WPF MVVM模式的登录界面及代码

以下是一个简单的WPF MVVM模式的登录界面及代码：

XAML代码：

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApp1"
        Title="Login" Height="250" Width="350">
    <Window.DataContext>
        <local:LoginViewModel />
    </Window.DataContext>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <Label Grid.Row="0" Grid.Column="0" Content="Username:"/>
        <TextBox Grid.Row="0" Grid.Column="1" Width="200" Margin="5" Text="{Binding Username}" />
        <Label Grid.Row="1" Grid.Column="0" Content="Password:"/>
        <PasswordBox Grid.Row="1" Grid.Column="1" Width="200" Margin="5" Password="{Binding Password}" />
        <Button Grid.Row="2" Grid.Column="1" Width="100" Margin="5" Content="Login" Command="{Binding LoginCommand}" IsDefault="True"/>
        <Label Grid.Row="3" Grid.Column="1" Content="{Binding ErrorMessage}" Foreground="Red" HorizontalAlignment="Center"/>
        <CheckBox Grid.Row="4" Grid.Column="1" Content="Remember Me" Margin="5" IsChecked="{Binding RememberMe}"/>
    </Grid>
</Window>

ViewModel代码：

using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows;
using System.Windows.Input;

namespace WpfApp1
{
    public class LoginViewModel : INotifyPropertyChanged
    {
        private string _username;
        private string _password;
        private bool _rememberMe;
        private string _errorMessage;

        public string Username
        {
            get { return _username; }
            set { _username = value; OnPropertyChanged(); }
        }

        public string Password
        {
            get { return _password; }
            set { _password = value; OnPropertyChanged(); }
        }

        public bool RememberMe
        {
            get { return _rememberMe; }
            set { _rememberMe = value; OnPropertyChanged(); }
        }

        public string ErrorMessage
        {
            get { return _errorMessage; }
            set { _errorMessage = value; OnPropertyChanged(); }
        }

        public ICommand LoginCommand { get; set; }

        public LoginViewModel()
        {
            LoginCommand = new RelayCommand(Login, CanLogin);
        }

        private bool CanLogin()
        {
            return !string.IsNullOrEmpty(Username) && !string.IsNullOrEmpty(Password);
        }

        private void Login()
        {
            if (Username == "admin" && Password == "password")
            {
                if (RememberMe)
                {
                    // Save login information to file or database
                }
                MessageBox.Show("Login successful!");
            }
            else
            {
                ErrorMessage = "Invalid username or password";
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

其中，`RelayCommand`是一个实现了`ICommand`接口的自定义命令类，用于绑定按钮的点击事件。你可以在网上找到相关实现代码。