目录存在时 ZipFile.ExtractToDirectory 会抛出异常吗？

Question

根据Microsoft Docs，如果要提取zip文件的目标目录已经存在，程序应该抛出IOException。此外，“备注”部分说，“目标目录不能已经存在。”然而，

ZipFile.ExtractToDirectory("archive.zip", ".\\output");

即使output 作为目录存在也可以正常工作（没有例外）。类似的东西

ZipFile.ExtractToDirectory("archive.zip", "\\");

也可以毫无例外地工作。因此，我试图理解为什么在 Microsoft Docs 明确建议应该有例外时没有例外。

注意：我正在运行 .NET 5。

Answer 1

看起来像一个文档错误。我为此打开了两个 GitHub 问题，one for the source code comments 和 one for the docs page 是由它们创建的

.NET Core 是开源的，这意味着我们可以检查实际的源代码以了解发生了什么。

ZipFile.ExtractToDirectory实际上调用了ZipFileExtensions.ExtractToDirectory(ZipArchive, String)方法：

public static void ExtractToDirectory(string sourceArchiveFileName, string destinationDirectoryName, Encoding? entryNameEncoding, bool overwriteFiles)
{
    if (sourceArchiveFileName == null)
        throw new ArgumentNullException(nameof(sourceArchiveFileName));

    using (ZipArchive archive = Open(sourceArchiveFileName, ZipArchiveMode.Read, entryNameEncoding))
    {
        archive.ExtractToDirectory(destinationDirectoryName, overwriteFiles);
    }
}

在the actual code IOException 中不如果目标目录存在则抛出，即使文档网站这么说：

/// <exception cref="IOException">An archive entry?s name is zero-length, contains only whitespace, or contains one or more invalid
/// characters as defined by InvalidPathChars. -or- Extracting an archive entry would have resulted in a destination
/// file that is outside destinationDirectoryName (for example, if the entry name contains parent directory accessors).
/// -or- An archive entry has the same name as an already extracted entry from the same archive.</exception>
public static void ExtractToDirectory(this ZipArchive source, string destinationDirectoryName, bool overwriteFiles)
{
    if (source == null)
        throw new ArgumentNullException(nameof(source));

    if (destinationDirectoryName == null)
        throw new ArgumentNullException(nameof(destinationDirectoryName));

    foreach (ZipArchiveEntry entry in source.Entries)
    {
        entry.ExtractRelativeToDirectory(destinationDirectoryName, overwriteFiles);
    }
}

看起来docs.microsoft.com 位于实际源文档的后面。

为了完整起见，internal ExtractRelativeToDirectory method 明确将现有目标文件夹视为有效案例：

internal static void ExtractRelativeToDirectory(this ZipArchiveEntry source, string destinationDirectoryName, bool overwrite)
{
    if (source == null)
        throw new ArgumentNullException(nameof(source));

    if (destinationDirectoryName == null)
        throw new ArgumentNullException(nameof(destinationDirectoryName));

    // Note that this will give us a good DirectoryInfo even if destinationDirectoryName exists:
    DirectoryInfo di = Directory.CreateDirectory(destinationDirectoryName);
      ...

强调：

// 请注意，即使destinationDirectoryName 存在，这也会为我们提供良好的DirectoryInfo