Question

I have two forms (Form1 and Form2). On Form1 there is a ‘public int i’ variable, which is set to value 1 in Form1 constructor.
Then I open Form2 from Form1 with this code:

Form2 f2 = new Form2(ref i);
f2.ShowDialog();

The constructor of Form2 looks like this:

public int i;
public Form2(ref int x)
{
    InitializeComponent();
    i = x;
}

Then I set variable i on Form2 to value 2 and close Form2. Now I would expect the variable i on Form1 to have value 2 (because of ‘ref’ keyword by passing parameters), but the value is still 1. What am I doing wrong and why is ref keyword not working in my example?

Thanks

Answer 1

What’s actually happening.

1. You create an object1 with a integer member named “i”
2. You pass a reference to “i” into a new object constructor. The reference to “i” is called “x”.
3. You copy the value of “x” into a variable in the second object, also called “i”.
4. You exit object2’s constructor. The reference to object1.i ends here.
5. You modify object2.i (which is a copy of object1.i, but not a reference, pointer, or link). object1.i is not modified.

There are many ways to accomplish what you want, either with events, or by passing in an object that will be shared between object1 and object2.

Class Form1
{
    Object i = new Object();
    ...
    public void DoSomething()
    {
        Form2 f = new Form2(i);
        f.Show();
    }
}

This would probably be the easiest way to accomplish what you’re going for.