WPF 绑定

绑定就是Binding，是控件和数据之间交互的类。

source = {binding}

和

source = {binding RelativeSource={RelativeSource self},Path=DataContext}

效果相同。

例如：直接绑定数据源

前台xaml界面

    <Grid>
        <StackPanel Orientation="Vertical">
            <TextBlock Text="{Binding Number}" Width="50" Height="30" Background="WhiteSmoke" Foreground="Black"/>
            <TextBlock Text="{Binding Name}" Width="50" Height="30" Background="WhiteSmoke" Foreground="Black"/>
            <TextBlock Text="{Binding Class}" Width="50" Height="30" Background="WhiteSmoke" Foreground="Black"/>
        </StackPanel>
 </Grid>

    public partial class MainWindow : Window
    {
        public class StudentInfo
        {
            public int Number { get; set; }
            public string Name { get; set; }
            public string Class { get; set; }
        }
        public MainWindow()
        {
            InitializeComponent();
            List<StudentInfo> list = new List<StudentInfo>();
            for (int i = 0; i < 10; i++)
            {
                StudentInfo entity1 = new StudentInfo();
                entity1.Number = i;
                entity1.Name = "其他" + i;
                entity1.Class = "其他" + i + "其他";
                list.Add(entity1);
            }
            this.DataContext = list;
        }
    }

这里最重要的是this.DataContext = list; 不同的时候DataContext 是不一样的

其中RelativeSource有4种模式：

1.RelativeSource Mode=Self，绑定自身的值。

2.RelativeSource Mode=PreviousData，么看懂，反正就是最后一行数据少了（***），图如下

3.TemplatedParent模式，绑定一个模板。

4.FindAncestor模式，绑定特定的类型。

绑定有三种，Binding，PriorityBinding，MultiBinding。

第一种，Binding，单个值绑定

2个控件一旦进行绑定，那么2个控件是相互的，你变化，我也跟着变化。

1.当绑定写在第一个控件上

 

<StackPanel>
            <Slider x:Name="s" Value="{Binding ElementName=t, Path=Text}"></Slider>
            <TextBox x:Name="t" Text="0"></TextBox>
 
            <!--<Slider x:Name="s" Value="0"></Slider>
            <TextBox x:Name="t" Text="{Binding ElementName=s, Path=Value,UpdateSourceTrigger=PropertyChanged}"></TextBox>-->
        </StackPanel>

2.当绑定写在第二个控件上
 <StackPanel>
            <!--<Slider x:Name="s" Value="{Binding ElementName=t, Path=Text}"></Slider>
            <TextBox x:Name="t" Text="0"></TextBox>-->
 
            <Slider x:Name="s" Value="0"></Slider>
            <TextBox x:Name="t" Text="{Binding ElementName=s, Path=Value,UpdateSourceTrigger=PropertyChanged}"></TextBox>
        </StackPanel>

<Window x:Class="Dispatcher.MainWindow"
        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:Dispatcher" xmlns:collection="clr-namespace:System.Collections;assembly=mscorlib" xmlns:sys="clr-namespace:System;assembly=mscorlib"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <local:AsyncDataSource x:Key="AsyncDS" SlowestDP="最慢" SlowerDP="慢" FastDP="快"  />
    </Window.Resources>
    <Grid>
        <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center" DataContext="{Binding Source={StaticResource AsyncDS}}">
            <TextBlock FontSize="18" FontWeight="Bold" Margin="10" HorizontalAlignment="Center">Priority Binding</TextBlock>
            <TextBlock Background="Honeydew" Width="100" HorizontalAlignment="Center">
                <TextBlock.Text>
                    <PriorityBinding FallbackValue="defaultvalue">
                        <Binding Path="SlowestDP" IsAsync="True"/>
                        <Binding Path="SlowerDP" IsAsync="True"/>
                        <Binding Path="FastDP" />
                    </PriorityBinding>
                </TextBlock.Text>
            </TextBlock>
        </StackPanel>
    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
 
namespace Dispatcher
{
    public class AsyncDataSource
    {
        private string _fastDP;
        private string _slowerDP;
        private string _slowestDP;
 
        public AsyncDataSource()
        {
        }
 
        public string FastDP
        {
            get { return _fastDP; }
            set { _fastDP = value; }
        }
 
        public string SlowerDP
        {
            get
            {
                Thread.Sleep(3000); //模拟耗时
                return _slowerDP;
            }
            set { _slowerDP = value; }
        }
 
        public string SlowestDP
        {
            get
            {
                Thread.Sleep(5000); //模拟耗时
                return _slowestDP;
            }
            set { _slowestDP = value; }
        }
    }
}

