How to: Implement is and as C# Keywords in C++

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

For more information, see is (C# Reference) and as (C# Programmer's Reference).


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

interface class I {
   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

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