c#调用C++ dll struct 匹配

请问C++的结构体为：
typedef struct {
unsigned char a;
unsigned char b;
double c;
unsigned char d
double e;
unsigned char f;
} T1;
C#里的结构体应该怎样定义来匹配？

http://blog.csdn.net/sundk911/article/details/7766954