定的数据流的方向 [System.Windows.Data.BindingMode枚举]
                                                BindingMode.OneTime - 一次绑定。创建绑定时一次性地更新绑定目标对象的属性
                                                BindingMode.OneWay - 单向绑定（默认值）。数据源的改变会自动通知到绑定目标对象的属性
                                                BindingMode.TwoWay - 双向绑定。数据源或绑定目标对象的属性的值发生改变时会互相通知。显然，做数据验证的话一定要是双向绑定
                                        Path - 需要绑定的属性名称
                                        NotifyOnValidationError - 产生验证错误时是否触发 BindingValidationError 事件。默认值为 false
                                        ValidatesOnExceptions - 产生验证错误时绑定引擎是否要报告错误。默认值为 false
                                -->
                                <Binding    
                                        Source="{StaticResource myValidation}"    
                                        Mode="TwoWay"    
                                        Path="Count"
                                        NotifyOnValidationError="True"    
                                        ValidatesOnExceptions="True"
                                />
                                        
                        </TextBox.Text>
                </TextBox>
                
                <TextBox x:Name="textBox2" Width="200"    Margin="5" />
                        
        </StackPanel>
        
</UserControl>

 

Validation.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using System.Text.RegularExpressions;

namespace Silverlight20.Data
{
        public partial class Validation : UserControl
        {
                public Validation()
                {
                        InitializeComponent();
                }

                private void StackPanel_BindingValidationError(object sender, ValidationErrorEventArgs e)
                {
                        // ValidationErrorEventArgs - 用于提供 BindingValidationError 事件的一些信息
                        //         ValidationErrorEventArgs.Action - 验证状态
                        //         ValidationErrorEventArgs.Error - 触发 BindingValidationError 事件的错误信息
                        //         ValidationErrorEventArgs.Handled - 标记该路由事件是否已被处理
                        // ValidationErrorEventAction.Added - 因为出现验证错误而触发此事件
                        // ValidationErrorEventAction.Removed - 因为解决上次验证错误而触发此事件

                        if (e.Action == ValidationErrorEventAction.Added)
                        {
                                textBox.Background = new SolidColorBrush(Colors.Red);
                                textBox.Text = e.Error.Exception.Message;
                        }
                        else if (e.Action == ValidationErrorEventAction.Removed)
                        {
                                textBox.Background = new SolidColorBrush(Colors.White);
                        }
                }
        }

        /// <summary>
        /// 验证类。验证是否为正整数
        /// </summary>
        public class MyValidation
        {
                private string _count;
                public string Count
                {
                        get { return _count; }
                        set
                        {
                                if (!Regex.IsMatch(value, @"^\d+$"))
                                {
                                        // 绑定引擎可以报告由属性的 setter 抛出的异常，也可以报告由转换器（IValueConverter）抛出的异常
                                        throw new Exception("必须是正整数");
                                }

                                _count = value;
                        }
                }
        }
}

 

 

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