WPF MVVM 入门示例讲解

M-V-VM是Model-View-ViewModel的简写，Model，ViewModel是个类文件（.cs文件)，View是前台文件（,xaml文件）。假设我们的工程只有一个前台文件和一个后台文件，当设计要求越来越多的时候，前后台文件可能会高达上千行，甚至上万行，此时要想找到对应的代码，鼠标滚轮会滑的头大。学习MVVM便于工程调试，修改，移植。用MVVM如果只是修改或者更好显示界面，后台文件只需稍微的改动甚至不用改动。下面这个例子是V-VM模式就是view和viewmodel，先以简单的入门，工程集如下：

 

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<Window x:Class="Students.View"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Students"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>

        <Grid.RowDefinitions>
            <RowDefinition Height="30"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid x:Name ="StudetGrid"  Grid.Row ="0">
            <Grid.DataContext>
                <!--声明创建一个ViewModel的实例,这个声明确定了ViewModel.cs是VM,这个声明建立了View.xaml与ViemModel之间的桥梁，这个myGrid所有绑定的属性(Name,Age,Sex)都值的是ViewModel.cs类中的成员-->
                <local:StudetViewModel/>
            </Grid.DataContext>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <TextBlock Text="姓名：" Grid.Column="0" HorizontalAlignment="Right"/>
            <TextBlock Text="{Binding Name}" Grid.Column="1"/>
            <TextBlock Text="年龄：" Grid.Column="2" HorizontalAlignment="Right"  />
            <TextBlock Text="{Binding Age}" Grid.Column="3" />
            <TextBlock Text="性别：" Grid.Column="4" HorizontalAlignment="Right" />
            <TextBlock Text="{Binding Sex}" Grid.Column="5"/>
            <Button Content="更新" Grid.Column="6" Click="BtnClick" />

        </Grid>
    </Grid>
</Window>
View.xaml
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace Students
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class View : Window
    {
        public static StudetViewModel viewModel;//声明一个类，但是没有实例化,把这个viewModel设为static方便其他页面文件互相访问绑定的属性
        public View()
        {
            InitializeComponent();
            viewModel = StudetGrid.DataContext as StudetViewModel;//在构造方法中实例化viewModel，这个viewModel就是View.xaml中声明的那个ViewModel实例，就是那个桥梁。
        }

        private void BtnClick(object sender, RoutedEventArgs e)
        {
            viewModel.Name = "小明";
            viewModel.Age = "15";
            viewModel.Sex = "男";
        }
    }
}
View.xaml.cs
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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;

namespace Students
{
    public class StudetViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        private string name;
        public String Name
        {
            get { return name; }
            set { name = value; OnPropertyChanged("Name"); }
        }

        private string age;
        public String Age
        {
            get { return age; }
            set { age = value; OnPropertyChanged("Age"); }
        }

        private string sex;
        public String Sex
        {
            get { return sex; }
            set { sex = value; OnPropertyChanged("Sex"); }
        }
    }
}
StudetViewModel.cs
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View.xaml是View，那如何确定StudetViewModel.cs就是VM呢？在View.xaml文件中有如下声明

 

 在前台文件中声明数据上下文指定类，指定的那个类就是ViewModel。先看一下运行效果吧

 

 

 

 这个工程文件里的StudetViewModel.cs其实就是Model和ViewModel合在一起了

 

 增加完Model类后的程序集如下：

 

 如何确定PeronModel就Model呢？因为它在ViewModel中有实例化

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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;

namespace Students
{
    public class StudetViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }


        private PersonModel _studentModel = new PersonModel();//实例化Model中的类
        public PersonModel StudentModel
        {
            get { return _studentModel; }
            set { _studentModel = value; OnPropertyChanged("StudentModel"); }
        }
    }
}
StudetViewModel
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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;

namespace Students
{
    public class PersonModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        private string name;
        public String Name
        {
            get { return name; }
            set { name = value; OnPropertyChanged("Name"); }
        }

        private string age;
        public String Age
        {
            get { return age; }
            set { age = value; OnPropertyChanged("Age"); }
        }

        private string sex;
        public String Sex
        {
            get { return sex; }
            set { sex = value; OnPropertyChanged("Sex"); }
        }
    }
}
Students
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<Window x:Class="Students.View"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Students"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>

