调用vc的dll 返回 char * 怎样接收？ 小弟我快疯了！不揭帖不睡觉

调用vc的dll 返回 char * 怎样接收？？？ 我快疯了！！！不揭帖不睡觉
VC 的头文件这样声明的
_PORT_ char *OCode(unsigned long fIDMode,bool fReference,char *lpFileName);

我这样调用
  [DllImport(@"OCode.dll")]
  public static extern StringBuilder OCode(long fIDMode, bool fReference,StringBuilder s);


  StringBuilder a1 = new StringBuilder("132132");

  StringBuilder b1 = new StringBuilder(); 

  b1 = OCode(2, false, ddd);
  不管怎样都得不到返回值，高手给我看看，调用是否正确？？？



[解决办法]
vc:unsigned long -->c#:uint
[解决办法]
[DllImport(@"OCode.dll")] 
public static extern StringBuilder OCode(uint fIDMode, bool fReference,StringBuilder s); 


试一试
[解决办法]
[DllImport(@"OCode.dll")] 
 public static extern StringBuilder OCode(uint fIDMode, bool fReference,StringBuilder s); 

[解决办法]
stringbuilder是引用类型 -- 》 char*

string类型不能作为指针用

实在不行直接设置一个不安全代码段 直接对着引用调用
[解决办法]
[DllImport(@"OCode.dll")] 
public static extern StringBuilder OCode(uint fIDMode, bool fReference,string s);
[解决办法]
[DllImport(@"OCode.dll", EntryPoint = "JL_GetOneReport", CallingConvention = CallingConvention.StdCall)]
public static extern string OCode(uint fIDMode, bool fReference, string s); 




[DllImport(@"OCode.dll", EntryPoint = "JL_GetOneReport", CallingConvention = CallingConvention.StdCall)]
public static extern string OCode(uint fIDMode, bool fReference, ref string s);