C#调用C++编写的DLL函数各种参数传递问题
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);
调用：
int[] mydata = new int[1024];
GetSmsSaveStation(ref mydata[0]);
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);