        <Grid.RowDefinitions>
            <RowDefinition Height="30"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid x:Name ="StudetGrid"  Grid.Row ="0">
            <Grid.DataContext>
                <!--声明创建一个ViewModel的实例,这个声明确定了ViewModel.cs是VM,这个声明建立了View.xaml与ViemModel之间的桥梁，这个myGrid所有绑定的属性(Name,Age,Sex)都值的是ViewModel.cs类中的成员-->
                <local:StudetViewModel/>
            </Grid.DataContext>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <TextBlock Text="姓名：" Grid.Column="0" HorizontalAlignment="Right"/>
            <TextBlock Text="{Binding StudentModel.Name}" Grid.Column="1"/>
            <TextBlock Text="年龄：" Grid.Column="2" HorizontalAlignment="Right"  />
            <TextBlock Text="{Binding StudentModel.Age}" Grid.Column="3" />
            <TextBlock Text="性别：" Grid.Column="4" HorizontalAlignment="Right" />
            <TextBlock Text="{Binding StudentModel.Sex}" Grid.Column="5"/>
            <Button Content="更新" Grid.Column="6" Click="BtnClick" />

        </Grid>
    </Grid>
</Window>
View
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace Students
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class View : Window
    {
        public static StudetViewModel viewModel;//声明一个类，但是没有实例化,把这个viewModel设为static方便其他页面文件互相访问绑定的属性
        public View()
        {
            InitializeComponent();
            viewModel = StudetGrid.DataContext as StudetViewModel;//在构造方法中实例化viewModel，这个viewModel就是View.xaml中声明的那个ViewModel实例，就是那个桥梁。
        }

        private void BtnClick(object sender, RoutedEventArgs e)
        {
            viewModel.StudentModel.Name = "小明";
            viewModel.StudentModel.Age = "15";
            viewModel.StudentModel.Sex = "男";
        }
    }
}
View.xaml.cs
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View中实例化过ViewModel，而ViewModel中实例化过Model，所以说ViewModel建立起了View与Model之间沟通的桥梁。一个ViewModel类中可以有多个不同的Model类的实例，比如我们还可以创建一个成绩类（Model）,然后在ViewModel中去实例化，最后在View界面中去绑定各科成绩，这个好理解。

View中也可以实例化多个ViewModel

程序集如下：

 

 

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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;

namespace Students
{
    public class TeacherViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }


        private PersonModel _teacherModel = new PersonModel();//实例化Model中的类
        public PersonModel TeacherModel
        {
            get { return _teacherModel; }
            set { _teacherModel = value; OnPropertyChanged("TeacherModel"); }
        }
    }
}
TeacherViewModel
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<Window x:Class="Students.View"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Students"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>

        <Grid.RowDefinitions>
            <RowDefinition Height="30"/>
            <RowDefinition Height="30"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid x:Name ="StudetGrid"  Grid.Row ="0">
            <Grid.DataContext>
                <!--声明创建一个ViewModel的实例,这个声明确定了ViewModel.cs是VM,这个声明建立了View.xaml与ViemModel之间的桥梁，这个myGrid所有绑定的属性(Name,Age,Sex)都值的是ViewModel.cs类中的成员-->
                <local:StudetViewModel/>
            </Grid.DataContext>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <TextBlock Text="学生姓名：" Grid.Column="0" HorizontalAlignment="Right"/>
            <TextBlock Text="{Binding StudentModel.Name}" Grid.Column="1"/>
            <TextBlock Text="年龄：" Grid.Column="2" HorizontalAlignment="Right"  />
            <TextBlock Text="{Binding StudentModel.Age}" Grid.Column="3" />
            <TextBlock Text="性别：" Grid.Column="4" HorizontalAlignment="Right" />
            <TextBlock Text="{Binding StudentModel.Sex}" Grid.Column="5"/>
            <Button Content="更新" Grid.Column="6" Click="BtnClick" />

