C#调用cdll指针参数处理

1、API声明（包括**参数)

int GetTheLastErrorA(char **pcError)；
int GetTheLastErrorW(wchar_t **pwError)；

2、C#代码

using System.Runtime.InteropServices;

[DllImport("StringAW.dll", CallingConvention = CallingConvention.Winapi, 
CharSet = CharSet.Ansi, EntryPoint = "GetTheLastErrorA")]
extern static int GetTheLastErrorA(ref IntPtr a);

[DllImport("StringAW.dll", CallingConvention = CallingConvention.Winapi, 
CharSet = CharSet.Auto, EntryPoint = "GetTheLastErrorW")]
extern static int GetTheLastErrorW(ref IntPtr w);

IntPtr a = IntPtr.Zero;
GetTheLastErrorA(ref a);
String sa = Marshal.PtrToStringAnsi(a);
MessageBox.Show(sa);

IntPtr w = IntPtr.Zero;
GetTheLastErrorW(ref w);
String sw = Marshal.PtrToStringUni(w);
MessageBox.Show(sw);