C#中调用C++ DLL(P/Invoke)

　　DLL 需传出char *类型
[DllImport(“MyDLL.dll")]
// 传出值
public static extern int mySum (StringBuilder abuf， StringBuilder bbuf );
　　//DLL中申明
extern “C” __declspec(dllexport)  int WINAPI mySum(char * astr，char * bstr)
{
//传出char *　改变astr　bstr -->abuf， bbuf可以被改变
return a+b;
}
　　DLL 回调函数
　　BOOL EnumWindows(WNDENUMPROC lpEnumFunc， LPARAM lParam)
using System;
using System.Runtime.InteropServices;
public delegate bool CallBack(int hwnd， int lParam); //定义委托函数类型
public class EnumReportApp
{
[DllImport("user32")]
public static extern int EnumWindows(CallBack x， int y);
public static void Main() {
CallBack myCallBack = new CallBack(EnumReportApp.Report); EnumWindows(myCallBack， 0);
}
public static bool Report(int hwnd， int lParam)
{
Console.Write("Window handle is ");
Console.WriteLine(hwnd); return true;
}
}
　　DLL  传递结构   （见代码）
　　BOOL PtInRect(const RECT *lprc， POINT pt);
using System.Runtime.InteropServices;
[StructLayout(LayoutKind.Sequential)]
public struct Point {
public int x;
public int y;
}
[StructLayout(LayoutKind.Explicit)]
public struct Rect
{
[FieldOffset(0)] public int left;
[FieldOffset(4)] public int top;
[FieldOffset(8)] public int right;
[FieldOffset(12)] public int bottom;
}
Class XXXX {
[DllImport("User32.dll")]
public static extern bool PtInRect(ref  Rect r， Point p);
}