現在公司要做一個使用C#程式呼叫C++的一個DLL庫，解析檔案的功能。所以在網上找了一些資料。

    一、結構體傳遞

#define JNAAPI extern "C" __declspec(dllexport) // C方式匯出函式

typedef struct    
{  
    int osVersion;  
    int majorVersion;  
    int minorVersion;  
    int buildNum;  
    int platFormId;  
    char szVersion[128];  
}OSINFO;  

// 1. 獲取版本資訊(傳遞結構體指標)  
JNAAPI bool GetVersionPtr( OSINFO *info );  
// 2.獲取版本資訊(傳遞結構體引用)  
JNAAPI bool GetVersionRef(OSINFO &info);  
 

// OSINFO定義
[StructLayout(LayoutKind.Sequential)]
public struct OSINFO
{
	public int osVersion;
	public int majorVersion;
	public int minorVersion;
	public int buildNum;
	public int platFormId;
	[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
	public string szVersion;
}

[DllImport("jnalib.dll", EntryPoint = "GetVersionPtr")]
public static extern bool GetVersionPtr(ref OSINFO info);
public static extern bool GetVersionRef(ref OSINFO info);

IntPtr pv = Marshal.AllocHGlobal(148); //結構體在使用時一定要分配空間(4*sizeof(int)+128)
Marshal.WriteInt32(pv,148); //向記憶體塊裡寫入數值
if (GetVersionPtr(pv)) //直接以非託管記憶體塊地址為引數
{
	Console.WriteLine("--osVersion:{0}", Marshal.ReadInt32(pv, 0));
	Console.WriteLine("--Major:{0}",Marshal.ReadInt32(pv, 4)); //移動4個位元組
	Console.WriteLine("--BuildNum: " + Marshal.ReadInt32(pv, 12));
	Console.WriteLine("--szVersion: "+Marshal.PtrToStringAnsi((IntPtr)(pv.ToInt32()+20)));
}
Marshal.FreeHGlobal(pv); //處理完記得釋放記憶體
 

// 傳遞結構體指標
JNAAPI bool GetVersionArray(OSINFO *info,int nLen);

/**
 * C#介面,對於包含陣列型別,只能傳遞IntPtr
 */ 
[DllImport("jnalib.dll", EntryPoint = "GetVersionArray")]
public static extern bool GetVersionArray(IntPtr p, int nLen);  

// 源目標引數
OSINFO[] infos = new OSINFO[2];
for (int i = 0; i < infos.Length; i++)
{
	infos[i] = new OSINFO();
}

IntPtr[] ptArr = new IntPtr[1];
ptArr[0] = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(OSINFO)) * 2); //分配包含兩個元素的陣列
IntPtr pt = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(OSINFO))); 
Marshal.Copy(ptArr, 0, pt, 1); //拷貝指標陣列
GetVersionArray(pt, 2); //呼叫

//還原成結構體陣列
for (int i = 0; i < 2; i++)  
{
	infos[i]=(OSINFO)Marshal.PtrToStructure((IntPtr)(pt.ToInt32()+i*Marshal.SizeOf(typeof(OSINFO))),typeof(OSINFO));
	Console.WriteLine("OsVersion:{0} szVersion:{1}", infos[i].osVersion, infos[i].szVersion);
}

 1. 輸出引數,結構體作為指標傳出

typedef struct
{
	char name[20];
	int age;
	double scores[30];
}Student;

// Class中包含結構體陣列型別
typedef struct
{
	int number;
	Student students[50];
}Class;

// 傳入複雜結構體測試
JNAAPI int GetClass(Class *pClass,int len);

// 介面定義 
[DllImport("jnalib.dll", EntryPoint = "GetClass")]
public static extern int GetClass(IntPtr pv,int len);

// 結構體定義
// Student
[StructLayout(LayoutKind.Sequential)]
public struct Student
{
	[MarshalAs(UnmanagedType.ByValTStr,SizeConst=20)]
	public string name;
	public int age;
	[MarshalAs(UnmanagedType.ByValArray, SizeConst = 30)]
	public double[] scores;
}

// Class
[StructLayout(LayoutKind.Sequential)]
public struct Class
{
	public int number;
	[MarshalAs(UnmanagedType.ByValArray, SizeConst = 50)] // 指定陣列尺寸 
	public Student[] students; // 結構體陣列定義
}

// 呼叫複雜結構體測試
int size = Marshal.SizeOf(typeof(Class)) * 50;
IntPtr pBuff = Marshal.AllocHGlobal(size); // 直接分配50個元素的空間,比Marshal.copy方便多了
GetClass(pBuff, 50);

Class[] pClass = new Class[50];
for (int i = 0; i < 50; i++)
{
	IntPtr ptr = new IntPtr(pBuff.ToInt64() + Marshal.SizeOf(typeof(Class)) * i);
	pClass[i] = (Class)Marshal.PtrToStructure(ptr, typeof(Class));
}
Marshal.FreeHGlobal(pBuff); // 釋放記憶體

2. 輸入引數, 給複雜結構體賦值後作為輸入引數傳入

   對於比較大的結構體指標,無法直接應用結構體型別,轉化成IntPtr型別, 此時需要將原生型別轉化為指標,並給指標賦值

   呼叫方法: Marshal.StructureToPtr(stu, ptr1, true) 

end...

轉自：http://tcspecial.iteye.com/blog/1675309