C#写差异文件备份工具的示例

下面详细讲解“C#写差异文件备份工具的示例”的完整攻略。

1. 确定需求和技术方案

在开始开发前，我们需要明确这个备份工具的需求和技术方案。这个备份工具需要通过比对源文件和目标文件的差异，只保留源文件中的新增、修改、删除等操作，实现对文件的备份。

技术方案可以借助Git等版本控制工具的基本原理来实现。通过计算文件内容的hash值，比较源文件和目标文件的hash值，来判断文件是否有变化，并记录变化类型和内容，最后将记录的差异应用到备份文件中。

2. 实现文件比对功能

前置条件：安装Git for Windows，添加Git命令行工具到环境变量PATH中。

下面以C#语言为例，介绍如何实现基于Git的文件比对功能：

2.1 创建文件差异类

public class FileDiff
{
    public enum ChangeType
    {
        None,
        Modified,
        Added,
        Deleted
    }

    public string Path;
    public ChangeType Change;
    public string Content;

    public FileDiff()
    {
        Change = ChangeType.None;
    }
}

2.2 创建Git工具类，计算文件内容的hash值

public class GitUtility
{
    public static string GetHash(string path)
    {
        var result = RunCommand($"hash-object -t blob '{path}'");
        if (result.ExitCode != 0)
        {
            throw new Exception(result.Errors);
        }

        return result.Output.Trim();
    }

    private static ProcessResult RunCommand(string command)
    {
        using (var process = new Process())
        {
            process.StartInfo.FileName = "git";
            process.StartInfo.Arguments = command;
            process.StartInfo.UseShellExecute = false;
            process.StartInfo.RedirectStandardOutput = true;
            process.StartInfo.RedirectStandardError = true;
            process.Start();

            var output = process.StandardOutput.ReadToEnd();
            var errors = process.StandardError.ReadToEnd();

            process.WaitForExit();

            return new ProcessResult
            {
                ExitCode = process.ExitCode,
                Output = output,
                Errors = errors
            };
        }
    }

    private class ProcessResult
    {
        public int ExitCode { get; set; }
        public string Output { get; set; }
        public string Errors { get; set; }
    }
}

2.3 实现文件比对功能，记录差异文件并返回

public class FileBackup
{
    private IList<FileDiff> _fileDiffs = new List<FileDiff>();

    public IEnumerable<FileDiff> Backup(string sourcePath, string targetPath)
    {
        var sourceFiles = Directory.GetFiles(sourcePath, "*.*", SearchOption.AllDirectories);
        var targetFiles = Directory.GetFiles(targetPath, "*.*", SearchOption.AllDirectories);

        foreach (var sourceFile in sourceFiles)
        {
            var relativePath = GetFilePathRelativeTo(sourceFile, sourcePath);
            var targetFile = Path.Combine(targetPath, relativePath);

            if (!File.Exists(targetFile))
            {
                _fileDiffs.Add(new FileDiff
                {
                    Path = relativePath,
                    Change = FileDiff.ChangeType.Added,
                    Content = File.ReadAllText(sourceFile)
                });
            }
            else
            {
                var sourceContent = GitUtility.GetHash(sourceFile);
                var targetContent = GitUtility.GetHash(targetFile);

                if (sourceContent == targetContent)
                {
                    continue;
                }

                _fileDiffs.Add(new FileDiff
                {
                    Path = relativePath,
                    Change = FileDiff.ChangeType.Modified,
                    Content = GitUtility.RunCommand($"diff {sourceFile} {targetFile}").Output
                });
            }
        }

        foreach (var targetFile in targetFiles)
        {
            var relativePath = GetFilePathRelativeTo(targetFile, targetPath);
            var sourceFile = Path.Combine(sourcePath, relativePath);

            if (!File.Exists(sourceFile))
            {
                _fileDiffs.Add(new FileDiff
                {
                    Path = relativePath,
                    Change = FileDiff.ChangeType.Deleted
                });
            }
        }

        return _fileDiffs;
    }

    private string GetFilePathRelativeTo(string path, string basePath)
    {
        return Path.GetRelativePath(basePath, path);
    }
}

3. 使用示例

下面分别以控制台应用程序和WinForms应用程序为例，演示如何使用C#开发的差异文件备份工具。

3.1 控制台应用程序

static void Main(string[] args)
{
    var backup = new FileBackup();
    var diffs = backup.Backup(@"C:\source", @"D:\target");

    foreach (var diff in diffs)
    {
        Console.WriteLine($"[{diff.Change}] {diff.Path}");

        if (diff.Change == FileDiff.ChangeType.Modified)
        {
            Console.WriteLine(diff.Content);
        }
    }

    Console.ReadKey();
}

3.2 WinForms应用程序

public partial class MainForm : Form
{
    public MainForm()
    {
        InitializeComponent();
    }

    private void buttonBackup_Click(object sender, EventArgs e)
    {
        var backup = new FileBackup();
        var diffs = backup.Backup(textboxSourcePath.Text, textboxTargetPath.Text);

        listviewFileDiffs.Items.Clear();

        foreach (var diff in diffs)
        {
            var item = new ListViewItem(diff.Path);
            item.SubItems.Add(diff.Change.ToString());

            if (diff.Change == FileDiff.ChangeType.Modified)
            {
                item.SubItems.Add(diff.Content);
            }

            listviewFileDiffs.Items.Add(item);
        }
    }
}