C # mixed programming with C ++

For historical reasonsCodeIt is not entirely written using. net. At this time, mixed programming with the previous C ++ code is very important. I recently encountered such a problem and briefly described the method as follows.

Call simple C ++ Functions

The general idea of calling C ++ functions in C # code is as follows: First, write the C ++ functions as libraries in the DLL format, then, import the functions in the DLL in C # For calling. The specific code is similar to this:
C ++ code:

  1   Int  Staticelementnumber  =     10  ;
  2     Extern     "  C  "  Afx_api_export  Int  Getarrayelementnumber ()
  3   {
  4     Return  Staticelementnumber;
  5   } 

C # code:
(Import the function, which is written in the class where the function is called)

  1   [Dllimport (  "  Mfcdll. dll  "  )]
  2      Public     Static     Extern    Int  Getarrayelementnumber ();
  3      Int  Elementnumber  =  Getarrayelementnumber (); 

The details in S, such as int and char data types occupying different spaces in C ++ and C #, are automatically processed by CLR. (Mainly through automatic processing of Marshal class)

Such a call also supports debugging. Open the properties of the C # project, and select enable unmanaged code debugging on the debug tab to enable C ++ code debugging. In this way, when calling this function, you can continue to follow up the internal debugging of the function by F11.

Passing a GDI object

Some Complex windows objects can be transferred through handles. For example, the following code converts a GDI + bitmap object into a GDI handle for transmission.
C ++ Code (the Declaration and reference of GDI + are omitted ):

  1   Extern     "  C  "  Afx_api_export hbitmap getabitmap (wchar  *  Strfilename)
  2   {
  3   Gdiplus: gdiplusstartupinput;
 4   Ulong_ptr gdiplustoken;
  5   Gdiplusstartup (  &  Gdiplustoken,  &  Gdiplusstartupinput, null );
  6   Bitmap  *  Bitmap  =  Bitmap: fromfile (strfilename );
  7  Hbitmap hbitmaptoreturn;
  8   Bitmap  ->  Gethbitmap (null,  &  Hbitmaptoreturn );
  9   Gdiplusshutdown (gdiplustoken );
  10   
  11     Return  Hbitmaptoreturn;
 12   } 

C # code (the user interface uses WPF, with the relevant declarations and references omitted ):

  1   [Dllimport (  "  Mfcdll. dll  "  )]
  2      Public     Static    Extern  Intptr getabitmap ([financialas (unmanagedtype. lpwstr)]  String  Strfilename );
  3   
  4      Private     Void  Menuitemfileopenonclicked (  Object  Sender, routedeventargs E)
  5   {
 6   Openfiledialog Dialog  =     New  Openfiledialog ();
  7   Dialog. Title  =     "  Load an image...  "  ;
  8   Dialog. multiselect  =    False  ;
  9     If  (Dialog. showdialog ()  =     True  )
  10   {
  11   Maingrid. Children. Clear ();
  12   
 13   Intptr hbitmap  =  Getabitmap (dialog. filename );
  14   Bitmap bitmap  =  Bitmap. fromhbitmap (hbitmap );
  15   System. Windows. Controls. Image  =     New  Windows. Controls. Image ();
  16  Image. Source  =  Windows. InterOP. imaging. createbitmapsourcefromhbitmap (hbitmap, Ro, int32rect. empty,
  17   Windows. Media. imaging. bitmapsizeoptions. fromemptyoptions ());
  18   Image. Stretch  =  System. Windows. Media. Stretch. Fill;
  19   Deleteobject (hbitmap );
  20   Maingrid. Children. Add (image );
 21   }
  22   } 

 

 

 

Passing Arrays

It is easy to pass a fixed-length array, which is not described here. The following code transfers a variable-length array:
C ++ code:

   1   Int  Staticelementnumber  =     10  ;
 2     Extern     "  C  "  Afx_api_export  Bool  Getarray (  Int  Elementnumber,  Double     *  Baseaddress)
  3  {
  4     If  (Elementnumber  <  Staticelementnumber)
  5   {
  6     Return     False  ;
  7   }
 8   
  9     For  (  Int  I  =     0  ; I  <  Staticelementnumber;  ++  I)
  10   {
 11   Baseaddress [I]  =     1     /  ((  Double  ) I  +     1  );
  12   }
  13   
 14     Return     True  ;
  15   }
  16   
  17     Extern     "  C  "  Afx_api_export Int  Getarrayelementnumber ()
  18   {
  19     Return  Staticelementnumber;
  20   } 

 

 

C # code:

   1   [Dllimport (  " Mfcdll. dll  "  )]
  2     Public     Static     Extern     Bool  Getarray (  Int  Elementnumber, [financialas (unmanagedtype. lparray, sizeparamindex  =    0  )]  Double  [] Baseaddress );
  3   
  4     Private     Void  Menuitemfilegetarrayonclicked (  Object  Sender, routedeventargs E)
  5   {
  6    //  Get array data.  
  7       Int  Elementnumber  =  Getarrayelementnumber ();
  8     Double  [] Doublearray  =    New     Double  [Elementnumber];
  9   Getarray (elementnumber, doublearray );
  10   
  11     //  Show the data.  
  12     Maingrid. Children. Clear ();
 13   ListBox  =     New  ListBox ();
  14     Foreach  (  Double  Number  In  Doublearray)
  15   {
  16  ListBox. Items. Add (number );
  17   }
  18   Maingrid. Children. Add (ListBox );
  19   }
  20    

With these three functions, it is relatively simple to reuse C ++ code on the C # platform.