Question

This question probably has already been answered, I may be type the wrong question in google, but I want to run the function time_refresh that is on form1 and works well from form2. this what I got so far:

Form1

public void time_refresh()
    {
        run_stop.Text = Properties.Settings.Default.s_update + " " + Properties.Settings.Default.s_update_int;
        run_stop.ForeColor = Color.Green;
    }

Form2

private Main_form_1 form1 = null;

and

form1.time_refresh();

But it get an error

Object reference not set to an instance of an object.
Kind of new to c# so any help would be excellent.

Answer 1

The proper way to address this issue is through events. Form2 shouldn’t be accessing Form1 directly, it should simply be informing Form1 that it needs to update itself through an event.

On Form2 create some event like:

public Action event Refresh; //TODO rename as appropriate

Then, on Form2 you can fire that event whenever you want Form1 to know that it needs to refresh itself:

public void OnRefresh()  //call this method to fire the event
{
    if(Refresh != null)
        Refresh();
}

Then on Form1 you can attach an event handler:

Form2 other = new Form2();
other.Refresh += () => time_refresh();
other.Show();