MVVM中轻松实现Command绑定（二）传递Command参数

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“Baby”的参数

<Window x:Class="MVVMCommand.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:MVVMCommand"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<local:MainWindowViewModel/>
</Window.DataContext>
<Grid>
<Button Content="Button" Command="{Binding ButtonCommand}"
CommandParameter="Baby"/>
</Grid>
</Window>
2.ViewModel定义命令，注意委托参数

namespace MVVMCommand{
public class MainWindowViewModel{

public ICommand ButtonCommand{
get{
return new DelegateCommand<string>(new Action<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="MVVMCommand.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:MVVMCommand"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<local:MainWindowViewModel/>
</Window.DataContext>
<Grid>
<Button Content="Button" Command="{Binding ButtonCommand}"
CommandParameter="{Binding RelativeSource={x:Static RelativeSource.Self}}"/>
</Grid>
</Window>
再看ViewModel

namespace MVVMCommand{
public class MainWindowViewModel{

public ICommand ButtonCommand{
get{
return new DelegateCommand<Button>(new Action<Button>((btn) =>{
btn.Content = "Clicked";
}));
}
}
}
}