Copying a Form

[Aads]

Hi there,

Is there any method or a way to copy a form object to a variable?

Let me explain this - We have a method called "Copy" for the Dataset class & you all must be knowing that there is a difference between the below two lines of code:

                 DsTemp = Ds 
                 DsTemp = Ds.Copy()
 

In the first line of code, any changes made to Ds will reflect in DsTemp. However, in the second line of code, any changes made to Ds will not reflect in DsTemp because we are only "copying" the contents & schema of Ds. Likewise is there a method or a work around to "copy" a Form object?

Thanks in advance,
Aads




- please see the below code:

 Dim Ds as Dataset
                 Ds.ReadXml("C:\MyXml.xml")
                 Dim DsTemp as Dataset = Ds.Copy()

[r035198x]

Controls don't seem to be Cloneable by default in .NET.
Perhaps this article may help?

[Aads]

Thanks for your help - that article did help me to explore about controls but the same doesn't apply for windows forms.

[Xennex]

When I first used VB.NET the only way you could get a form was to define it first. For example if I had designed a form with the name "frmMenu" I would have had to create an instance of it first by DIMming it first. "dim myForm as New frmMenu" Then I would have to use myForm in all my further code. Now it seems you can use the classes like you could back in VB6 by just referencing them and letting the compiler create a new object automatically.. I believe if you dim a variable of type <your form class> with the New keyword like above, you should be able to create any number of objects of your form class, each with it's own set of properties that can be changed independent of any other object of that form class.

[vekipeki]

Why would you like to deep copy a Form object? You can create as many instances of a Form and display them simultaneously, but the actual data those forms are displaying doesn't have to be the same.

For example:

MyForm f1 = new MyForm()
f1.SomeData = myData.Clone(); // this will create a new copy
f1.Show();
 
MyForm f2 = new MyForm()
f2.SomeData = myData.Clone(); // this will create a new copy
f2.Show();
 
// etc.
 

What exactly are you trying to achieve, is there some data in your Form's properties that you would like to copy?

[Aads]

Thanks for your reply - yes you are right; I've some data in my form which I want to preserve for subsequent uses. Let me explain you this with the help of below code snippet - please see the below code:

 
Dim _listOfForms As New List(Of Form) 'List to hold data of type Form.
Dim _theFormChild As FormChild 'An instance of a child form
 
Private Sub OpenChildForm()
   _theFormChild = New FormChild '--------> (1), See below NOTE after this code snippet
   _theFormChild.MdiParent = Me
   _theFormChild.Show()
 
   _listOfForms.Add(_theFormChild) 'Add it to the generic list.
End Sub
 
Private Sub OpenStoredChildForm()
   _listOfForms(0).Show() ' This doesn't open up a form. (quite obvious!)
End Sub
 
 

NOTE: As Soon as the control reaches the constructor of the child Form, lots of statements are executed. For ex:
(a.) I instantiate around 8 classes which reads xml files of around 10 MB each. After it has read, it stores the data in the SortedList.
(b.) Next I instantiate 5 modal forms which in turn again instantiates some other classes.
(c.) Once the above tasks are done, I store (a.) & (b.) as properties of child Form i.e. as long as I've access to my child Form, I can happily access these properties as well.

Now this process takes around 7 seconds to complete which happens everytime whenever the user hits a button in the form. All I want to do is whenever the user hits the button for the first time let this process go on (as it needs to if I want to store somewhere or even otherwise) but when he hits the button for the second time instead of initiating this process again from scratch I want to access this data where I would've stored (which is what is required).

Is there a way where in I can store my child Form once it completes instantiation so that I can reuse the same Form whenever the user requires it thereby saving lot of time.

Cheers,
Aads

[Xennex]

So you just need to have the child form available to use but not visible? If so you could simply hide the child form using its "Hide" method. All parts of the child form are still accessible until you unload the child form.

[Aads]

Thanks for you quick reply. No I do not want the child form available just to use its properties. While this child Form is opened, if the user opens another copy of this form (without closing the one which is already opened), a new form opens going through all the process which I mentioned in the previous post thereby taking lot of time & this is what I do not want which is time consuming. All I want is that when the user opens the form subsequent times, it should open instantaneously with all the properties set (some how).


Cheers,
Aads

[vekipeki]

Instead of cloning the Form, consider cloning the Form's data. For example, you already have a ChildForm constructor like this:

public ChildForm()
{
    InitializeComponent();
    // do lots of xml work
}
 

and then you have a ChildForm property with large quantities of data:

private MyDataClass LargeData
{
    get { return this.largeData; }
    set { this.largeData = value; }
} 
 

So, all that you need to do is add a parameterized constructor which accepts MyDataClass, or event ChildForm as input:

public ChildForm(ChildForm otherCopy)
{
    InitializeComponent();
    // instead of doing xml work, just copy the data
    // (note that we can access private properties in
    // otherCopy instance)
    this.LargeData = otherCopy.LargeData;
 
    // or this.largeData = otherCopy.LargeData.Copy(); if you want a deep copy
}
 

Then you can create a form by calling this constructor:

ChildForm c = new ChildForm(someOtherForm);
c.MdiParent = this;
c.Show();
 

I just realized you're using VB.NET -- sorry. You should probably get the general idea.

Also, it is up to you to decide whether you want to Clone the data (make a separate deep memory copy), or just pass the reference to the same instance.

[Aads]

Hey thanks for your reply. I tried the technique suggested by you (storing xml data in properties & accessing it when required) - it worked absolutely fine. But could you please tell me what exactly "deep copy" means?

Cheers,
Aads