Public method not triggered cross forms

Question

When I try to call a method on form1 from form2, as per the following code, nothing happens:

form2:

Form1 form1 = new Form1();
form1.AddToListView();

form1:

public void AddToListView()
{
    AddList();
    listView1.Items.Add("Test", "Test", 0);
    label1.Text = "Test";
}

What am I doing wrong?

`form1.Show();` to show the form, because you're creating a new `Form1` — Alessandro D'Andria, Sep 08 '13 at 17:16
I want to do the same as VB: This is what i will do if i was deveoping in VB: Form2: Form1.Label1 = "LOL" — Mariogrip, Sep 08 '13 at 17:24
possible duplicate of [There is a Default instance of form in VB.Net but not in C#, WHY?](http://stackoverflow.com/questions/4698538/there-is-a-default-instance-of-form-in-vb-net-but-not-in-c-why) — Hans Passant, Sep 08 '13 at 17:28
Try with this `var form1 = (this.Owner as Form1); if (form1 != null) { /*put here your code*/ }`, i'am assuming you open form2 from form1, but really it's hard to answer. — Alessandro D'Andria, Sep 08 '13 at 17:30

score 5 · Answer 1 · answered Sep 08 '13 at 17:18

5

With Form1 form1 = new Form1(); you are creating a new instance of the form, not referencing your main form1 which I'm assuming is your problem.

You either need to pass the reference of form1 to form2's constructor, or discard your current form1 and change form2 to:

Form1 form1 = new Form1();
form1.Show();
form1.AddToListView();

answered Sep 08 '13 at 17:18

Alfie

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But the form is already open... – Mariogrip Sep 08 '13 at 17:21
3

An **instance** of your form might be open, but it's not the one that you are affecting with your call to `AddToListView`. You can make and show hundreds of the same form if you wish, but calling a method on one of them wont affect the others (unless you make them static). – Alfie Sep 08 '13 at 17:23

Ehsan88 · Accepted Answer · 2013-09-08T20:40:48.303

As Alfie said, when you create a new instance of Form1 it has nothing to do with the current running instance which you could probably find created and run in Main method in Program.cs file in your solution:

static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1()); // THIS INSTANCE
        }

It would be better you become more familiar with Object Oriented Programming (OOP) if you have difficulty understanding this. In past programming languages like VB6 we only had one Form1. But in OOP like C# you could have thousands instances of Form1, more informally speaking thousands of Form1.

However perhaps the best solution to what you want to do is to change the default way of running Form1:

static class Program
    {
        public static Form1 myForm1;

        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            myForm1= new Form1 ();
            Application.Run(myForm1);
        }

    }

and use this to manipulate the instance:

Program.myForm1.AddToListView();

By the way, doing so seems quite unnatural to me in sense of OOP. Please add comments about any ideas you might have about this ?

I appreciate if the down voter tells me what's wrong with my answer? — Ehsan88, Sep 12 '13 at 17:36

Public method not triggered cross forms

2 Answers2