C#调用C++dll传参问题

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转自：http://blog.csdn.net/wen158809179/article/details/5704701

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);

关于c#调用C++数据类型的对应关系可参考此篇博文：http://blog.csdn.net/xqf222/article/details/5877795

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