Question

var length = new System.IO.FileInfo(path).Length;

这给出了文件的逻辑大小，而不是磁盘上的大小。

我希望在C＃中获取磁盘上的文件大小（最好没有 interop ），就像Windows资源管理器报告的那样。

它应该给出正确的大小，包括：

压缩文件
稀疏文件
碎片文件

Answer 1

使用GetCompressedFileSize，如ho1建议，以及GetDiskFreeSpace，作为PaulStack 建议，它确实使用P / Invoke。我只测试了它的压缩文件，我怀疑它不适用于碎片文件。

    public static long GetFileSizeOnDisk(string file)
    {
        FileInfo info = new FileInfo(file);
        uint dummy, sectorsPerCluster, bytesPerSector;
        int result = GetDiskFreeSpaceW(info.Directory.Root.FullName, out sectorsPerCluster, out bytesPerSector, out dummy, out dummy);
        if (result == 0) throw new Win32Exception();
        uint clusterSize = sectorsPerCluster * bytesPerSector;
        uint hosize;
        uint losize = GetCompressedFileSizeW(file, out hosize);
        long size;
        size = (long)hosize << 32 | losize;
        return ((size + clusterSize - 1) / clusterSize) * clusterSize;
    }

    [DllImport("kernel32.dll")]
    static extern uint GetCompressedFileSizeW([In, MarshalAs(UnmanagedType.LPWStr)] string lpFileName,
       [Out, MarshalAs(UnmanagedType.U4)] out uint lpFileSizeHigh);

    [DllImport("kernel32.dll", SetLastError = true, PreserveSig = true)]
    static extern int GetDiskFreeSpaceW([In, MarshalAs(UnmanagedType.LPWStr)] string lpRootPathName,
       out uint lpSectorsPerCluster, out uint lpBytesPerSector, out uint lpNumberOfFreeClusters,
       out uint lpTotalNumberOfClusters);

Answer 2

上面的代码在Windows Server 2008或2008 R2或基于Windows 7和Windows Vista的系统上无法正常工作，因为群集大小始终为零（即使禁用UAC，GetDiskFreeSpaceW和GetDiskFreeSpace也会返回-1。）以下是修改后的代码。

<强> C＃

public static long GetFileSizeOnDisk(string file)
{
    FileInfo info = new FileInfo(file);
    uint clusterSize;
    using(var searcher = new ManagementObjectSearcher("select BlockSize,NumberOfBlocks from Win32_Volume WHERE DriveLetter = '" + info.Directory.Root.FullName.TrimEnd('\\') + "'") {
        clusterSize = (uint)(((ManagementObject)(searcher.Get().First()))["BlockSize"]);
    }
    uint hosize;
    uint losize = GetCompressedFileSizeW(file, out hosize);
    long size;
    size = (long)hosize << 32 | losize;
    return ((size + clusterSize - 1) / clusterSize) * clusterSize;
}

[DllImport("kernel32.dll")]
static extern uint GetCompressedFileSizeW(
   [In, MarshalAs(UnmanagedType.LPWStr)] string lpFileName,
   [Out, MarshalAs(UnmanagedType.U4)] out uint lpFileSizeHigh);

<强> VB.NET

  Private Function GetFileSizeOnDisk(file As String) As Decimal
        Dim info As New FileInfo(file)
        Dim blockSize As UInt64 = 0
        Dim clusterSize As UInteger
        Dim searcher As New ManagementObjectSearcher( _
          "select BlockSize,NumberOfBlocks from Win32_Volume WHERE DriveLetter = '" + _
          info.Directory.Root.FullName.TrimEnd("\") + _
          "'")

        For Each vi As ManagementObject In searcher.[Get]()
            blockSize = vi("BlockSize")
            Exit For
        Next
        searcher.Dispose()
        clusterSize = blockSize
        Dim hosize As UInteger
        Dim losize As UInteger = GetCompressedFileSizeW(file, hosize)
        Dim size As Long
        size = CLng(hosize) << 32 Or losize
        Dim bytes As Decimal = ((size + clusterSize - 1) / clusterSize) * clusterSize

        Return CDec(bytes) / 1024
    End Function

    <DllImport("kernel32.dll")> _
    Private Shared Function GetCompressedFileSizeW( _
        <[In](), MarshalAs(UnmanagedType.LPWStr)> lpFileName As String, _
        <Out(), MarshalAs(UnmanagedType.U4)> lpFileSizeHigh As UInteger) _
        As UInteger
    End Function

Answer 3

根据MSDN社交论坛：

磁盘上的大小应该是存储文件的群集大小的总和：
  long sizeondisk = clustersize * ((filelength + clustersize - 1) / clustersize);
  您需要进入P/Invoke以查找群集大小; GetDiskFreeSpace()返回它。

请参阅 How to get the size on disk of a file in C# 。

但请注意，这在NTFS开启压缩的情况下无效。

Answer 4

我认为会是这样的：

double ifileLength = (finfo.Length / 1048576); //return file size in MB ....

我还在为此做一些测试，以获得确认。

获取磁盘上的文件大小

4 个答案: