最准确的方法是使用shlwapi.dll中的一些互操作代码

[DllImport(SHLWAPI, CharSet = CharSet.Unicode)]
[return: MarshalAsAttribute(UnmanagedType.Bool)]
[ResourceExposure(ResourceScope.None)]
internal static extern bool PathIsDirectory([MarshalAsAttribute(UnmanagedType.LPWStr), In] string pszPath);

然后你可以这样调用它:

#region IsDirectory
/// <summary>
/// Verifies that a path is a valid directory.
/// </summary>
/// <param name="path">The path to verify.</param>
/// <returns><see langword="true"/> if the path is a valid directory; 
/// otherwise, <see langword="false"/>.</returns>
/// <exception cref="T:System.ArgumentNullException">
/// <para><paramref name="path"/> is <see langword="null"/>.</para>
/// </exception>
/// <exception cref="T:System.ArgumentException">
/// <para><paramref name="path"/> is <see cref="F:System.String.Empty">String.Empty</see>.</para>
/// </exception>
public static bool IsDirectory(string path)
{
    return PathIsDirectory(path);
}

我在遇到类似的问题时遇到过这个问题，只不过我需要检查一个文件或文件夹的路径是否为文件或文件夹，而该文件或文件夹可能实际上并不存在。上面有一些关于答案的评论，提到它们不适用于这种情况。我找到了一个解决方案(我使用VB。NET，但你可以转换，如果你需要)，这似乎很适合我:

Dim path As String = "myFakeFolder\ThisDoesNotExist\"
Dim bIsFolder As Boolean = (IO.Path.GetExtension(path) = "")
'returns True

Dim path As String = "myFakeFolder\ThisDoesNotExist\File.jpg"
Dim bIsFolder As Boolean = (IO.Path.GetExtension(path) = "")
'returns False

希望这能对别人有所帮助!

这是我的解决方案，注意，我正在寻找一个函数，严格避免任何不必要的文件系统访问，但这里只允许字符串操作(路径可能不存在):

public static bool IsFolder(string path)
{
    if (string.IsNullOrEmpty(path)) return false;
    if (path.EndsWith("\\")) return true;
    return (path.Contains("\\") && string.IsNullOrEmpty(Path.GetExtension(path)));
}

使用这篇文章中所选的答案，我看了评论并给予了信任 @ŞafakGür， @Anthony和@Quinn Wilson，他们的信息让我得到了这个改进的答案，我写了并测试了:

    /// <summary>
    /// Returns true if the path is a dir, false if it's a file and null if it's neither or doesn't exist.
    /// </summary>
    /// <param name="path"></param>
    /// <returns></returns>
    public static bool? IsDirFile(this string path)
    {
        bool? result = null;

        if(Directory.Exists(path) || File.Exists(path))
        {
            // get the file attributes for file or directory
            var fileAttr = File.GetAttributes(path);

            if (fileAttr.HasFlag(FileAttributes.Directory))
                result = true;
            else
                result = false;
        }

        return result;
    }

很晚才到这里，但我发现Nullable<Boolean>返回值相当难看- IsDirectory(字符串路径)返回null并不等于没有详细注释的不存在的路径，所以我提出了以下内容:

public static class PathHelper
{
    /// <summary>
    /// Determines whether the given path refers to an existing file or directory on disk.
    /// </summary>
    /// <param name="path">The path to test.</param>
    /// <param name="isDirectory">When this method returns, contains true if the path was found to be an existing directory, false in all other scenarios.</param>
    /// <returns>true if the path exists; otherwise, false.</returns>
    /// <exception cref="ArgumentNullException">If <paramref name="path"/> is null.</exception>
    /// <exception cref="ArgumentException">If <paramref name="path"/> equals <see cref="string.Empty"/></exception>
    public static bool PathExists(string path, out bool isDirectory)
    {
        if (path == null) throw new ArgumentNullException(nameof(path));
        if (path == string.Empty) throw new ArgumentException("Value cannot be empty.", nameof(path));

        isDirectory = Directory.Exists(path);

        return isDirectory || File.Exists(path);
    }
}

这个helper方法写得足够冗长和简洁，以便在第一次阅读时就能理解其意图。

/// <summary>
/// Example usage of <see cref="PathExists(string, out bool)"/>
/// </summary>
public static void Usage()
{
    const string path = @"C:\dev";

    if (!PathHelper.PathExists(path, out var isDirectory))
        return;

    if (isDirectory)
    {
        // Do something with your directory
    }
    else
    {
        // Do something with your file
    }
}

如果你想找到目录，包括那些标记为“hidden”和“system”的目录，试试这个(需要。net V4):

FileAttributes fa = File.GetAttributes(path);
if(fa.HasFlag(FileAttributes.Directory))