[.net] .net managed C++ using pointers/references

Hej How do i make a reference to another object. For example i want a function that take a string as input and adds texts to the string, which then can be used outside the function. (I want pointers or regerence) String ^text = gcnew String("asd"); //"asd" f00(text); //"asdsnake" void f00(String ^str) { str+= "snake"; }