如何处理失败的DllImport？

Question

我正在尝试编写一个C#托管类来包装SHGetKnownFolderPath,到目前为止它可以在Vista上运行,但由于没有按预期在shell32.dll中找到正确的函数而在XP上崩溃.

我想让它设置好所以如果使用XP,我可以使用System.Environment.GetFolderPath回避(通常是hacky)解决方案.(或者,更好的是,如果它在shell32中找不到功能.)

除了条件编译之外,还有什么方法可以做到这一点吗？

我目前的代码如下:

public abstract class KnownFolders
    {
        [DllImport("shell32.dll")]
        private static extern int SHGetKnownFolderPath([MarshalAs(UnmanagedType.LPStruct)] Guid rfid, uint dwFlags, IntPtr hToken, out IntPtr pszPath);

        // Trim properties to get various Guids.

        public static string GetKnownFolderPath(Guid guid)
        {
            IntPtr pPath;
            int result = SHGetKnownFolderPath(guid, 0, IntPtr.Zero, out pPath);
            if (result == 0)
            {
                string s = Marshal.PtrToStringUni(pPath);
                Marshal.FreeCoTaskMem(pPath);
                return s;
            }
            else
                throw new System.ComponentModel.Win32Exception(result);
        }
    }

Answer 1

在try-catch块中包含对SHGetKnownFolderPath的调用.捕获System.EntryPointNotFoundException,然后尝试替代解决方案:

public static string GetKnownFolderPath(Guid guid)
{
  try
  {
    IntPtr pPath;
    int result = SHGetKnownFolderPath(guid, 0, IntPtr.Zero, out pPath);
    if (result == 0)
    {
        string s = Marshal.PtrToStringUni(pPath);
        Marshal.FreeCoTaskMem(pPath);
        return s;
    }
    else
        throw new System.ComponentModel.Win32Exception(result);
  }
  catch(EntryPointNotFoundException ex)
  {
    DoAlternativeSolution();
  }
}