為建立中文知識庫加塊磚　　　　　　　　——中科大胡不歸

0. 前言

在實現(xiàn)類似設置頁面脱茉，常需要實現(xiàn)某組設置項依賴某個屬性陈惰。比如父項是 ToggleButton，打開開關纤掸，可以設定子項的參數(shù)。關閉開關浑塞，子項被 Disable 而無法編輯借跪。這種情況，簡單的 Binding 就可以實現(xiàn)酌壕。

還有種更復雜的情況掏愁，父項是 ComboBox歇由，有多個選項，其中一個選項對應使能開關果港。這種情況我們需要用到 Converter沦泌。

學習WPF: 第五個月。

1. View代碼

<UserControl x:Class="HelloMvvmLight.View.MainDrawer"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:hc="https://handyorg.github.io/handycontrol"
             xmlns:converter="clr-namespace:HelloMvvmLight.Converter"
             mc:Ignorable="d"
             x:Name="MyDrawer"
             DataContext="{Binding Main, Source={StaticResource Locator}}"
             d:DesignWidth="400">
    <Grid Margin="5" Background="White">
        <Grid.Resources>
            <Style x:Key="TitleText" TargetType="TextBlock">
                <Setter Property="Foreground" Value="Gray" />
                <Setter Property="Padding" Value="5,0,0,0" />
                <Setter Property="VerticalAlignment" Value="Center"></Setter>
                <Setter Property="FontFamily" Value="微軟雅黑,SimSun" />
            </Style>
            
            <converter:LangInfo2BoolConverter x:Key="Lang2Bool"/>
        </Grid.Resources>
        
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
        </Grid.RowDefinitions>
        
        <DockPanel Grid.Row="4" Margin="0,0,0,15">
            <TextBlock DockPanel.Dock="Left" Style="{StaticResource TitleText}" Text="下拉演示" Width="60"></TextBlock>
            <ComboBox x:Name="ComboLang" ItemsSource="{Binding LangList}" SelectedItem="{Binding Path=CurrentLang}" 
                      DisplayMemberPath="Name" />
        </DockPanel>
        
        <DockPanel Grid.Row="5" Margin="0,0,0,15">
            <TextBlock DockPanel.Dock="Left" Style="{StaticResource TitleText}" Text="數(shù)字演示" Width="60"></TextBlock>
            <hc:NumericUpDown IsEnabled="{Binding SelectedValue, ElementName=ComboLang, Converter={StaticResource Lang2Bool}}" 
                              Margin="0,0,0,0" Style="{StaticResource NumericUpDownPlus}"/>
        </DockPanel>
    </Grid>
</UserControl>

注意：需要在resource中聲明我們要用的Converter辛掠。

<Grid.Resources>
            <converter:LangInfo2BoolConverter x:Key="Lang2Bool"/>
</Grid.Resources>

2. Converter代碼

using System;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
using HelloMvvmLight.Model;

namespace HelloMvvmLight.Converter
{
    public class LangInfo2BoolConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (targetType == typeof(Boolean)) {
                if (null != value && value is LangInfo item)
                {
                    switch (item.Value)
                    {
                        case "default":
                        {
                            return false;
                        }

                        default:
                        {
                            return true;
                        }
                    }
                }

                return true;
            }
            throw new InvalidOperationException("Converter can only convert to value of type Boolean.");
        }

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

3. 效果演示

參考文章：

1. Binding to a WPF ToggleButton's IsChecked state
2. How do you bind the TextWrapping property of a TextBox to the IsChecked value of a MenuItem?