WPF中的转换器

单值转换器

1.创建项目后下载两个NuGet程序包

2.先定义一个转换器实现IValueConverter接口

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Data;

namespace WPF练习14单值转换器.Converter
{
    public class BoolToVisibilityConverter : IValueConverter
    {
        // Convert负责把源数据类型转换成目标数据类型
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            bool oldType = (bool)value; // 源数据类型
            Visibility newType = oldType ? Visibility.Visible : Visibility.Collapsed; // 目标类型
            return newType;
        }
        // ConvertBack负责目标数据类型转换成源数据类型
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}

3.在ViewModel文件夹中创建MainWindowViewModel

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WPF练习14单值转换器.ViewModel
{
    public class MainWindowViewModel : ObservableObject
    {
		private bool isShow=true;

		public bool IsShow
		{
			get => isShow;
			set => SetProperty(ref isShow, value);
		}
        public RelayCommand UpdateIsShowCommand
        {
            get
            {
                return new RelayCommand(() =>
                {
                    IsShow = !IsShow;
                });
            }
        }

    }
}

4.把转换器当成一个资源导入到XAML文件中 并且将MainWindowViewModel导入DataContext上下文中

<Window x:Class="WPF练习14单值转换器.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:WPF练习14单值转换器"
        xmlns:c="clr-namespace:WPF练习14单值转换器.Converter"
        xmlns:vm="clr-namespace:WPF练习14单值转换器.ViewModel"
        mc:Ignorable="d"
        Title="MainWindow"
        Height="450"
        Width="800">
    <Window.DataContext>
        <vm:MainWindowViewModel />
    </Window.DataContext>
    <Window.Resources>
        <c:BoolToVisibilityConverter x:Key="boolToVisibilityConverter" />
    </Window.Resources>
    <Grid>
        <WrapPanel Orientation="Vertical">
            <Button Width="100"
                    Height="30"
                    HorizontalAlignment="Left"
                    Content="显示/隐藏"
                    Visibility="{Binding IsShow, Converter={StaticResource boolToVisibilityConverter}}" />

            <Button Width="100"
                    Height="30"
                    HorizontalAlignment="Left"
                    Command="{Binding UpdateIsShowCommand}"
                    Content="修改IsShow" />
        </WrapPanel>
       
    </Grid>
</Window>

多值转换器（结构同上）

ObjToArrConverter如下：

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Data;

namespace WPF练习14单值转换器.Converter
{
    public class ObjToArrConverter : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            return values.ToArray();
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}

MainWindowViewModel如下：

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;

namespace WPF练习14单值转换器.ViewModel
{
    public class MainWindowViewModel : ObservableObject
    {
        public RelayCommand<object[]> Command3
        {
            get
            {
                return new RelayCommand<object[]>((arr) =>
                {

                    MessageBox.Show(arr[0].ToString());
                    MessageBox.Show(arr[1].ToString());
                    MessageBox.Show(arr[2].ToString());
                });
            }
        }

    }
}

MainWindow.XAML如下：

<Window x:Class="WPF练习14单值转换器.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:WPF练习14单值转换器"
        xmlns:c="clr-namespace:WPF练习14单值转换器.Converter"
        xmlns:vm="clr-namespace:WPF练习14单值转换器.ViewModel"
        xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
        mc:Ignorable="d"
        Title="MainWindow"
        Height="450"
        Width="800">
    <Window.DataContext>
        <vm:MainWindowViewModel />
    </Window.DataContext>
    <Window.Resources>
        <c:ObjToArrConverter x:Key="objToArrConverter" />
    </Window.Resources>
    <Grid>
        <WrapPanel Orientation="Vertical">
            <TextBox x:Name="Id" />
            <TextBox x:Name="Name" />
            <TextBox x:Name="Status" />
            <TextBlock Width="150"
                       Height="30"
                       HorizontalAlignment="Left"
                       Text="传递多个参数">
     <i:Interaction.Triggers>
         <i:EventTrigger EventName="MouseLeftButtonUp">
             <i:InvokeCommandAction Command="{Binding Command3}">
                 <i:InvokeCommandAction.CommandParameter>
                     <MultiBinding Converter="{StaticResource objToArrConverter}">
                         <Binding ElementName="Id"
                                    Path="Text" />
                         <Binding ElementName="Name"
                                    Path="Text" />
                         <Binding ElementName="Status"
                                    Path="Text" />
                     </MultiBinding>
                 </i:InvokeCommandAction.CommandParameter>
             </i:InvokeCommandAction>
         </i:EventTrigger>
     </i:Interaction.Triggers>
            </TextBlock>
        </WrapPanel>

    </Grid>
</Window>

按钮传递多个参数和这个类似