1. 程式截圖

2.程式的結構圖

3.說明：
如圖2所示，Model中存放的是User類檔案

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

namespace WpfApp.Model
{
   public class User
    {
       public string UserName { get; set; }
       public int UserId { get; set; }
       public string Password { get
 
; set; }
    }
}

ViewModel

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Windows.Input;
using WpfApp.Model;
using WpfApp.Command;
using System.Windows;


namespace WpfApp.ViewModel
{
    public
 
 class UserViewModel : INotifyPropertyChanged
    {
        #region 私有欄位
        private string userName;

        private string userPassword;

        private ICommand loginCommand;

        private User user = new User(); 
        #endregion
        #region 屬性
        public ICommand LoginCommand
        {
            get
 
 { return loginCommand; }
        }
        public string UserName
        {
            get
            {
                return userName;
            }
            set
            {
                this.userName = value;
                if (this.PropertyChanged != null)
                {
                    this.PropertyChanged(this, new PropertyChangedEventArgs("UserName"));
                }
            }
        }

        public string UserPassword
        {
            get
            {
                return userPassword;
            }
            set
            {
                this.userPassword = value;
                if (this.PropertyChanged != null)
                {
                    this.PropertyChanged(this, new PropertyChangedEventArgs("UserPassword"));
                }
            }
        } 
        #endregion

        public UserViewModel()
        {
            user.UserId = 1;
            user.UserName = "huangxi";
            user.Password = "123";
            loginCommand = new LoginCommand(this);
        }

        #region 公共方法
        public void QueryData()
        {
            if (!string.IsNullOrEmpty(this.UserName))
            {
                if (this.UserName != user.UserName)
                {
                    return;
                }
                if (this.UserPassword != user.Password)
                {
                    return;
                }
                MessageBox.Show("登入成功");
            }
        } 
        #endregion
        #region INotifyPropertyChanged成員
        public event PropertyChangedEventHandler PropertyChanged;
        #endregion
    }
}

還有Command，存放的是Command,實現了ICommand介面

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Input;
using WpfApp.ViewModel;

namespace WpfApp.Command
{
    public class LoginCommand:ICommand
    {
        private UserViewModel userViewModel;
        #region ICommand成員
        public bool CanExecute(object parameter)
        {
            return true;
        }

        public event EventHandler CanExecuteChanged;

        public void Execute(object parameter)
        {
            userViewModel.QueryData();
        } 
        #endregion

        public LoginCommand(UserViewModel userViewModel)
        {
            this.userViewModel = userViewModel;
        }
    }
}

最後是View層，

<Window x:Class="WpfApp.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="使用者名稱" HorizontalAlignment="Left" Margin="73,80,0,0" VerticalAlignment="Top"/>
        <Label Content="密碼" HorizontalAlignment="Left" Margin="73,138,0,0" VerticalAlignment="Top" RenderTransformOrigin="0.798,-0.492"/>
        <Button Content="BtnLogin" HorizontalAlignment="Left" Margin="229,221,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click"/>
        <TextBox  x:Name ="txtUserName" HorizontalAlignment="Left" Height="23" Margin="203,80,0,0" TextWrapping="Wrap"  VerticalAlignment="Top" Width="120" Text="{Binding UserName,Mode=TwoWay}"/>

        <TextBox x:Name="txtPassword" HorizontalAlignment="Left" Height="23" Margin="203,141,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120" Text="{Binding UserPassword,Mode=TwoWay}"/>

    </Grid>
</Window>

這裡有一個問題，因為預設的Password沒法繫結，這裡採用的TextBox代替，網路上有很多Password的幫助類，有興趣的同學可以自行百度。

介面層的後臺程式碼

using System.Windows;
using WpfApp.ViewModel;

namespace WpfApp
{
    /// <summary>
    /// MainWindow.xaml 的互動邏輯
    /// </summary>
    public partial class MainWindow : Window
    {
        private UserViewModel userViewModel = null;
        public MainWindow()
        {
            InitializeComponent();
            userViewModel = new UserViewModel();
            this.DataContext = userViewModel;
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {

            if (this.userViewModel != null)
            {
                this.userViewModel.UserName = this.txtUserName.Text;
                this.userViewModel.UserPassword = this.txtPassword.Text;
                this.userViewModel.LoginCommand.Execute(null);
            }
        }
    }
}

到這裡就結束了。