c# 调用 c++的 dll 中关于 char*传入传出参数

c++的dll接口原型为：int CheckSN(const char* InfoList, char* msg);

c#调用转换为：

[DllImport("sncplusInterface.dll", EntryPoint = "CheckSN", ExactSpelling = false, CallingConvention = CallingConvention.Cdecl)]
public static extern int CheckSN(string InfoList, StringBuilder msg);

调用为：

StringBuilder chOutMsg = new StringBuilder(1024);

CheckSN(chData, chOutMsg/*ref chOutMsg*/);

string str = chOutMsg.ToString();

用ref 或 out关键字会crash