求救，C# 调用C编写的dll问题

Question

C原型：
typedef enum _SUPPORT_LAYER
{
HDLC = 0x01,
TCPIP,
UDPIP
}SUPPORT_LAYER;

typedef union _ADDR
{
    struct
    {
        unsigned int ServerLowerAddr : 14;  //服务器低地址
        unsigned int ServerUpperAddr : 14;  //服务器高地址
        unsigned int res : 4;
        unsigned char ClientAddr;
        unsigned char ServerAddrLen;
    }HDLC_ADDR1;    struct
    {
        unsigned int ServerAddr : 28;
        unsigned int res : 4;
        unsigned char ClientAddr;
        unsigned char ServerAddrLen;
    }HDLC_ADDR2;    struct
    {
        unsigned int Client_TCP_Port;
        unsigned int Server_TCP_Port;
        unsigned char Client_IP_Addr[4];
        unsigned char Server_IP_Addr[4];
    }TCPIP_ADDR;    struct
    {
        unsigned int Client_wPort;
        unsigned int Server_wPort;
        unsigned int Client_UDP_Port;
        unsigned int Server_UDP_Port;
        unsigned char Client_IP_Addr[4];
        unsigned char Server_IP_Addr[4];
    }UDPIP_ADDR;  
}ADDR;  int ProcessServicePrimitive(unsigned char **OUTData, unsigned int &OUTDataLen,SUPPORT_LAYER SupportLayerType, ADDR Addr,const unsigned char *Xml, unsigned int XmlLen);
请问如何用C#调用ProcessServicePrimitive参数？C#Cstruct

Answer 1

 public enum SUPPORT_LAYER
        {
            HDLC = 0x01,
            TCPIP,
            UDPIP
        }
      
        [StructLayout(LayoutKind.Sequential)]
        public struct HDLC_ADDR1
        {
           public uint ServerLowerAddr;
           public uint ServerUpperAddr;
           public uint res;
           public char ClientAddr;
           public char ServerAddrLen;
        };
        [StructLayout(LayoutKind.Sequential)]
        public struct HDLC_ADDR2
        {
            public uint ServerAddr;
            public uint res;
            public char ClientAddr;
            public char ServerAddrLen;
        }
        [StructLayout(LayoutKind.Sequential)]
        public struct TCPIP_ADDR
        {
            public uint Client_TCP_Port;
            public uint Server_TCP_Port;
            public char [] Client_IP_Addr;
            public char [] Server_IP_Addr;
        }
        [StructLayout(LayoutKind.Sequential)]
        public struct UDPIP_ADDR
        {
            public uint Client_wPort;
            public uint Server_wPort;
            public uint Client_UDP_Port;
            public uint Server_UDP_Port;
            public char [] Client_IP_Addr;
            public char [] Server_IP_Addr;
        }
        [StructLayout(LayoutKind.Explicit,Size=500)]        public struct ADDR
        {            [FieldOffset(0)]
            public HDLC_ADDR1 a;            [FieldOffset(50)]
            public HDLC_ADDR2 b;            [FieldOffset(180)]
            public TCPIP_ADDR c;            [FieldOffset(300)]
            public UDPIP_ADDR d;
        }
 [DllImport("pro_C62056.dll")]
        public static extern int ProcessServicePrimitive(
 ref string str, ref UInt32 len, SUPPORT_LAYER SupportLayerType, ADDR Addr,
 string  strxml, int len1);
我这样调用老是提示外部组件异常

Answer 2

Union应该是共享地址的，大小为最大的结构体所占的大小
        [StructLayout(LayoutKind.Explicit,Size=24)]
        public struct ADDR
        {            [FieldOffset(0)]
            public HDLC_ADDR1 a;            [FieldOffset(0)]
            public HDLC_ADDR2 b;            [FieldOffset(0)]
            public TCPIP_ADDR c;            [FieldOffset(0)]
            public UDPIP_ADDR d;
        }