WPF MVVM 分页实现：一个简单示例

以下是一个简单的WPF MVVM分页示例：

1. 首先，创建一个名为'PagingViewModel'的ViewModel类，其中包含以下属性和命令：

public class PagingViewModel : INotifyPropertyChanged
{
    private ObservableCollection<string> _items;
    private int _currentPage;
    private int _totalPages;
    private ICommand _previousPageCommand;
    private ICommand _nextPageCommand;

    public ObservableCollection<string> Items
    {
        get { return _items; }
        set
        {
            _items = value;
            OnPropertyChanged(nameof(Items));
        }
    }

    public int CurrentPage
    {
        get { return _currentPage; }
        set
        {
            _currentPage = value;
            OnPropertyChanged(nameof(CurrentPage));
        }
    }

    public int TotalPages
    {
        get { return _totalPages; }
        set
        {
            _totalPages = value;
            OnPropertyChanged(nameof(TotalPages));
        }
    }

    public ICommand PreviousPageCommand
    {
        get { return _previousPageCommand ?? (_previousPageCommand = new RelayCommand(PreviousPage, CanGoToPreviousPage)); }
    }

    public ICommand NextPageCommand
    {
        get { return _nextPageCommand ?? (_nextPageCommand = new RelayCommand(NextPage, CanGoToNextPage)); }
    }

    //Methods for navigating to previous and next pages
    private void PreviousPage()
    {
        CurrentPage--;
        UpdateItems();
    }

    private void NextPage()
    {
        CurrentPage++;
        UpdateItems();
    }

    //Methods for checking if navigation to previous and next pages is possible
    private bool CanGoToPreviousPage()
    {
        return CurrentPage > 1;
    }

    private bool CanGoToNextPage()
    {
        return CurrentPage < TotalPages;
    }

    //Method for updating the collection of items based on the current page number
    private void UpdateItems()
    {
        Items.Clear();
        //TODO: Populate the Items collection based on the current page number
    }

    //INotifyPropertyChanged implementation
    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

2. 在MainWindow.xaml中定义界面布局。这里使用Grid控件来布局，并在其中添加一个ListBox控件来显示分页数据。

<Window x:Class="PagingExample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:PagingExample"
        Title="Paging Example" Height="350" Width="525">
    <Window.DataContext>
        <local:PagingViewModel />
    </Window.DataContext>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <ListBox Grid.Row="0" ItemsSource="{Binding Items}" />
        <StackPanel Grid.Row="1" Orientation="Horizontal" HorizontalAlignment="Center">
            <Button Content="Previous" Command="{Binding PreviousPageCommand}" />
            <TextBlock Text="{Binding CurrentPage}" Margin="5" />
            <Button Content="Next" Command="{Binding NextPageCommand}" />
        </StackPanel>
    </Grid>
</Window>

3. 在ViewModel类的构造函数中初始化分页数据，并计算总页数。

public PagingViewModel()
{
    Items = new ObservableCollection<string>();
    //TODO: Populate the Items collection with initial data

    CurrentPage = 1;
    TotalPages = (int)Math.Ceiling((double)Items.Count / PageSize);
}

4. 在UpdateItems方法中根据当前页码和页大小计算要显示的数据，并更新Items集合。

private void UpdateItems()
{
    Items.Clear();
    int startIndex = (CurrentPage - 1) * PageSize;
    int endIndex = Math.Min(startIndex + PageSize, Items.Count);
    for (int i = startIndex; i < endIndex; i++)
    {
        Items.Add(Items[i]);
    }
}

5. 在RelayCommand类中定义一个简单的ICommand实现。

public class RelayCommand : ICommand
{
    private readonly Action _execute;
    private readonly Func<bool> _canExecute;

    public RelayCommand(Action execute, Func<bool> canExecute = null)
    {
        _execute = execute ?? throw new ArgumentNullException(nameof(execute));
        _canExecute = canExecute;
    }

    public bool CanExecute(object parameter)
    {
        return _canExecute?.Invoke() ?? true;
    }

    public void Execute(object parameter)
    {
        _execute();
    }

    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }
}

6. 最后，在App.xaml.cs中启动应用程序，并在Main方法中设置主窗口。

public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);

        MainWindow mainWindow = new MainWindow();
        mainWindow.Show();
    }
}

这样就完成了一个简单的WPF MVVM分页示例。