1.10. C# 编程实例

1.10.1. 实例一：文件批量重命名工具

BatchRename.cs

using System.Text.RegularExpressions;

public static class BatchRename
{
    /// <summary>
    /// 批量重命名文件
    /// </summary>
    /// <param name="directory">目标目录</param>
    /// <param name="pattern">搜索模式 如 "*.txt"</param>
    /// <param name="replaceFunc">重命名函数</param>
    /// <returns>重命名的文件数量</returns>
    public static int RenameFiles(
        string directory,
        string pattern,
        Func<string, string> replaceFunc)
    {
        var files = Directory.GetFiles(directory, pattern);
        int count = 0;

        foreach (var filePath in files)
        {
            var dir = Path.GetDirectoryName(filePath)!;
            var fileName = Path.GetFileName(filePath);
            var newName = replaceFunc(fileName);

            if (newName != fileName)
            {
                var newPath = Path.Combine(dir, newName);
                File.Move(filePath, newPath);
                count++;
                Console.WriteLine($"重命名: {fileName} -> {newName}");
            }
        }

        return count;
    }
}

// 使用示例
// 添加前缀："IMG_" + 原文件名
BatchRename.RenameFiles(@"C:\Photos", "*.jpg",
    name => $"IMG_{name}");

// 替换空格为下划线
BatchRename.RenameFiles(@"C:\Docs", "*.pdf",
    name => name.Replace(" ", "_"));

// 序号重命名（正则匹配）
int seq = 1;
BatchRename.RenameFiles(@"C:\Data", "*.csv",
    name => $"{seq++:D4}_{name}");

1.10.2. 实例二：日志分析工具

LogParser.cs

public class LogEntry
{
    public DateTime Timestamp { get; set; }
    public string Level { get; set; } = "";
    public string Message { get; set; } = "";
    public string? Source { get; set; }
}

public class LogParser
{
    private static readonly Regex LogPattern = new(
        @"^\[(?<time>.*?)\]\s\[(?<level>\w+)\]\s(?<message>.*)$",
        RegexOptions.Compiled);

    public async IAsyncEnumerable<LogEntry> ParseAsync(
        string filePath,
        [EnumeratorCancellation] CancellationToken ct = default)
    {
        await foreach (var line in File.ReadLinesAsync(filePath, ct))
        {
            ct.ThrowIfCancellationRequested();

            var match = LogPattern.Match(line);
            if (match.Success)
            {
                yield return new LogEntry
                {
                    Timestamp = DateTime.Parse(match.Groups["time"].Value),
                    Level = match.Groups["level"].Value,
                    Message = match.Groups["message"].Value,
                };
            }
        }
    }

    public async Task<LogSummary> AnalyzeAsync(
        string filePath, CancellationToken ct = default)
    {
        var summary = new LogSummary();

        await foreach (var entry in ParseAsync(filePath, ct))
        {
            summary.Total++;

            if (!summary.LevelCount.ContainsKey(entry.Level))
                summary.LevelCount[entry.Level] = 0;
            summary.LevelCount[entry.Level]++;

            if (entry.Level == "ERROR")
                summary.Errors.Add(entry);
        }

        return summary;
    }
}

public class LogSummary
{
    public int Total { get; set; }
    public Dictionary<string, int> LevelCount { get; set; } = new();
    public List<LogEntry> Errors { get; set; } = new();

    public void PrintReport()
    {
        Console.WriteLine($"总计日志数: {Total}");
        Console.WriteLine($"错误数: {Errors.Count}");
        Console.WriteLine("\n级别统计:");

        foreach (var (level, count) in LevelCount
            .OrderByDescending(x => x.Value))
        {
            var bar = new string('#', count * 40 / Total);
            Console.WriteLine($"  {level,-12} {count,6}  {bar}");
        }
    }
}

