C# Zip文件下载解压报错：System.IO.InvalidDataException求助

我在使用C#代码下载并解压Zip文件时遇到问题，触发System.IO.InvalidDataException异常，错误提示为“End of Central Directory record could not be found”。一开始以为是Google Drive的问题，换成Dropbox后问题依旧。

以下是我使用的代码：

private void InstallGameFiles(bool _isUpdate, Version _onlineVersion)
{
    try
    {
        WebClient webClient = new WebClient();

        if (_isUpdate)
        {
            Status = LauncherStatus.downloadingUpdate;
        }
        else
        {
            Status = LauncherStatus.downloadingGame;
            _onlineVersion = new Version(webClient.DownloadString("https://www.dropbox.com/scl/fi/9wc1btx28iz03rr3r6gkt/Version.txt?rlkey=67mgp885v82m9qdafan1se469&st=h7lchvjt&dl=0"));
        }

        webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(DownloadGameCompletedCallback);
        webClient.DownloadFileAsync(new Uri("https://www.dropbox.com/scl/fi/3evjysl179fjrnvxx9uu8/Build.zip?rlkey=c1rcmm7qd0n95whwmc2c2inos&st=yntg8128&dl=0"), gameZip, _onlineVersion);
    }
    catch (Exception ex)
    {
        Status = LauncherStatus.failed;
        MessageBox.Show($"Error installing game files: {ex}");
    }
}

private void DownloadGameCompletedCallback(object sender, AsyncCompletedEventArgs e)
{
    try
    {
        string onlineVersion = ((Version)e.UserState).ToString();
        ZipFile.ExtractToDirectory(gameZip, rootPath, true);
        File.Delete(gameZip);

        File.WriteAllText(versionFile, onlineVersion);

        VersionText.Text = onlineVersion;
        Status = LauncherStatus.ready;
    }
    catch (Exception ex)
    {
        Status = LauncherStatus.failed;
        MessageBox.Show($"Error downloading: {ex}");
    }
}

我原本期望Zip文件能正常下载并解压，已尝试使用Windows默认Zip系统，还更换了存储平台，但仍持续出现该错误。

问题根源 #

你使用的Dropbox链接参数为dl=0，这个参数会返回网页预览页面，而非直接下载Zip文件本身。你实际下载的是一个HTML文件，自然无法被识别为合法的Zip格式，因此触发解压错误。

修复步骤 #

1. 修改下载链接参数：将所有Dropbox链接末尾的dl=0改为dl=1，这是Dropbox的直接下载参数。
2. 同步修复Version.txt链接：获取版本号的Version.txt链接同样使用了dl=0，需一并修改，否则会下载HTML页面导致版本解析失败。

修复后的代码示例 #

private void InstallGameFiles(bool _isUpdate, Version _onlineVersion)
{
    try
    {
        WebClient webClient = new WebClient();

        if (_isUpdate)
        {
            Status = LauncherStatus.downloadingUpdate;
        }
        else
        {
            Status = LauncherStatus.downloadingGame;
            // 修改Version.txt链接的dl参数为1
            _onlineVersion = new Version(webClient.DownloadString("https://www.dropbox.com/scl/fi/9wc1btx28iz03rr3r6gkt/Version.txt?rlkey=67mgp885v82m9qdafan1se469&st=h7lchvjt&dl=1"));
        }

        webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(DownloadGameCompletedCallback);
        // 修改Build.zip链接的dl参数为1
        webClient.DownloadFileAsync(new Uri("https://www.dropbox.com/scl/fi/3evjysl179fjrnvxx9uu8/Build.zip?rlkey=c1rcmm7qd0n95whwmc2c2inos&st=yntg8128&dl=1"), gameZip, _onlineVersion);
    }
    catch (Exception ex)
    {
        Status = LauncherStatus.failed;
        MessageBox.Show($"Error installing game files: {ex}");
    }
}

private void DownloadGameCompletedCallback(object sender, AsyncCompletedEventArgs e)
{
    try
    {
        // 先检查异步下载是否出错
        if (e.Error != null)
        {
            Status = LauncherStatus.failed;
            MessageBox.Show($"Download error: {e.Error.Message}");
            return;
        }
        
        string onlineVersion = ((Version)e.UserState).ToString();
        ZipFile.ExtractToDirectory(gameZip, rootPath, true);
        File.Delete(gameZip);

        File.WriteAllText(versionFile, onlineVersion);

        VersionText.Text = onlineVersion;
        Status = LauncherStatus.ready;
    }
    catch (Exception ex)
    {
        Status = LauncherStatus.failed;
        MessageBox.Show($"Error extracting files: {ex}");
    }
}

额外优化建议 #

• 在DownloadGameCompletedCallback中优先检查e.Error，提前处理下载阶段的错误，避免进入无效的解压流程。
• 可添加文件大小校验逻辑，对比下载后文件的大小与服务器返回的Content-Length，确保文件下载完整。

内容的提问来源于stack exchange，提问作者Rooster Rich