WPF ComboBox SelectionChanged事件导致命令不触发

Question

我有以下XAML，ComboBox其中具有代码隐藏SelectionChanged事件处理程序和ViewModel的另一个Command属性。我将SelectedIndex属性设置为0。现在，当我运行项目时，将调用代码隐藏处理程序，但Command不会执行。我想要的是Command应该SelectedIndex=0在视图第一次加载时执行。

<ComboBox Name="listComboBox" SelectionChanged="listComboBox_SelectionChanged" SelectedIndex="0" SelectedValuePath="Content" Margin="5,0" Height="35" Width="150" VerticalAlignment="Center" HorizontalAlignment="Left">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="SelectionChanged">
            <i:InvokeCommandAction Command="{Binding ListTypeComboSelectionChangedCmd}" CommandParameter="{Binding ElementName=listComboBox, Path=SelectedValue}"/>
        </i:EventTrigger>
     </i:Interaction.Triggers>
     <ComboBoxItem Content="ItemOne" />
     <ComboBoxItem Content="ItemTwo" />
     <ComboBoxItem Content="ItemThree" />
</ComboBox>

更新资料

代码隐藏事件处理程序：

<ComboBox Name="listComboBox" SelectionChanged="listComboBox_SelectionChanged" SelectedIndex="0" SelectedValuePath="Content" Margin="5,0" Height="35" Width="150" VerticalAlignment="Center" HorizontalAlignment="Left">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="SelectionChanged">
            <i:InvokeCommandAction Command="{Binding ListTypeComboSelectionChangedCmd}" CommandParameter="{Binding ElementName=listComboBox, Path=SelectedValue}"/>
        </i:EventTrigger>
     </i:Interaction.Triggers>
     <ComboBoxItem Content="ItemOne" />
     <ComboBoxItem Content="ItemTwo" />
     <ComboBoxItem Content="ItemThree" />
</ComboBox>

ICommand对象：

private void listComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e) { }

ICommand处理程序：

public ICommand ListTypeComboSelectionChangedCmd 
{ 
    get { return new RelayCommand<string>(ListTypeComboSelectionChangedCmdExec); }
    private set;
}

Answer 1

绑定SelectedValue到Property视图模型上的a 。

在Property set{...}块中做你的逻辑或调用

ListTypeComboSelectionChangedCmdExec(value)

请参阅使用 MVVM 绑定 ComboBox SelectedItem