returning array from modal form

Thomas

I've tried searching and the only thing I can find is passing data to a new instance of a form.

I have an open form that opens a modal form. On that Modal form, a dynamically created a array is build and I need to return that value to the original form that is open.

I've passed data between MDI forms using parent and child but those are null on this modal form. I was able to set the open form to be the Owner of the modal form but that does not appear to give me access to the public variables on that open form.

I've tried ref and out in the constructor but then I get out of scope errors when I try to access that variable outside the constructor.

on form1 (open form) I have a public string array and the following code:

            frmAttachments cAttachments = new frmAttachments();
            cAttachments.StartPosition = FormStartPosition.CenterParent;
            cAttachments.ShowDialog(this);

on form2 (Modal form) I have the following code:
        private string[] Attachments = new string[1];

        public frmAttachments()
        {
            InitializeComponent();
        }

        {
            Other buttons and code to build Attachments Array.
        }

        private void btnDone_Click(object sender, EventArgs e)
        {
            this.Close();
            //At this point I need form1 to have the 'Attachments' string array values.

        }

Any suggestions?

8 Replies

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Frogleg14y ago
Accepted answer
Another way is to use delegates
Vulpes14y ago
No there are no downsides to using delegates for inter-form communication which many programmers prefer as they regard it as a more OO approach than the other techniques which are commonly used.

So, if that seems simpler to you, I'd go with that.
Thomas14y ago
Vulpes, Duh... I've step though the child forms in several other areas I should have realized that.

However. the delegates approach (modal zip file) was actually much simpler and I suspect more efficient. Once I got that project setup so I could see it in action.

I would be interested to know if there are downsides or things to be aware of with the delegates approach.
Thomas14y ago
I was able to open the cs fiels so I'm building a project to see what it is doing.
Vulpes14y ago
Suppose the MDI Parent form class is called Parent. Then the following code might work:

private void btnDone_Click(object sender, EventArgs e)
{
Parent p = (Parent)this.Owner;

foreach(Form f in p.MdiChildren)
{
if (f is Form1)
{
Form1 f1 = (Form1)f;
f1.Attachments = this.Attachments;
break;
}
}

this.Close();
}
Thomas14y ago
Frogleg, that was made with a newer version of VS. I have 2005 and 2008 and both tell me it was created in a newer version and I can't open it.
Thomas14y ago
Vulpes,
SOOO VERY Close!!! When I run it I get an error because it is the wrong form as the owner.

Form1 is an MDI child and stepping through the code it looks right but when I get to the Modal form the Owner is the MDI Parent form not the Child form that sent it.

cAttachments.ShowDialog(this); // Here in the code stepping though, 'this' appears to point to the proper child form

I threw a messagebox into the form load and at that point the owner is the MDI Parent form. It is trying to cast 'this' as the wrong form and it gives me an error.
Vulpes14y ago
The trick is to cast Form2's Owner to Form1 to get access to its public variables. If say Form1 has a public variable called Attachments of type string[], you could do this:

private void btnDone_Click(object sender, EventArgs e)
{
((Form1)this.Owner).Attachments = this.Attachments;
this.Close();
}