理解Prism中MVVM的Command与CommandParameter

内容摘要

接上一讲（http://www.cnblogs.com/chenxizhang/archive/2012/04/13/2446415.html），这一讲中我使用Prism做了演示和比较。Prism不仅仅是一个MVVM框架，它还包含其他的模块。在MVVM这个层面，Prism有些特殊性（Command绑定有特殊语法），这也是我这一讲的主要内容。

Prism的下载链接

http://compositewpf.codeplex.com/

视频地址

http://www.tudou.com/programs/view/72Ag1kQt1RA/

示例代码

<Window x:Class="WPFPrismMvvm.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow"
        Height="350"
        xmlns:local="clr-namespace:WPFPrismMvvm"
        xmlns:cmd="clr-namespace:Microsoft.Practices.Prism.Commands;assembly=Microsoft.Practices.Prism"
        Width="525">
    <Window.DataContext>
        <local:MainWindowViewModel UserName="chenxizhang"></local:MainWindowViewModel>
    </Window.DataContext>
    <Grid>

        <StackPanel>

            <TextBox Text="{Binding UserName,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"></TextBox>

            <Button Content="Show"
                    cmd:Click.Command="{Binding ShowCommand}"
                    cmd:Click.CommandParameter="{Binding UserName}"></Button>
        </StackPanel>
    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Microsoft.Practices.Prism.ViewModel;
using Microsoft.Practices.Prism.Commands;
using System.Windows.Input;
using System.Windows;

namespace WPFPrismMvvm
{
    public class MainWindowViewModel:NotificationObject
    {

        private string _UserName;
        public string UserName
        {
            get { return _UserName; }
            set
            {
                if (_UserName != value)
                {
                    _UserName = value;
                    RaisePropertyChanged("UserName");
                }
            }
        }



        public ICommand ShowCommand
        {
            get
            {
                return new DelegateCommand<string>(
                    (user) =>
                    {
                        MessageBox.Show(user);
                    }, (user) => {
                        return !string.IsNullOrEmpty(user);
                    });

            }
        }
    }
}