WPF如何将ItemsControl中UserControl的项传递给ViewModel命令？

问题分析 #

你的代码存在两个核心问题，导致无法正确获取要删除的项：

1. CommandParameter绑定错误：CompoundCardControl按钮中CommandParameter="{Binding Compound}"是错误的。DataTemplate的DataContext已经是单个MethodCompound对象（来自ItemsControl的ItemsSource），无需绑定Compound属性，直接绑定当前上下文即可。
2. RelayCommand未正确接收参数：当前DeleteCompoundCommand直接调用ViewModel里的Compound属性，而非命令传递的参数，导致始终传递初始化时的空对象，而非点击项的实际对象。

修复步骤 #

1. 修正按钮的CommandParameter绑定 #

修改CompoundCardControl中按钮的绑定逻辑：

<Button Grid.Column="3" HorizontalAlignment="Right" Style="{StaticResource menuBarButton}"
        Command="{Binding DataContext.DeleteCompoundCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ItemsControl}}}"
        CommandParameter="{Binding}"> <!-- 直接绑定当前DataContext，即单个MethodCompound -->
    <Image Width="12" Height="12"  Source="/Resources/Icons/Delete.png"/>
</Button>

2. 修正ViewModel中的RelayCommand定义 #

改为支持参数的泛型RelayCommand，并正确接收命令参数：

public class MethodDialogViewModel : ViewModelBase
{
    // 保留原有属性，移除不必要的Compound属性
    public DialogModeEnum DialogMode { get; private set; }
    public string WindowTitle { get { return DialogMode == DialogModeEnum.Add ? "New method" : "Edit method"; } }
    public string ButtonText { get { return DialogMode == DialogModeEnum.Add ? "Add" : "Update"; } }
    public Method Method { get; set; }

    // 改为带参数的泛型命令
    public RelayCommand<MethodCompound> DeleteCompoundCommand { get; }

    public MethodDialogViewModel(Method method, DialogModeEnum dialogMode)
    {
        DialogMode = dialogMode;    
        Method = method;
        // 初始化命令，将参数传递给删除方法
        DeleteCompoundCommand = new RelayCommand<MethodCompound>(DeleteCompound);
    }

    private void DeleteCompound(MethodCompound methodCompound)
    {
        if (methodCompound != null)
        {
            // 执行删除逻辑，从集合中移除项
            Method.Compounds.Remove(methodCompound);
            MessageBox.Show(methodCompound.ID);
        }
        else
        {
            MessageBox.Show("Please select a compound.", "Delete compound", MessageBoxButton.OK, MessageBoxImage.Information);
        }
    }
}

3. 确保ItemsSource为ObservableCollection（UI自动更新必备） #

要让删除后UI自动刷新，Method.Compounds必须是ObservableCollection<MethodCompound>类型，而非普通List：

public class Method
{
    // 替换为ObservableCollection
    public ObservableCollection<MethodCompound> Compounds { get; set; } = new ObservableCollection<MethodCompound>();
}

补充说明 #

• 确认你的RelayCommand实现支持泛型参数（若为自定义实现，需添加RelayCommand<T>版本；若使用Prism等MVVM框架，自带的RelayCommand已支持）。
• ViewModel中无需保留public MethodCompound Compound { get; set; }属性，删除操作完全依赖命令参数传递即可。

内容的提问来源于stack exchange，提问作者Peter