Interoperability with Other .NET Languages (C++/CLI)

The topics in this section show how to create assemblies in Visual C++ that consume from or provide functionality to assemblies written in C# or Visual Basic.

Consume a C# Indexer

Visual C++ does not contain indexers; it has indexed properties. To consume a C# indexer, access the indexer as if it were an indexed property.

For more information about indexers, see:

• Indexers

Example

The following C# program defines an indexer.

// consume_cs_indexers.cs
// compile with: /target:library
using System;
public class IndexerClass {
   private int [] myArray = new int[100];
   public int this [int index] {   // Indexer declaration
      get {
         // Check the index limits.
         if (index < 0 || index >= 100)
            return 0;
         else
            return myArray[index];
      }
      set {
         if (!(index < 0 || index >= 100))
            myArray[index] = value;
      }
   }
}
/*
// code to consume the indexer
public class MainClass {
   public static void Main() {
      IndexerClass b = new IndexerClass();

      // Call indexer to initialize elements 3 and 5
      b[3] = 256;
      b[5] = 1024;
      for (int i = 0 ; i <= 10 ; i++)
         Console.WriteLine("Element #{0} = {1}", i, b[i]);
   }
}
*/

This C++/CLI program consumes the indexer.

// consume_cs_indexers_2.cpp
// compile with: /clr
#using "consume_cs_indexers.dll"
using namespace System;

int main() {
   IndexerClass ^ ic = gcnew IndexerClass;
   ic->default[0] = 21;
   for (int i = 0 ; i <= 10 ; i++)
      Console::WriteLine("Element #{0} = {1}", i, ic->default[i]);
}

The example produces this output:

Element #0 = 21
Element #1 = 0
Element #2 = 0
Element #3 = 0
Element #4 = 0
Element #5 = 0
Element #6 = 0
Element #7 = 0
Element #8 = 0
Element #9 = 0
Element #10 = 0

Implement is and as C# Keywords

This topic shows how to implement the functionality of the is and as C# keywords in Visual C++.

Example

// CS_is_as.cpp
// compile with: /clr
using namespace System;

interface class I {
public:
   void F();
};

ref struct C : public I {
   virtual void F( void ) { }
};

template < class T, class U >
Boolean isinst(U u) {
   return dynamic_cast< T >(u) != nullptr;
}

int main() {
   C ^ c = gcnew C();
   I ^ i = safe_cast< I ^ >(c);   // is (maps to castclass in IL)
   I ^ ii = dynamic_cast< I ^ >(c);   // as (maps to isinst in IL)

   // simulate 'as':
   Object ^ o = "f";
   if ( isinst< String ^ >(o) )
      Console::WriteLine("o is a string");
}

o is a string

Implement the lock C# Keyword

This topic shows how to implement the C# lock keyword in Visual C++.

You can also use the lock class in the C++ Support Library. See Synchronization (lock Class) for more information.

Example

// CS_lock_in_CPP.cpp
// compile with: /clr
using namespace System::Threading;
ref class Lock {
   Object^ m_pObject;
public:
   Lock( Object ^ pObject ) : m_pObject( pObject ) {
      Monitor::Enter( m_pObject );
   }
   ~Lock() {
      Monitor::Exit( m_pObject );
   }
};

ref struct LockHelper {
   void DoSomething();
};

void LockHelper::DoSomething() {
   // Note: Reference type with stack allocation semantics to provide
   // deterministic finalization

   Lock lock( this );
   // LockHelper instance is locked
}

int main()
{
   LockHelper lockHelper;
   lockHelper.DoSomething();
   return 0;
}

See also

.NET Programming with C++/CLI (Visual C++)