wpf之DataTrigger 数据触发器

     wpf中，根据数据的值的不同，UI的界面随之改变(显示控件、隐藏控件以及改变控件的其它属性)，

这时我们可以用DataTrigger数据触发器。

    下面两个案例实现同样的功能，当条件(数据的值)不同时，显示不同的按钮。

创建 Core类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;

namespace DataTriggerDemo2
{
    public class Core : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged(string propertyName)
        {
            if (this.PropertyChanged != null)
            {
                this.PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        private string condition;

        public string Condition
        {
            get { return condition; }
            set
            {
                condition = value;
                OnPropertyChanged("Condition");
            }
        }
    }
}

XAML:

<Window x:Class="DataTriggerDemo2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:DataTriggerDemo2"
        Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">
    <Window.Resources>
        <local:Core x:Key="core" />

        <Style TargetType="{x:Type Button}">
            <Setter Property="Margin" Value="5" />
            <Setter Property="Padding" Value="0,8.5" />
            <Setter Property="FontSize" Value="16" />
        </Style>
    </Window.Resources>
    <Grid>
        <ContentControl>
            <ContentControl.ContentTemplate>
                <DataTemplate>
                    <DockPanel LastChildFill="True" DataContext="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=Window, AncestorLevel=1}, Path=DataContext}">
                        <TextBlock DockPanel.Dock="Top" Text="按钮列表" HorizontalAlignment="Center" FontSize="18"/>
                        <Border DockPanel.Dock="Right" Width="160">
                            <StackPanel Orientation="Vertical">
                                <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center" Foreground="Red" FontSize="16" Text="{Binding Source={StaticResource ResourceKey=core},Path=Condition}"/>
                                <Button x:Name="btn1" Content="编辑按钮1" Visibility="Collapsed"/>
                                <Button x:Name="btn2" Content="编辑按钮2" Visibility="Collapsed"/>
                                <Button x:Name="btn3" Content="编辑按钮3" Visibility="Collapsed"/>
                                <Button x:Name="btn4" Content="编辑按钮4" Visibility="Collapsed"/>
                            </StackPanel>
                        </Border>
                    </DockPanel>
                    <DataTemplate.Triggers>
                        <DataTrigger Binding="{Binding Source={StaticResource ResourceKey=core},Path=Condition}" Value="条件1">
                            <Setter TargetName="btn1" Property="Visibility" Value="Visible"/>
                        </DataTrigger>
                        <DataTrigger Binding="{Binding Source={StaticResource ResourceKey=core},Path=Condition}" Value="条件2">
                            <Setter TargetName="btn1" Property="Visibility" Value="Visible"/>
                            <Setter TargetName="btn2" Property="Visibility" Value="Visible"/>
                        </DataTrigger>
                        <DataTrigger Binding="{Binding Source={StaticResource ResourceKey=core},Path=Condition}" Value="条件3">
                            <Setter TargetName="btn1" Property="Visibility" Value="Visible"/>
                            <Setter TargetName="btn2" Property="Visibility" Value="Visible"/>
                            <Setter TargetName="btn3" Property="Visibility" Value="Visible"/>
                        </DataTrigger>
                        <DataTrigger Binding="{Binding Source={StaticResource ResourceKey=core},Path=Condition}" Value="条件4">
                            <Setter TargetName="btn1" Property="Visibility" Value="Visible"/>
                            <Setter TargetName="btn2" Property="Visibility" Value="Visible"/>
                            <Setter TargetName="btn3" Property="Visibility" Value="Visible"/>
                            <Setter TargetName="btn4" Property="Visibility" Value="Visible"/>
                        </DataTrigger>
                    </DataTemplate.Triggers>
                </DataTemplate>
            </ContentControl.ContentTemplate>
        </ContentControl>
    </Grid>
</Window>

C#:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace DataTriggerDemo2
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        private Core core;
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            core = this.FindResource("core") as Core;
            core.Condition = "条件3";
        }
    }
}