第三种，MultiBinding

值转换分为单值转换IValueConverter和多值转换IMultiValueConverter。

使用值转化类可以简单轻松的解决前台界面显示数据的变化，解决同一种数据多种表示的难题。

一、单值转换IValueConverter

1.首先建立一个转换类，引用using System.Windows.Data;，然后继承IValueConverter，点击实现接口

    class YesNoToConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            //value就是前台传递过来的值
            switch (value.ToString().ToLower())
            {
                case "y":
                case "ye":
                case "yes":
                    return true;
                case "n":
                case "no":
                case "non":
                    return false;
            }
            return false;
        }
 
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (value is bool)
            {
                if ((bool)value == true)
                    return "yes";
                else
                    return "no";
            }
            return "no";
        }
    }

<Window x:Class="WpfApp2.MainWindow"
        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:WpfApp2"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <local:YesNoToConverter x:Key="yn"/>
    </Window.Resources>
    <StackPanel Margin="10">
        <TextBox Name="txtValue" />
        <WrapPanel Margin="0,10">
            <TextBlock Text="Current value is: " />
            <TextBlock Name="YN" Text="{Binding ElementName=txtValue, Path=Text, Converter={StaticResource yn}}"></TextBlock>
        </WrapPanel>
        <CheckBox IsChecked="{Binding ElementName=txtValue, Path=Text, Converter={StaticResource yn}}" Content="{Binding ElementName=YN,Path=Text}" />
    </StackPanel>
</Window>

二、多值转换IMultiValueConverter 

1.首先建立一个转换类，引用using System.Windows.Data;

   class YesNoToConverter2 : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            //这里的values就是多个值，与前台绑定的数据有关，有几个值，就判断几个值
            if (values == null || values.Length < 2)
                return DependencyProperty.UnsetValue;
            double verValue = (double)values[0];
            double horValue = (double)values[1];
            if (verValue > horValue)
                return new SolidColorBrush(Colors.Green);
            else if (verValue < horValue)
                return new SolidColorBrush(Colors.Red);
            return new SolidColorBrush(Colors.Yellow);
        }
 
        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            return null;
        }
    }

<Window x:Class="WpfApp2.MainWindow"
        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:WpfApp2"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <local:YesNoToConverter2 x:Key="cvtColor"/>
    </Window.Resources>
    <Grid>
        <Label x:Name="label" Content="纵向值：" HorizontalAlignment="Left" Margin="10,40,0,0" VerticalAlignment="Top"/>
        <Label x:Name="label1" Content="横向值：" HorizontalAlignment="Left" Margin="10,80,0,0" VerticalAlignment="Top"/>
        <Slider x:Name="sliderVer" HorizontalAlignment="Left" Margin="75,43,0,0" VerticalAlignment="Top" Width="192"/>
        <Slider x:Name="sliderHor" HorizontalAlignment="Left" Margin="75,81,0,0" VerticalAlignment="Top" Width="192"/>
        <Ellipse   HorizontalAlignment="Left" Height="100" Margin="75,120,0,0" Stroke="Black" VerticalAlignment="Top" Width="100">
            <Ellipse.Fill>
                <MultiBinding Converter="{StaticResource cvtColor}">
                    <Binding Path="Value" ElementName="sliderVer"/>
                    <Binding Path="Value" ElementName="sliderHor"/>
                </MultiBinding>
            </Ellipse.Fill>
        </Ellipse>
    </Grid>
</Window>

拓展：

多值绑定，根据Select下拉框的值来改变Name中背景颜色。

其中，Name和Select都要有属性通知，多值绑定

Select下拉框需要进行事件绑定数据

 <TextBox Style="{StaticResource dgTextBox}"   
                                     Text="{Binding Name,UpdateSourceTrigger=PropertyChanged}">
                                <TextBox.Background>
                                    <MultiBinding  Converter="{StaticResource relayIPColorConverter}">
                                        <Binding Path="Name" />
                                        <Binding Path="Select"  />
                                    </MultiBinding>
                                </TextBox.Background>
                            </TextBox>  

 private void ComboBox_SelectionChanged_2(object sender, SelectionChangedEventArgs e)
        {
            var current = ((sender as ComboBox).DataContext) as StudentInfo;
            switch (((ContentControl)e.AddedItems[0]).Content)
            {
                case "a": current.Type = 1; break;
                case "b": current.Type = 2; break;
                case "c": current.Type = 3; break;
            }
        }

来源:https://blog.csdn.net/u012563853/article/details/124874725