筆記03 wpf 在MVVM模式下怎樣在Viewmodel里面獲得view的控件對象

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

MVVM中輕松實現Command綁定（二）傳遞Command參數

屬性欄里去設置的。語句應該是CommandParameter="{Binding ElementName=控件名}"

我們如果需要在Command中傳遞參數，實現也很簡單。DelegateCommand還有一個DelegateCommand<T>版本，可以傳遞一個T類型的參數。

1.View的Button綁定，其中CommandParameter定義了一個“20”的參數

<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定義命令，注意委托參數

namespace WpfApplication1 {
    public class Window1ViewModel {

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

    }
}

並且，特殊情況下，我們可以將控件對象作為參數傳遞給ViewModel，注意{Binding RelativeSource={x:Static RelativeSource.Self}}是綁定自己（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");
                });
            }
        }
    }
}

這樣就可以在委托中獲取Button對象了。但是MVVM本身比建議ViewModel操作View。