Execute an objects method without making a new instance - object

Question

How can I execute Print from within TestObject?
class Program
{
private int Value;
static void Main()
{
TestObject test = new TestObject();
Program p1 = new Program();
Program p2 = new Program();
p1.Value = 1;
p2.Value = 2;
p1.Print();
p2.Print();
}
private void Print()
{
Console.Write(Value.ToString());
Console.ReadKey();
}
}
class TestObject
{
// How to execute p1.Print here?
}

Answer 1

There are multiple ways to do this:
Pass Program directly to TestObject
Pros:
Simple change
Cons:
You will have to make Print public
You will expose other things in Program
You're coupling TestObject to Program directly
Here's sample code:
class Program
{
static void Main()
{
TestObject test = new TestObject(this);
}
public void Print()
{
Console.Write(Value.ToString());
Console.ReadKey();
}
}
class TestObject
{
public TestObject(Program p)
{
p.Print();
}
}
Pass a delegate to TestObject
Pros:
Simple change
Doesn't have to make Print public
Only exposes 1 method to TestObject
Cons:
The coupling is TestObject wants to do something, not TestObject wants access to something that does something
Here's sample code:
class Program
{
static void Main()
{
TestObject test = new TestObject(() => Print());
}
private void Print()
{
Console.Write(Value.ToString());
Console.ReadKey();
}
}
class TestObject
{
public TestObject(Action print)
{
print();
}
}
Implement an interface in Program and pass it to TestObject
Pros:
Only exposes what the interface exposes
Easier to implement other places (better to say "need this interface" than "needs a delegate", clearer contract specification)
No coupling to a specific type, coupling is to any object that meets certain criteria - implements an interface
Cons:
None relevant (in my opinion)
Here's sample code:
interface IPrintable
{
void Print();
}
class Program : IPrintable
{
static void Main()
{
TestObject test = new TestObject(this);
}
public void Print()
{
Console.Write(Value.ToString());
Console.ReadKey();
}
}
class TestObject
{
public TestObject(IPrintable p)
{
p.Print();
}
}
Conclusion: My advice would be to pick the interface way. Clearer design, easier to extend without having multiple delegates being passed around.