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Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here.

How to: Pass CLR Types by Reference with Tracking References

The following sample shows how to pass CLR types by reference with tracking references.

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

ref struct City {
private:
   Int16 zip_;

public:
   City (int zip) : zip_(zip) {};
   property Int16 zip {
      Int16 get(void) {
         return zip_;
      }   // get
   }   // property
};

void passByRef (City ^% myCity) {
   // cast needed so this pointer in City struct is "const City"
   if (myCity->zip == 20100)
      Console::WriteLine("zip == 20100");
   else
      Console::WriteLine("zip != 20100");
}

ref class G {
public:
   int i;
};

void Test(int % i) {
   i++;
}

int main() {
   G ^ g1 = gcnew G;
   G ^% g2 = g1;
   g1 -> i = 12;

   Test(g2->i);   // g2->i will be changed in Test2()

   City ^ Milano = gcnew City(20100);
   passByRef(Milano);
}

Output

zip == 20100

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