C#调用C++编写的DLL函数各种参数传递问题

1. 不返回值的参数

C++ 原型:

bool    SendNewSms(char *szTel, char *szMessage);

C#引用;

[DllImport( "CdmaCard.dll",EntryPoint="SendNewSms")]

public     static     extern    bool SendNewSms(string phone,string msg);

2. 带返回值(char *)

C++原型:

BOOL GetCardErrorMessage(char *szErrorMessage , int errorCode);

C#引用

[DllImport( "CdmaCard.dll",EntryPoint="GetCardErrorMessage")]

     public     static     extern    int GetCardErrorMessage(StringBuilder msg,int errorCode);

StringBuilder buf = new StringBuilder(1024);//指定的Buf大小必须大于可能的最大长度

       GetCardErrorMessage(buf,1);

3. 带返回值(其他类型)

C++原型:

   BOOL GetSmsSaveStation (int *nSmsStation);

C#引用

   [DllImport( "CdmaCard.dll",EntryPoint="GetSmsSaveStation")]

    public    static    extern   bool GetSmsSaveStation(ref int nStation);

4. 传递结构体指针(C++填充)

C++原型:

struct NET_INFO_STRUCT

{

   DWORD nDurationTime; //持续时间 

   double nReceiveByte; //接收字节

   double nSendByte;   //发送字节

};  

BOOL NetGetConnectDetail(NET_INFO_STRUCT *lpNetInfo);

C#引用

  

public struct NET_INFO_STRUCT

{

   public uint nDurationTime; //持续时间 

   public double nReceiveByte; //接收字节

   public double nSendByte;   //发送字节

}

[DllImport( "CdmaCard.dll",EntryPoint="NetGetConnectDetail")]

         public    static    extern   int NetGetConnectDetail(ref NET_INFO_STRUCT pNetInfo);

        

         NET_INFO_STRUCT netInfo = new NET_INFO_STRUCT();

         NetGetConnectDetail(ref netInfo); 

        

5. 传递结构体数组(C++来填充)

C++原型:

struct UIM_BOOK_STRUCT

{

   int UimIndex;

   char szName[15];

   char szPhone[21];

};

int ReadUimAllBook(UIM_BOOK_STRUCT lpUimBookItem[],int nMaxArraySize);

C#引用

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]//可以指定编码类型

public struct UIM_BOOK_STRUCT

{

   public int UimIndex;

   [MarshalAs(UnmanagedType.ByValTStr, SizeConst= 15)]

   public string szName;

   [MarshalAs(UnmanagedType.ByValTStr, SizeConst= 21)]

   public string szPhone;

};

[DllImport( "CdmaCard.dll",EntryPoint="ReadUimAllBook")]

public    static    extern   int ReadUimAllBook([Out] UIM_BOOK_STRUCT [] lpUimBookItem,int nMaxArraySize);

UIM_BOOK_STRUCT[] p = new UIM_BOOK_STRUCT[20];

int ret = ReadUimAllBook(p,p.Length);

6. 注意问题

类型不一致,会导致调用失败,

(1) long 类型,在C++中是4字节的整数,在C#中是8字节的整数;

(2) 字符串类型的设置不正确;

 

以下是几个简单的window调用

        [System.Security.SuppressUnmanagedCodeSecurity] // We won't use this maliciously

        [DllImport("User32.dll", CharSet=CharSet.Auto)]

        public static extern bool ScreenToClient(IntPtr hWnd, ref System.Drawing.Point rect);

 

        [System.Security.SuppressUnmanagedCodeSecurity] // We won't use this maliciously

        [DllImport("User32.dll", CharSet=CharSet.Auto)]

        public static extern bool GetWindowRect(IntPtr hWnd, out System.Drawing.Rectangle rect);

 

        [System.Security.SuppressUnmanagedCodeSecurity] // We won't use this maliciously

        [DllImport("User32.dll", CharSet=CharSet.Auto)]

        public static extern bool UnregisterClass([MarshalAs(UnmanagedType.LPTStr)] string className, IntPtr instanceHandle);