Sharing Data between two forms

Hello Friend,

That is just a sample to show how to use delegate in your scenario
, it can be handled .

Thanks,
Narayan

Hi Naraya,

I tried your example program, it works but only problem I noticed is that , Open Form 2 button when clicked creates a new instance of Form 2 regardless whether Form 2 is already created or not. This mean if one clicks that button repeatedly soon there will be dozens of Form 2.

Anyway, will check the delegate concept more in deep, sounds to be more cleaner method .

Thanks once again.

Regards
 

Thanks Narayan,
Sounds interesting, will check this and share my finding with you.

Regards

Babali
 

Thanks Sam for the inputs.

I have a small doubt here , when I create a FORM 2 but keep it  hidden means we are consuming System Resources when it is not needed , is it correct?


While on the same topic, earlier I attempted making FORM 1 as parent and FORM 2 as a child, that worked but only problem was FORM 2 always showed behind some controls on FORM 1 , a picture box, FORM 2 always used to get behind that picture box.I could never get FORM 2 at front, so decided to drop MDI scheme. Do you have any suggestion on this?

Regards

Babali 

Hi
You can use delegate to hold a reference to that method used for updating data. Its more cleaner way of doing these kind of things.
Please take a look at the attached sample.

I have two forms form1 and form2
form1 has a combobox and button, click the button 2 to open form2.
When you change combobox item, those text will be changed in form2.

Thanks,
Narayan

I am not sure what you are doing so I am not sure if my suggestion will work for you, but what I would do is, in form 1, create an instance of form 2 except the default for form 2 would be that it is hidden (not visible) initially. Then when form 2 is to be shown, I would make it visible and then when it is closed, I would actually just make it hidden again but not closed. That way, there will always be an instance of form 2.

If you want to do it the way you are doing it (using Application.OpenForms) then you can execute Application.OpenForms without casting to FORM2. Then check the return value of Application.OpenForms and if it is null then you know not to use that value. If it is not null then it is safe to assume there is not a problem so you can next cast the return value (from Application.OpenForms) to FORM2.

Thanks for the suggestion.
In the mean time I tried something which worked , but I am a bit skeptical about the approach. Please guide me.

What I am doing is:

FORM 2 which displays the Message string, is instanced as:


public string messageIn;

public FORM2(string myMessage)
messageIn = myMessaage; // input string to on FORM public variable


In FORM 2 I have a public method:

public void ShowMessage(messageIn)

I call this ShowMessage in the form_load method:

private void FORM2_Load(object sender, EventArgs e)
{
ShowMessage(messageIn);
}


In FORM 1 , have to call this ShowMessage in FORM 2 so that update message gets displayed on FORM 2.

There are two possibilities:

1> FORM 2 is not yet instanced
If it is not instanced , I don't bother.
 
2> FORM 2 is already instanced, then I must update it.

So check that part first as:

  In FORM1:

bool IsOpen = false;
foreach (Form f in Application.OpenForms)
{
if (f.Text == "FORM2")
{
IsOpen = true; // FORM found
break;
}
} // Loop to check next FORM

// If FORM2 is already instance then and then only update
// If FORM2 is not instanced , no need to update
if (IsOpen == true)
{
// FORM2 already instanced , OK to update it
FORM2 f1 = (FORM2)Application.OpenForms["FORM2"];
f1.ShowMessage(message);

}

When user Clicks on the button on FORM1 to view message, I first check first the whether the form is already instance or not.
If it is there already, I call the the method in FORM2, else I instance the FORM2 as:

FORM2 frm2 = new FORM2(message);// message goes as FORM2 constructor input argument

frm2.Show();


I am a bot worried the use of:
 
FORM2 f1 = (FORM2)Application.OpenForms["FORM2"];

Is it safe (legitimate) or it might pose some potentail problem later?

Regards

Babali