XAML表单:如何将命令从ViewModel绑定到XAML

Question

我试图将命令绑定到Xaml中的按钮。我可以绑定在ViewModel中声明的属性，并看到它来改变按钮背景的颜色。使用相同的方式将命令添加到按钮上，当我单击按钮时，按钮不会触发命令。

My ViewModel Command Property

    public Color Color
    {
        get
        {
            return Color.Teal;
        }
    }
    public ICommand OpenFileCommand = new Command((object obj) => { 
        Task.Run(() =>
        {
              var pickFileTask = CrossFilePicker.Current.PickFile();
              var data = pickFileTask.Result;
              //OpenDocument(data.FileName, data.DataArray);
        });
    });

Xaml部分:

<!-- Left Panel --> 
            <StackLayout x:Name="leftStack" Orientation="Vertical" BackgroundColor="Transparent">
                <Button  
                    x:Name="btnOpen"
                    BackgroundColor="{Binding Color}" 
                    Command="{Binding OpenFileCommand}"
                    Image="addfile"
                    HorizontalOptions="CenterAndExpand"
                    VerticalOptions="CenterAndExpand"  
                    WidthRequest="40" 
                    HeightRequest="40">
                </Button>

如果我在代码中绑定命令，它将在视图模型类中执行openfilecommand:

btnOpen.Command = viewModel.OpenFileCommand;

Answer 1

对我来说有效的是将iccommand定义为带有getter的属性:

public ICommand OpenFileCommand { get { return new Command(() => TestMethod()); } }

public void TestMethod() {
      //Do stuff here
}

Answer 2

我通过改变视图模型类来定义命令属性。

public ICommand OpenFileCommand 
    {
        get
        { 
            return new Command((object obj) =>
            {
                Task.Run(() =>
                {
                    var pickFileTask = CrossFilePicker.Current.PickFile();
                    var data = pickFileTask.Result;
                    OpenDocument(data.FileName, data.DataArray);
                });
            });
        }
    }