Copy a value type variable

Simply make the copy. Because the variable is a value type, you will have two copies of the same value. For example:

int i = 42; 
int copyi = i;

Copy a reference type variable

Simply make the copy. Because the variable is a reference type, you will have two references to the same object. For example:

Circle c = new Circle(42);  
Circle refc = c;

Pass an argument to a ref parameter

Prefix the argument with the ref keyword. This makes the parameter an alias for the actual argument rather than a copy of the argument. For example:

static void Main()  
{  
    int arg = 42;  
    DoWork(ref arg);  
    Console.WriteLine(arg);  
}

Pass an argument to an out parameter

Prefix the argument with the out keyword. This makes the parameter an alias for the actual argument rather than a copy of the argument. For example:

static void Main()  
{  
    int arg = 42;  
    DoWork(out arg);  
    Console.WriteLine(arg);  
}

Box a value

Initialize or assign a variable of type object to the value. For example:

object o = 42;

Unbox a value

Cast the object reference that refers to the boxed value to the type of the value. For example:

int i = (int)o;