Get file size without using System.IO.FileInfo?

Question

Is it possible to get the size of a file in C# without using System.IO.FileInfo at all?

I know that you can get other things like Name and Extension by using Path.GetFileName(yourFilePath) and Path.GetExtension(yourFilePath) respectively, but apparently not file size? Is there another way I can get file size without using System.IO.FileInfo?

The only reason for this is that, if I'm correct, FileInfo grabs more info than I really need, therefore it takes longer to gather all those FileInfo's if the only thing I need is the size of the file. Is there a faster way?

Answer 1

I performed a benchmark using these two methods:

    public static uint GetFileSizeA(string filename)
    {
        WIN32_FIND_DATA findData;
        FindFirstFile(filename, out findData);
        return findData.nFileSizeLow;
    }

    public static uint GetFileSizeB(string filename)
    {
        IntPtr handle = CreateFile(
            filename,
            FileAccess.Read,
            FileShare.Read,
            IntPtr.Zero,
            FileMode.Open,
            FileAttributes.ReadOnly,
            IntPtr.Zero);
        long fileSize;
        GetFileSizeEx(handle, out fileSize);
        CloseHandle(handle);
        return (uint) fileSize;
    }

Running against a bit over 2300 files, GetFileSizeA took 62-63ms to run. GetFileSizeB took over 18 seconds.

Unless someone sees something I'm doing wrong, I think the answer is clear as to which method is faster.

Is there a way I can refrain from actually opening the file?

Update

Changing FileAttributes.ReadOnly to FileAttributes.Normal reduced the timing so that the two methods were identical in performance.

Furthermore, if you skip the CloseHandle() call, the GetFileSizeEx method becomes about 20-30% faster, though I don't know that I'd recommend that.