梦琪小生 【转】【WPF】WPF MVVM 简单实例

1 新建WPF 应用程序WPFMVVMExample

程序结构如下图所示。

2 Model实现

在Model文件夹下新建业务类StudentModel（类文件StudentModel.cs），类的详细代码如下所示。

using System.ComponentModel;

namespace WPFMVVMExample.Model
{
    public class StudentModel : INotifyPropertyChanged
    {
        /// <summary>
        /// 学号
        /// </summary>
        private int studentId;
        public int StudentId
        {
            get
            {
                return studentId;
            }
            set
            {
                studentId = value;
                NotifyPropertyChanged("StudentId");
            }
        }

        /// <summary>
        /// 姓名
        /// </summary>
        private string studentName;
        public string StudentName
        {
            get
            {
                return studentName;
            }
            set
            {
                studentName = value;
                NotifyPropertyChanged("StudentName");
            }
        }

        /// <summary>
        /// 年龄
        /// </summary>
        private int studentAge;
        public int StudentAge
        {
            get
            {
                return studentAge;
            }
            set
            {
                studentAge = value;
                NotifyPropertyChanged("StudentAge");
            }
        }

        /// <summary>
        /// Email
        /// </summary>
        private string studentEmail;
        public string StudentEmail
        {
            get
            {
                return studentEmail;
            }
            set
            {
                studentEmail = value;
                NotifyPropertyChanged("StudentEmail");
            }
        }

        /// <summary>
        /// 性别
        /// </summary>
        private string studentSex;
        public string StudentSex
        {
            get
            {
                return studentSex;
            }
            set
            {
                studentSex = value;
                NotifyPropertyChanged("StudentSex");
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        public void NotifyPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}

StudentModel类实现了接口INotifyPropertyChanged。当类实现该接口后，便可以向执行绑定的客户端发出某一属性值已更改的通知。

3 ViewModel实现

在ViewModel文件夹下新建类文件StudentViewModel.cs,类文件的详细代码如下所示。

using System;
using System.Windows.Input;
using WPFMVVMExample.Model;

namespace WPFMVVMExample.ViewModel
{
    public class StudentViewModel
    {
        public DelegateCommand ShowCommand { get; set; }
        public StudentModel Student { get; set; }
        public StudentViewModel()
        {
            Student = new StudentModel();
            ShowCommand=new DelegateCommand();
            ShowCommand.ExecuteCommand = new Action<object>(ShowStudentData);
        }
        private void ShowStudentData(object obj)
        {
            Student.StudentId = 1;
            Student.StudentName = "tiana";
            Student.StudentAge = 20;
            Student.StudentEmail = "8644003248@qq.com";
            Student.StudentSex = "大帅哥";
        }

    }

    public class DelegateCommand : ICommand
    {
        public Action<object> ExecuteCommand = null;
        public Func<object, bool> CanExecuteCommand = null;
        public event EventHandler CanExecuteChanged;

        public bool CanExecute(object parameter)
        {
            if (CanExecuteCommand != null)
            {
                return this.CanExecuteCommand(parameter);
            }
            else
            {
                return true;
            }
        }

        public void Execute(object parameter)
        {
            if (this.ExecuteCommand != null)
            {
                this.ExecuteCommand(parameter);
            }
        }

        public void RaiseCanExecuteChanged()
        {
            if (CanExecuteChanged != null)
            {
                CanExecuteChanged(this, EventArgs.Empty);
            }
        }
    }
}

代码中，除了定义StudentViewModel类外，还定义了DelegateCommand类，该类实现了ICommand接口。

ICommand接口中的Execute（）方法用于命令的执行，CanExecute（）方法用于指示当前命令在目标元素上是否可用，当这种可用性发生改变时便会触发接口中的CanExecuteChanged事件。

我们可以将实现了ICommand接口的命令DelegateCommand赋值给Button（命令源）的Command属性（只有实现了ICommandSource接口的元素才拥有该属性），这样Button便与命令进行了绑定。

4 MainWindow.xaml实现

MainWindow.xaml的界面如下图所示。

MainWindow.xaml界面的xaml代码如下所示。

<Window x:Class="WPFMVVMExample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Label Content="学号" Height="28" HorizontalAlignment="Left" Margin="54,23,0,0" Name="labelStudentId" VerticalAlignment="Top" />
        <TextBox Text="{Binding Student.StudentId}" IsReadOnly="True" Height="23" HorizontalAlignment="Right" Margin="0,27,289,0" Name="textBoxStudentId" VerticalAlignment="Top" Width="120" />
        <Label Content="姓名" Height="28" HorizontalAlignment="Left" Margin="54,61,0,0" Name="labelStudentName" VerticalAlignment="Top" />
        <TextBox Text="{Binding Student.StudentName}" IsReadOnly="True" Height="23" HorizontalAlignment="Left" Margin="94,65,0,0" Name="textBoxStudentName" VerticalAlignment="Top" Width="120" />
        <Label Content="年龄" Height="28" HorizontalAlignment="Left" Margin="54,94,0,0" Name="labelStudentAge" VerticalAlignment="Top" />
        <TextBox Text="{Binding Student.StudentAge}" IsReadOnly="True" Height="23" HorizontalAlignment="Left" Margin="94,99,0,0" Name="textBoxStudentAge" VerticalAlignment="Top" Width="120" />
        <Label Content="Email" Height="28" HorizontalAlignment="Left" Margin="50,138,0,0" Name="labelStudentEmail" VerticalAlignment="Top" />
        <TextBox Text="{Binding Student.StudentEmail}" IsReadOnly="True" Height="23" HorizontalAlignment="Left" Margin="94,141,0,0" Name="textBoxStudentEmail" VerticalAlignment="Top" Width="120" />
        <Label Content="性别" Height="28" HorizontalAlignment="Left" Margin="57,176,0,0" Name="labelStudentSex" VerticalAlignment="Top" />
        <TextBox Text="{Binding Student.StudentSex}" IsReadOnly="True" Height="23" HorizontalAlignment="Left" Margin="94,180,0,0" Name="textBoxStudentSex" VerticalAlignment="Top" Width="120" />
        <Button Command="{Binding ShowCommand}" Content="显示" Height="23" HorizontalAlignment="Left" Margin="345,27,0,0" Name="buttonShow" VerticalAlignment="Top" Width="75" />
    </Grid>
</Window>

MainWindow.xaml的后端代码如下所示。

using System.Windows;
using WPFMVVMExample.ViewModel;

namespace WPFMVVMExample
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            this.DataContext = new StudentViewModel();
        }
    }
}

5 运行程序

运行程序，点击“显示”按钮，即将数据绑定至界面显示。

6 说明

WPF中使用MVVM可以降低UI显示与后端逻辑代码的耦合度，即更换界面时，只需要修改很少的逻辑代码就可以实现，甚至不用修改。

在WinForm开发中，我们一般会直接操作界面的元素（如：TextBox1.Text=“aaa”），这样一来，界面变化后，后端逻辑代码也需要做相应的变更。

在WPF中使用数据绑定机制，当数据变化后，数据会通知界面变更的发生，而不需要通过访问界面元素来修改值，这样在后端逻辑代码中也就不必操作或者很少操作界面的元素了。

使用MVVM，可以很好的配合WPF的数据绑定机制来实现UI与逻辑代码的分离，MVVM中的View表示界面，负责页面显示，ViewModel负责逻辑处理，包括准备绑定的数据和命令，ViewModel通过View的DataContext属性绑定至View，Model为业务模型，供ViewModel使用。