        </Grid>
        <Grid x:Name ="TeacherGrid"  Grid.Row ="1">
            <Grid.DataContext>
                <!--声明创建一个ViewModel的实例,这个声明确定了ViewModel.cs是VM,这个声明建立了View.xaml与ViemModel之间的桥梁，这个myGrid所有绑定的属性(Name,Age,Sex)都值的是ViewModel.cs类中的成员-->
                <local:TeacherViewModel/>
            </Grid.DataContext>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <TextBlock Text="老师姓名：" Grid.Column="0" HorizontalAlignment="Right"/>
            <TextBlock Text="{Binding TeacherModel.Name}" Grid.Column="1"/>
            <TextBlock Text="年龄：" Grid.Column="2" HorizontalAlignment="Right"  />
            <TextBlock Text="{Binding TeacherModel.Age}" Grid.Column="3" />
            <TextBlock Text="性别：" Grid.Column="4" HorizontalAlignment="Right" />
            <TextBlock Text="{Binding TeacherModel.Sex}" Grid.Column="5"/>
            <Button Content="更新" Grid.Column="6" Click="BtnClickTeacher" />

        </Grid>
    </Grid>
</Window>
View.xaml
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace Students
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class View : Window
    {
        public static StudetViewModel studentViewModel;//声明一个类，但是没有实例化,把这个viewModel设为static方便其他页面文件互相访问绑定的属性
        public static TeacherViewModel teacherViewModel;
        public View()
        {
            InitializeComponent();
            studentViewModel = StudetGrid.DataContext as StudetViewModel;//在构造方法中实例化viewModel，这个viewModel就是View.xaml中声明的那个ViewModel实例，就是那个桥梁。
            teacherViewModel = TeacherGrid.DataContext as TeacherViewModel;
        }

        private void BtnClick(object sender, RoutedEventArgs e)
        {
            studentViewModel.StudentModel.Name = "小明";
            studentViewModel.StudentModel.Age = "15";
            studentViewModel.StudentModel.Sex = "男";
        }

        private void BtnClickTeacher(object sender, RoutedEventArgs e)
        {
            teacherViewModel.TeacherModel.Name = "王老师";
            teacherViewModel.TeacherModel.Age = "30";
            teacherViewModel.TeacherModel.Sex = "女";
        }
    }
}
View.xaml.cs
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效果如下：

 上面的示例中，控件的成员属性和View分开了，但是按键的Click事件内容还是在后台文件实现的，那怎么把事件属性也和View分开呢？

<Button Content="更新" Grid.Column="6" Command="{Binding CommadUpdata}" />
View Code

把Button 的Click用Commad代替，以TeacherViewModel例

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using Prism.Commands;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;

namespace Students
{
    public class TeacherViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }


        private PersonModel _teacherModel = new PersonModel();//实例化Model中的类
        public PersonModel TeacherModel
        {
            get { return _teacherModel; }
            set { _teacherModel = value; OnPropertyChanged("TeacherModel"); }
        }

        public TeacherViewModel()
        {
            this.CommadUpdata = new DelegateCommand(new Action(Updata));//命令属性与方法联系起来
        }

        private void Updata()//方法
        {
            this.TeacherModel.Name = "王老师";
            this.TeacherModel.Age = "30";
            this.TeacherModel.Sex = "女";
        }

        public DelegateCommand CommadUpdata { get; set; }//命令属性
    }
}
TeacherViewModel
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StudentViewModel也是类似，这样改完后，后台文件View.xaml.cs没有添加任何东西

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace Students
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class View : Window
    {
        public View()
        {
            InitializeComponent();
        }
    }
}
View.xaml.cs
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这样成员属性和命令属性都和前台文件去耦合了

 源码下载地址：https://github.com/lizhiqiang0204/WPF_MVVM_Demo

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