参数异常SHSetKnownFolderPath

Question

我正在尝试使用SHSetKnownFolderPath设置ProgramFiles的“已知文件夹路径”的路径。

以下是我在下面所做的事情但却引发了异常： System.ArgumentException：值不在预期范围内。

using System;
using System.Runtime.InteropServices;


namespace TestApplication {
class Program {

    [Flags]
    public enum KnownFolderFlag : uint {
        None = 0x0,
        CREATE = 0x8000,
        DONT_VERFIY = 0x4000,
        DONT_UNEXPAND = 0x2000,
        NO_ALIAS = 0x1000,
        INIT = 0x800,
        DEFAULT_PATH = 0x400,
        NOT_PARENT_RELATIVE = 0x200,
        SIMPLE_IDLIST = 0x100,
        ALIAS_ONLY = 0x80000000
    }

    [DllImport("shell32.dll")]
    public static extern int SHGetKnownFolderPath(
         [MarshalAs(UnmanagedType.LPStruct)] Guid rfid,
         uint dwFlags,
         IntPtr hToken,
         out IntPtr pszPath  // API uses CoTaskMemAlloc
         );

    [DllImport("shell32.dll")]
    public static extern int SHSetKnownFolderPath(ref Guid guid, uint flags, IntPtr hToken, string newPath);


    public static readonly Guid ProgramFiles = new Guid("905e63b6-c1bf-494e-b29c-65b732d3d21a");
    public static readonly Guid ProgramFilesX64 = new Guid("6D809377-6AF0-444b-8957-A3773F02200E");
    public static readonly Guid ProgramFilesX86 = new Guid("7C5A40EF-A0FB-4BFC-874A-C0F2E0B9FA8E");

    static void Main(string[] args) {

        Guid[] guids = new Guid[] {
            ProgramFiles,
            ProgramFilesX64,
            ProgramFilesX86
        };

        // GET
        foreach (Guid guid in guids) {
            Console.WriteLine(string.Format("{0}; P/Invoke==>{1}", guid.ToString(), pinvokePath(guid)));
            Console.WriteLine("");
        }

        // SET
        Console.WriteLine("SET");
        string thePath = @"C:\ProgramFiles_DCTEST";
        int ret;
        int flags = 0;

        Guid progFiles = ProgramFiles;
        ret = SHSetKnownFolderPath(ref progFiles, (uint)flags, IntPtr.Zero, thePath);

        if (ret != 0) {
            Console.WriteLine(ret);
            Console.WriteLine(Marshal.GetExceptionForHR(ret));
        }
        // SET
        Console.WriteLine("SET");

        Guid progFilesX64 = ProgramFilesX64;
        ret = SHSetKnownFolderPath(ref progFilesX64, (uint)flags, IntPtr.Zero, thePath);

        if (ret != 0) {
            Console.WriteLine(ret);
            Console.WriteLine(Marshal.GetExceptionForHR(ret));
        }

        // SET
        Console.WriteLine("SET");

        Guid progFilesX86 = ProgramFilesX86;
        ret = SHSetKnownFolderPath(ref progFilesX86, (uint)flags, IntPtr.Zero, thePath);

        if (ret != 0) {
            Console.WriteLine(ret);
            Console.WriteLine(Marshal.GetExceptionForHR(ret));
        }

        // GET
        foreach (Guid guid in guids) {
            Console.WriteLine(string.Format("{0}; P/Invoke==>{1}", guid.ToString(), pinvokePath(guid)));
            Console.WriteLine("");
        }

        Console.ReadLine();
    }

    private static string pinvokePath(Guid guid) {
        IntPtr pPath;
        SHGetKnownFolderPath(guid, 0, IntPtr.Zero, out pPath); 

        string path = System.Runtime.InteropServices.Marshal.PtrToStringUni(pPath);
        System.Runtime.InteropServices.Marshal.FreeCoTaskMem(pPath);
        return path;
    }
}
}

欢迎帮助！花了太长时间看这个......