Multiple forms Windows applications(questions)

Question

well I'm quite new to C# though i am well-acquainted to C/C++. What bothers me is: -ok I create a new Windows app project and I get stocked with Form1; I'll add to it the controls I need (e.g. a textBox1) yet I want to add a Form2 not programmatically but by the designer; -after doing that in Form1's code I add something like: Public Form2 f2=new Form2(); -but if I want to modify the text within Form1.textBox1 in f2's code like this: Form1.textBox1.Text=... a error message is issued: An object reference is required for the nonstatic field...textBox1. Why's that? P.S. : also I wrote: Form1.AddOwned(f2). Waiting for an answer.

An Vo · Answer

address: www.nobrainer.nl/csharp/CommunicatingForms.zip can not access Thanks

Mahesh Chand · Answer

Testing a reply

pavithran · Answer

Hi Can any one share the ZIP file plzzz nobrainer Can u upoad that the solution again plzzz Thanks pavi

bilnaad · Answer

The zip file is no longer on the server and is permanently deleted :( Maybe someone who downloaded the sample can share it with you? cheers

shamsuddin04 · Answer

hey. is it just me or is the zip gone? if it isnt just me could u plz plz plz upload again. thank you very much for your time.

bilnaad · Answer

newkid the answer is already in the solution on the server. The only thing you need to do is alter the functions in the interface based on what you want to do. if you get the hang of how interfaces work(like in the sample) you can figure out very easily what you need to do to get the functionality you want ^_^

wheezhacker · Answer

I am new to C#. Your solution almost answered my question. In my parent's form I click on my menu items Setup | New it will disable the New item on the toolbar before it opens my child form called setup_new so that the user won't be able to click on the Setup | New again to create the second child form. When I close my setup_new form I want to re-enable the New item on the toolbar in my parent's form. How can the child form re-enable this property that belongs to the parent form?

alobiuc · Answer

Well you made my day nobrainer! It works just fine (both matters you answered to). Thanks a lot. Hope I'll be hearing from you on further questions that may occur. Regards A.L.

bilnaad · Answer

When you let the Form to a static member you can modify this object from anywhere. This can come in handy but only objects that needs some kind of reference to the Form object should be able to use it. Now it can be accessed from anywhere and it's a good target for errors or unwanted behavior(because other classes are playing with it). Only when you are being very carefull you could use the static object. But it's not so wise to do so ^_^ 1. Let me explain The interface ICommunicate can be expanded to contain several more functions. Just whatever you need. When an object inherits the ICommunicate interface this object MUST implement these methods. Else you would get a compile error. So when objects MUST implement the methods they can be recognized of certain functionality. So when you want the object that inherits ICommunicate to implement a function to change the text of that object you could add a function prototype to the interface. Like: void ChangeText(string newText); Also the ICommunicate interface can be inheritied in any object. If you want have the interface functions implemented in the parentform so that all childforms can access that functions it could inherit the interface implement to functions and your done. 2. I've done this some time ago. So I maybe wrong about some parts ^_^ Every Control has this function this.CreateGraphics(). You could store the Graphics object in a variable like: Graphics g = someControl.CreateGraphics(); So then you have access to the many functions the Graphics class has to draw stuff on the control. No matter what kind of control it is. But I think for some controls you need to enable a property like OwnerDraw or something(not sure). I hope this covers most you wanted to know. Good Luck

alobiuc · Answer

Oh and maybe you'll be so kind to answer me why is it wrong to declare the parentform as a static member.

alobiuc · Answer

Well that's something else indeed. It works out just fine. Still I have two questions: 1. how do I access a parent method (instead of a control) from the child form using (or not)ICommunicate? 2. on a form how can I draw something (circleline etc.)? In the .Net help files it only shows how to draw something on a control a not-so-simple procedure. I just wanna draw something somewhere control-independent. And thanks for your efforts in making me understand better C#. A.L.

bilnaad · Answer

Now you can get thye reverse of my other sample at www.nobrainer.nl/csharp/CommunicatingForms.zip What it does is access the childs parent and get a control from the parent to play with. I hope I got it right this time :)

bilnaad · Answer

Just wait I will make another example to simplify things ^_^

alobiuc · Answer

I'm sorry to tell you but none of the solutions doesn't seem to work. In the first case: assuming Form1 is the main form and Form2 the child: public class Form2 : Form { internal parent=null -> results in an error mesage (Invalid token '=' in class...declaration) public Form (Form parent) { this.parent=parent; } } Further more when declaring: public Form Form2=new Form(Form1) also leads to: Form1' denotes a 'class' where a 'variable' was expected. Hopefully I didn't get it right. As a question: in what way am I mistaking making parent form be contained in a static function? Does it affects in any way the program's performance? Sorry for bothering! Yours A.L.

bilnaad · Answer

Also I always use interfaces to access certain forms when I don't know(or don't wanna know) what the exact classname is. If the Form has ICommunicate implemented your sure that that Form object contains certain function wich you can use. This way you don't have to know if it's a Form1  Form2 or Form3 you can just reffer to it as a Form. I hope this helps you in finding a decent solution ^_^ Regards

bilnaad · Answer

Ah I see ^_^. But let me make one last remark ^_^. You code as making the parentform be contained in a public static function is no good programmingpractice. Although it works ^_^. A more elegant solution would be to add a parameter to the childforms constructor. If the childform is instanciated you can pass in the form that should be considered as the parent and store it in a private/internal variable in the childform. Something like: class ChildForm : Form { internal parent = null; public Childorm(Form parent) //or (MainForm parent) or something ^_^ { this.parent = parent; } } This way you have always access to the parentform.

alobiuc · Answer

Thanks NOBRAINER the code is indeed understandable and it proved to be useful to me in certain matters. Yet your code explains how a parent form can send data to child forms; my problem WAS (I finally figured it out as I 've shown in my previous post) how can a child form access members belonging to the parent form. Once again I appreciate posting that zip file.

bilnaad · Answer

A.L. I've uploaded a little sample on my server. I don't want to paste to much code in the forum so it results in one large blob of code inhere ^_^ the url: www.nobrainer.nl/csharp/CommunicatingForms.zip I made a little sample that uses interfaces. I hope the code is understandable. If something is not clear please ask ^_^ Regards

alobiuc · Answer

Regarding my last post: think I've solved the problem and the answer might interest other C# newbies: -in Form1's code add: public static Form1 f1; -assuming that main is in Form1 and it looks like: static void Main() { Application.Run(new Form1()) } replace it with: static void Main() { Application.Run(f1=new Form1()) } Now one should be able to access any method or property belonging to Form1 like this: Form1.f1.textBox1.Text=... or Form1.f1.Hide() etc. However I'm waiting for better ideas from anyone.

alobiuc · Answer

OK I got the idea of passing an reference of Form1 to f2; the remaining question is: HOW do I do that?

bilnaad · Answer

You need some kind of reference to the Form. How you add that reference is another thing.