call an opener form method

mabrahao

hi guys, i have a form that needs to call a function on his opener form. How can i do this? ex: form1 opens form2, and form2 needs to call a method in form1. thanks a lot!

Paladin2000

Make the method public, and pass a reference to itself to the second form (in the second form's constructor).

*** In Form1 ***
Form2 form2 = new Form2(this);

*** In Form2 ***
public Form2 (Form1 form1) : this()
{
_form1 = form1;
}

private Form1 _form1;

mabrahao

i've used From2 f = new Form2(ref Form1 this); but didnt work.

Paladin2000

This works for me. Two forms, one with a button and textbox (Form1), the other just a button (Form2).

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void button1\_Click(object sender, EventArgs e)
{
    Form2 form2 = new Form2(this);
    form2.Show();
}

public void Change(string text)
{
    textBox1.Text = text;
}

}

public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}

public Form2(Form1 form1) : this()
{
    \_form1 = form1;
}

private Form1 \_form1;

private void button1\_Click(object sender, EventArgs e)
{
    \_form1.Change("Put some text in the TextBox");
}

}

Blue_Boy

you can do it something like: using(Form2 frm2 = new Form2()) { frm2.myVoid(); }

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mabrahao

ok, almost there... i got only one more problem... i need to pass 2 param to my form2. ex: From2 form = new Form2(id, this);

Paladin2000

Just change the constructor... Simple.

public Form2(int id, Form1 form1) : this()
{
_id = id;
_form1 = form1;
}

private int _id;
private Form1 _form1;

mabrahao

solved... just removed the : this(). anyway... thank you very much

Paladin2000

The this() call makes the constuctor call the lower-level constructor overload. In this example, Form2(Form1 form1) : this() causes it to call public Form2() during its execution, which thereby causes it to call InitializeComponent(); (and anything else inside Form2()). If you don't have a parameter-less constructor overload of course, it will fail. ;)

public Form2()
{
InitializeComponent();
}

public Form2(Form1 form1) : this()
{
_form1 = form1;
}

dan sh

Either do the way others have suggested or follow on of the following approach: 1. Create a class called Common or something similar and place the methods used by more than one forms there. Then all the forms can call methods in this class. Or 2. Have a base class that contains common methods (possibly marked virtual) and all forms in your application inherit from that class.

"Your code will never work, Luc's always will.", Richard MacCutchan[^]

Luc Pattyn

your answer is not clear at all. If this is a third form you are creating, it is wrong as it would not share anything with the original Form it is trying to interact with. :|

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fjdiewornncalwe

I never like solutions that include a child knowing about its parent. I question whether the UI forms should be communicating directly in the first place and if some re-architecturing needs to take place on that design. But suffice to say, if the forms do need to communicate, I would much rather see it done where Form2 raises an event for which Form1 creates a handler when creating Form2. That way, at least the child still knows nothing about the parent. if( eventToCall != null ) eventToCall();

I wasn't, now I am, then I won't be anymore.

Paladin2000

With events instead, it could look something like this. (Probably better to pass the message in an event argument, though.)

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
form2.Clicked += new EventHandler(form2_Clicked);
}

private void form2\_Clicked(object sender, EventArgs e)
{
    textBox1.Text = form2.Message;
}

private void button1\_Click(object sender, EventArgs e)
{
    form2.Show();
}

private Form2 form2 = new Form2();

}

public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}

private void button1\_Click(object sender, EventArgs e)
{
    Message = "Here is some text";
    if (Clicked != null) Clicked(sender, e);
}

public string Message = string.Empty;

public event EventHandler Clicked;

}

[Edit] Public to private on Form2.

modified on Wednesday, January 5, 2011 1:31 PM

fjdiewornncalwe · modified on Wednesday, January 5, 2011 1:31 PM

In theory correct, but there may be a few issues. public Form2 form2 = new Form2(); should probably be made a private member unless it it required by something outside this form.(That would likely not be a good idea) Other than that, I think it is pretty close.

I wasn't, now I am, then I won't be anymore.

Paladin2000

Did I say public? I meant private... :-O :-D

Paladin2000

Might as well give the "event" version that passes the string as an event arg...

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
form2.Clicked += new Form2.StringEventHandler(form2_Clicked);
}

private void form2\_Clicked(string message)
{
    textBox1.Text = message;
}

private void button1\_Click(object sender, EventArgs e)
{
    form2.Show();
}

private Form2 form2 = new Form2();

}

public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}

private void button1\_Click(object sender, EventArgs e)
{
    if (Clicked != null) Clicked("Here is some text");
}

public event StringEventHandler Clicked;
public delegate void StringEventHandler(string message);

}

fjdiewornncalwe

Hide your members whenever possible... Showing them almost always leads to embarrassment and ridicule... :)

I wasn't, now I am, then I won't be anymore.