How can I determine if a remote drive has enough s

问题:

How can I determine if a remote drive has enough space for me to upload a given file using C# in .Net?

回答1:

There are two possible solutions.

1. Call the Win32 function GetDiskFreeSpaceEx. Here is a sample program:

   internal static class Win32
   {
       [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
       internal static extern bool GetDiskFreeSpaceEx(string drive, out long freeBytesForUser, out long totalBytes, out long freeBytes);
   
   }
   
   class Program
   {
       static void Main(string[] args)
       {
           long freeBytesForUser;
           long totalBytes;
           long freeBytes;
   
           if (Win32.GetDiskFreeSpaceEx(@"\\prime\cargohold", out freeBytesForUser, out totalBytes, out freeBytes)) {
               Console.WriteLine(freeBytesForUser);
               Console.WriteLine(totalBytes);
               Console.WriteLine(freeBytes);
           }
       }
   }
   

2. Use the system management interface. There is another answer in this post which describes this. This method is really designed for use in scripting languages such as PowerShell. It performs a lot of fluff just to get the right object. Ultimately, I suspect, this method boils down to calling GetDiskFreeSpaceEx.

Anybody doing any serious Windows development in C# will probably end up calling many Win32 functions. The .NET framework just doesn't cover 100% of the Win32 API. Any large program will quickly uncover gaps in the .NET libraries that are only available through the Win32 API. I would get hold of one of the Win32 wrappers for .NET and include this in your project. This will give you instant access to just about every Win32 API.

回答2:

Use WMI

using System.Management;

// Get all the network drives (drivetype=4)
SelectQuery query = new SelectQuery("select Name, VolumeName, FreeSpace from win32_logicaldisk where drivetype=4");
ManagementObjectSearcher searcher = new ManagementObjectSearcher(query);
foreach (ManagementObject drive in searcher.Get())
{
    string Name = (string)drive["Name"];
    string VolumeName = (string)drive["VolumeName"];
    UInt64 freeSpace = (UInt64)drive["FreeSpace"];
}

based on (stolen from) http://www.dreamincode.net/code/snippet1576.htm

回答3:

Are you talking about mapping a network share to a logical drive on you computer?

If so you can use DriveInfo.

    DriveInfo info = new DriveInfo("X:");

    info.AvailableFreeSpace;

DriveInfo only works with logical drives so if you are just using the full share (UNC) name I don't think the above code will work.

回答4:

I'm not sure if GetDiskFreeSpaceEx works on UNC shares, but if it does use that, otherwise here is how to mount a UNC share to a logal drive:

EDIT GetDiskFreeSpaceEx does work on UNC shares, use that...however, this code was too much effort to just delete, and is handy if you ever want to mount a UNC share as a local drive in your code.

public class DriveWrapper
{                    
    [StructLayout(LayoutKind.Sequential)]
    public struct NETRESOURCEA
    {
        public int dwScope;
        public int dwType;
        public int dwDisplayType;
        public int dwUsage;
        [MarshalAs(UnmanagedType.LPStr)]
        public string lpLocalName;
        [MarshalAs(UnmanagedType.LPStr)]
        public string lpRemoteName;
        [MarshalAs(UnmanagedType.LPStr)]
        public string lpComment;
        [MarshalAs(UnmanagedType.LPStr)]
        public string lpProvider;
        public override String ToString()
        {
            String str = "LocalName: " + lpLocalName + " RemoteName: " + lpRemoteName
                  + " Comment: " + lpComment + " lpProvider: " + lpProvider;
            return (str);
        }
    }

    [DllImport("mpr.dll")]
    public static extern int WNetAddConnection2A(
          [MarshalAs(UnmanagedType.LPArray)] NETRESOURCEA[] lpNetResource,
          [MarshalAs(UnmanagedType.LPStr)] string lpPassword,
          [MarshalAs(UnmanagedType.LPStr)] string UserName,
          int dwFlags);       
    [DllImport("mpr.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto)]
    private static extern int WNetCancelConnection2A(
          [MarshalAs(UnmanagedType.LPStr)]
        string lpName,
          int dwFlags,
          int fForce
          );

    public int GetDriveSpace(string shareName, string userName, string password)
    {
        NETRESOURCEA[] n = new NETRESOURCEA[1];
        n[0] = new NETRESOURCEA();

        n[0].dwScope = 0;
        n[0].dwType = 0;
        n[0].dwDisplayType = 0;
        n[0].dwUsage = 0;

        n[0].dwType = 1;

        n[0].lpLocalName = "x:";
        n[0].lpRemoteName = shareName;
        n[0].lpProvider = null;

        int res = WNetAddConnection2A(n, userName, password, 1);

        DriveInfo info = new DriveInfo("x:");
        int space = info.AvailableFreeSpace;

        int err = 0;
        err = WNetCancelConnection2A("x:", 0, 1);

        return space;
    }
}