Loaded方法里赋值：  core.Condition = "条件3"，

则数据触发器触发相应的DataTrigger：

运行结果只显示三个按钮：

wpf的灵活之处在与，同样的效果可以用很多种方法实现。

下面介绍另一种实现方法：

首先创建wpf应用程序，引用下面两个dll：

Xaml头部引用名称空间：

        xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
        xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"

完整Xaml:

<Window x:Class="DataTriggerDemo.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:ei="http://schemas.microsoft.com/expression/2010/interactions"
        xmlns:local="clr-namespace:DataTriggerDemo"
        Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded" DataContext="{DynamicResource ResourceKey=core}">
    <Window.Resources>
        <local:Core x:Key="core" />
    </Window.Resources>
    <Grid>
        <DockPanel LastChildFill="True" DataContext="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=Window, AncestorLevel=1}, Path=DataContext}">
            <TextBlock DockPanel.Dock="Top" Text="按钮列表" HorizontalAlignment="Center" FontSize="18"/>
            <Border DockPanel.Dock="Right" Width="160">
                <StackPanel Orientation="Vertical">
                    <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center" FontSize="18" Text="{Binding Path=Condition}"/>
                    <Button x:Name="btn1" Content="编辑按钮1" Visibility="Collapsed"/>
                    <Button x:Name="btn2" Content="编辑按钮2" Visibility="Collapsed"/>
                    <Button x:Name="btn3" Content="编辑按钮3" Visibility="Collapsed"/>
                    <Button x:Name="btn4" Content="编辑按钮4" Visibility="Collapsed"/>
                </StackPanel>
            </Border>
        </DockPanel>
        <i:Interaction.Triggers>
            <ei:DataTrigger Binding="{Binding Path=Condition}" Value="条件1">
                <ei:ChangePropertyAction TargetObject="{Binding ElementName=btn1}" TargetName="Button" PropertyName="Visibility" Value="Visible"/>
                <ei:ChangePropertyAction TargetObject="{Binding ElementName=btn2}" TargetName="Button" PropertyName="Visibility" Value="Visible"/>
                <ei:ChangePropertyAction TargetObject="{Binding ElementName=btn3}" TargetName="Button" PropertyName="Visibility" Value="Visible"/>
                <ei:ChangePropertyAction TargetObject="{Binding ElementName=btn4}" TargetName="Button" PropertyName="Visibility" Value="Visible"/>
            </ei:DataTrigger>
            <ei:DataTrigger Binding="{Binding Path=Condition}" Value="条件2">
                <ei:ChangePropertyAction TargetObject="{Binding ElementName=btn2}" TargetName="Button" PropertyName="Visibility" Value="Visible"/>
                <ei:ChangePropertyAction TargetObject="{Binding ElementName=btn3}" TargetName="Button" PropertyName="Visibility" Value="Visible"/>
                <ei:ChangePropertyAction TargetObject="{Binding ElementName=btn4}" TargetName="Button" PropertyName="Visibility" Value="Visible"/>
            </ei:DataTrigger>
            <ei:DataTrigger Binding="{Binding Path=Condition}" Value="条件3">
                <ei:ChangePropertyAction TargetObject="{Binding ElementName=btn3}" TargetName="Button" PropertyName="Visibility" Value="Visible"/>
                <ei:ChangePropertyAction TargetObject="{Binding ElementName=btn4}" TargetName="Button" PropertyName="Visibility" Value="Visible"/>
            </ei:DataTrigger>
            <ei:DataTrigger Binding="{Binding Path=Condition}" Value="条件4">
                <ei:ChangePropertyAction TargetObject="{Binding ElementName=btn4}" TargetName="Button" PropertyName="Visibility" Value="Visible"/>
            </ei:DataTrigger>
        </i:Interaction.Triggers>
    </Grid>
</Window>

C#:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace DataTriggerDemo
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        private Core core;
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            core = this.FindResource("core") as Core;
            core.Condition = "条件3";
        }
    }
}

窗体的 loaded事件加载数据时设置 core.Condition = "条件3"，

运行结果如下图：

与XAML里的数据触发器执行的预期效果是一样的：