笔记03 wpf 在MVVM模式下怎样在Viewmodel里面获得view的控件对象

 转自http://blog.csdn.net/qing2005/article/details/6601199
http://blog.csdn.net/qing2005/article/details/6601475

MVVM中轻松实现Command绑定（二）传递Command参数

属性栏里去设置的。语句应该是CommandParameter="{Binding ElementName=控件名}"

我们如果需要在Command中传递参数，实现也很简单。DelegateCommand还有一个DelegateCommand<T>版本，可以传递一个T类型的参数。

1.View的Button绑定，其中CommandParameter定义了一个“20”的参数

<Window x:Class="WpfApplication1.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="clr-namespace:WpfApplication1"
        Title="Window1" Height="193" Width="190">
    <Window.DataContext>
        <vm:Window1ViewModel />
    </Window.DataContext>
    <Grid>
        <Button Content="Button" Height="33" HorizontalAlignment="Left" Margin="34,20,0,0" Name="button1" VerticalAlignment="Top" Width="109"
                Command="{Binding ButtonCommand}"
                CommandParameter="20"/>
    </Grid>
</Window>

2.ViewModel定义命令，注意委托参数

namespace WpfApplication1 {
    public class Window1ViewModel {

        public ICommand ButtonCommand {
            get {
                return new DelegateCommand<string>((str) => {
                    MessageBox.Show("Button's parameter:"+str);
                });
            }
        }

    }
}

并且，特殊情况下，我们可以将控件对象作为参数传递给ViewModel，注意{Binding RelativeSource={x:Static RelativeSource.Self}}是绑定自己（Button）的意思。

<Window x:Class="WpfApplication1.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="clr-namespace:WpfApplication1"
        Title="Window1" Height="193" Width="190">
    <Window.DataContext>
        <vm:Window1ViewModel />
    </Window.DataContext>
    <Grid>
        <Button Content="Button" Height="33" HorizontalAlignment="Left" Margin="34,20,0,0" Name="button1" VerticalAlignment="Top" Width="109"
                Command="{Binding ButtonCommand}"
                CommandParameter="20"/>
        <Button Content="Button" Height="33" HorizontalAlignment="Left" Margin="34,85,0,0" Name="button2" VerticalAlignment="Top" Width="109"
                Command="{Binding ButtonCommand2}"
                CommandParameter="{Binding RelativeSource={x:Static RelativeSource.Self}}"/>
    </Grid>
</Window>

再看ViewModel

namespace WpfApplication1 {
    public class Window1ViewModel {

        public ICommand ButtonCommand {
            get {
                return new DelegateCommand<string>((str) => {
                    MessageBox.Show("Button's parameter:"+str);
                });
            }
        }

        public ICommand ButtonCommand2 {
            get {
                return new DelegateCommand<Button>((button) => {
                    button.Content = "Clicked";
                    MessageBox.Show("Button");
                });
            }
        }
    }
}

这样就可以在委托中获取Button对象了。但是MVVM本身比建议ViewModel操作View。