1.10.3. 实例三：MVVM 待办事项应用（WPF）

1.10.3.1. Model

public class TodoItem
{
    public int Id { get; set; }
    public string Title { get; set; } = "";
    public bool IsCompleted { get; set; }
    public DateTime CreatedAt { get; set; } = DateTime.Now;
    public Priority Priority { get; set; } = Priority.Medium;
}

public enum Priority { Low, Medium, High }

1.10.3.2. ViewModel

public class TodoViewModel : ViewModelBase
{
    private readonly ObservableCollection<TodoItem> _items = new();

    public ObservableCollection<TodoItem> Items => _items;

    private string _newItemTitle = "";
    public string NewItemTitle
    {
        get => _newItemTitle;
        set
        {
            SetProperty(ref _newItemTitle, value);
            AddCommand.RaiseCanExecuteChanged();
        }
    }

    private TodoItem? _selectedItem;
    public TodoItem? SelectedItem
    {
        get => _selectedItem;
        set => SetProperty(ref _selectedItem, value);
    }

    public IEnumerable<TodoItem> PendingItems
        => Items.Where(i => !i.IsCompleted);

    public IEnumerable<TodoItem> CompletedItems
        => Items.Where(i => i.IsCompleted);

    public RelayCommand AddCommand { get; }
    public RelayCommand<TodoItem> ToggleCommand { get; }
    public RelayCommand<TodoItem> DeleteCommand { get; }

    public TodoViewModel()
    {
        AddCommand = new RelayCommand(
            execute: _ =>
            {
                Items.Add(new TodoItem
                {
                    Id = Items.Count + 1,
                    Title = NewItemTitle,
                    Priority = Priority.Medium
                });
                NewItemTitle = "";
            },
            canExecute: _ => !string.IsNullOrWhiteSpace(NewItemTitle));

        ToggleCommand = new RelayCommand<TodoItem>(
            execute: item =>
            {
                item.IsCompleted = !item.IsCompleted;
                OnPropertyChanged(nameof(PendingItems));
                OnPropertyChanged(nameof(CompletedItems));
            });

        DeleteCommand = new RelayCommand<TodoItem>(
            execute: item =>
            {
                Items.Remove(item);
            });
    }
}

1.10.3.3. View（MainWindow.xaml）

<Window x:Class="TodoApp.MainWindow"
        Title="待办事项" Height="450" Width="500">
    <Grid Margin="12">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <!-- 添加新任务 -->
        <StackPanel Orientation="Horizontal" Grid.Row="0"
                    Margin="0,0,0,12">
            <TextBox Text="{Binding NewItemTitle}"
                     Width="350" PlaceholderText="输入新任务..."/>
            <Button Content="添加" Command="{Binding AddCommand}"
                    Width="80" Margin="10,0,0,0"/>
        </StackPanel>

        <!-- 任务列表 -->
        <ListBox Grid.Row="1"
                 ItemsSource="{Binding Items}"
                 SelectedItem="{Binding SelectedItem}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Horizontal">
                        <CheckBox IsChecked="{Binding IsCompleted}"
                                  Command="{Binding
                              DataContext.ToggleCommand,
                              RelativeSource={RelativeSource
                              AncestorType=Window}}"
                                  CommandParameter="{Binding}"/>
                        <TextBlock Text="{Binding Title}"
                                   FontSize="14"
                                   TextDecorations="{Binding IsCompleted,
                                       Converter={StaticResource StrikeConverter}}"
                                   Margin="8,0"/>
                        <TextBlock Text="{Binding Priority}"
                                   Foreground="Gray" FontSize="12"/>
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

        <!-- 统计信息 -->
        <TextBlock Grid.Row="2" Margin="0,12,0,0">
            <Run Text="总计:"/><Run Text="{Binding Items.Count}"/>
            <Run Text=" 已完成:"/>
            <Run Text="{Binding CompletedItems.Count}"/>
            <Run Text=" 待完成:"/>
            <Run Text="{Binding PendingItems.Count}"/>
        </TextBlock>
    </Grid>
</Window>