I raised this question to provide few examples on using C++ methods in C#.
Example based on a small Scenario: I have a structure in C++ and this is the output of a method in C++. I want to use this method in C#.
For this, I have to create a equivalent structure and wrapper method in C#. The structure returned as a pointer from C++. So, we catch that pointer from C# and marshall that pointer to structure.
enum CustomerType //C++ enum Personal = 0 , Corporate = 1 struct Customer //C++ structure _TCHAR CustomerName[ 50 ]; _TCHAR Address[ 250 ]; INT32 CustomerNumber; CustomerType CustomerType; bool IsHandicapped; //C++ method __declspec ( dllexport ) HRESULT ReadCustomer(LPCTSTR cNumber, LPVOID *pCustomer) ..... ..... Customer* objCustomer = (Customer*)CoTaskMemAlloc( sizeof (Customer)); ...... //Fill customer ...... *pCustomer = (LPVOID)(objCustomer); return 0L ; catch (...) The above C++ structures and methods are in native "Customer.dll"
public enum CustomerType // C# enum Personal = 0 , Corporate = 1 [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)] // C# structure public struct Customer [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 50 )] public String CustomerName; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 250 )] public String Address; public int CustomerNumber; public CustomerType CustomerType; [MarshalAs(UnmanagedType.U1)] public bool IsHandicapped; // Equivalent C# wrapper method [DllImport( " Customer.dll" , EntryPoint = " ReadCustomer" , CallingConvention = CallingConvention.Cdecl)] private extern static int GetCustomerDetails([MarshalAs(UnmanagedType.LPTStr)] string cNumber , out IntPtr pCustomer); I will implement a method to use this wrapper to get customer details and marshal the pointer to structure.
public Customer GetCustomerDetails( string cNumber, out bool bStatus) int result = -1; bStatus = false ; IntPtr dataPtr = IntPtr .Zero; Customer objCustomer = new Customer(); result = GetCustomerDetails(cNumber, out dataPtr); if (result == 0 ) objCustomer = (Customer)Marshal.PtrToStructure(dataPtr, typeof (Customer)); Marshal.FreeHGlobal(dataPtr); bStatus = true ; bStatus = false ; catch (Exception ex) Marshal.FreeHGlobal(dataPtr); return objCustomer; Another example of C++ and equivalent C# method.
EntryManager.dll contains the below method:
__declspec ( dllimport ) LONG WINAPI CreateEntry(LPTSTR EntryLocation, LPTSTR EntryName, TCHAR** Belongings, LONG BelongingsSize) //Belongings=Array of items related to Entry
Equivalent C# method for the above is:
[DllImport( " EntryManager.dll" , EntryPoint = " CreateEntry" , CharSet = CharSet.Unicode)] static extern int CreateEntry( [MarshalAs(UnmanagedType.LPWStr)]string EntryLocation, [MarshalAs(UnmanagedType.LPWStr)]string EntryName, [MarshalAsAttribute(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPWStr)] string[] Belongings, int BelongingsSize); // In C++, we can not find the size of array dynamically as we do in C#(like objArray.Length). So, we need to send the size of array.
A different example on notification: When the data changed, notification done using callback mechanism in C++. I want to use the same mechanism in C#. When data changed, that notification should call C# callback method.
//In C++ "EntryManager.dll" typedef void ( __stdcall *CBNotifyFunc)(LPTSTR); DWORD WINAPI ChangeNotify(LPTSTR TargetLocation, int SearchScope, LPTSTR SearchFilter, CBNotify callBackFunction)
// In C# public delegate void CBNotify([MarshalAs(UnmanagedType.LPTStr)]string TargetLocation); [DllImport( " EntryManager.dll" , EntryPoint = " ChangeNotify" , CallingConvention = CallingConvention.Winapi)] public static extern UInt32 GetChangeNotifications([MarshalAs(UnmanagedType.LPWStr)]string TargetLocation, int SearchScope, [MarshalAs(UnmanagedType.LPWStr)]string SearchFilter, [In, MarshalAs(UnmanagedType.FunctionPtr)]CBNotify callBackFunction); public void FunctionCall( string name) MessageBox.Show( " dfd : " + name); // Using the above method GetChangeNotifications uint fsdf = GetChangeNotifications( " EntryLocation1" , 1 , null , FunctionCall); // This registers the Call back method. Whenever there is change, it calls FunctionCalll method.
I have provided the very basic information and code to use C++ methods and structures in C# which is enough to understand this topic.

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