A Bug Related To Form Constructor

mahesh waghela

15y2.9k

Passing a reference to the Form Constructor is it a bug?

e.g.

Form4 form4

Public Form1(Form4 form4)
{
this.form4=form4
Initializecomponent();
}

I want to draw the attention of our community members to the confusion surrounding the passing of references into form constructors. I am always against passing a reference to the form constructor.

It is important to know what is a Form Constructor before preparing to write a big project.

According to the MSDN article:

The Form Constructor "Initialises a new instance of the Form class"

I think we can all agree on this definition. Knowing this I want to ask is it bad practice to pass a reference to the Form Constructor in large projects? And Is it a Bug To Write A Reference To The Form Constructor?

The reason I ask is because in big projects a particular form is not stand alone. It may have many relationships with other forms up to 10,20 or even 30+. So passing a reference to Form Constructor causes an "overload method error."

26 Replies

Know the answer? Post it — somebody with the same question will find it here.

mahesh waghela15y ago
OK Every Body

Now I hereby End my Discussion as there are nobody has time to discuss it. Even I agreed that my discussion is useless.

Thanks Every Body.
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Sam Hobbs15y ago
Vulpes did not suggest a three-tier solution; I did.

You asked for guidance and we provided it. I don't have time to argue. You need to spend time learning.
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mahesh waghela15y ago
Vulpes,

This is much better way also, but can you tell me that why I have to prefer your three tier solution and why not I have to prefer my own solution?. What is the deference between those two solution?.
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mahesh waghela15y ago
Ok
Sam Hobbs

Agreed with your comments about passing a parameter to Form Constructor is good thing. Now tell me one thing that here in my post of three tier example in where a parameter is passed is it good thing?.

1. If it is Good thing than why not I have to prefer it(my three tier example)?. Why you tell me to looks to other option?.

2. Is there no Action & Reaction of passing a parameter to Form Constructor?. If it is no than why you have to do extra job with "Overload Method Error" between multiple forms?.

3. Is there always dependency of two or three forms in a project?. If So than it is good thing other wise not.

As per my knowledge the forms is not container of data but it is container of controls and the other controls are containing the data. The other controls means textBox/Label/DGV/Listview etc.

Here to pass a parameter in Form Constructor is like Doctor's treatment. Where patients having complaints of fever and he prescribed for it and what happen the fever is gone but the other complaint starting due to reaction of medicine. The same thing goes here that the previous problem solved and the new problem start.

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Sam Hobbs15y ago
I am sorry if I was not clear. I think that passing a parameter to a form constructor can be a very good thing; it depends on what is being passed.
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mahesh waghela15y ago
Sam Hobbs

I also do agree with you as why am always against to pass a reference as parameterized at form constructor. and same I am discussed here that what is form constructor and what are you doing with it. it is the bad idea to pass parameter into form constructor.
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Sam Hobbs15y ago
In addition to errors at compile time and at run time are errors shown in the editor. C# can identify many problems in the editor and that makes it even easier to fix them. Run time errors are different since we need to (should) write code to deal with them and they affect the use of the program.

A lot of this discussion is the result of the use of forms as a container of data. Forms are a UI and a better design is to separate the data from the UI. That would be a very useful thing for Mahesh and other beginners to understand. The C# IDE seems to have been designed by programmers that are not experienced with object oriented programming; perhaps they are former VB 6 programmers. In C++ Microosft has MFC and the IDE for it supports classes for documents separate from the UI.

Mahesh, look for articles about three-tier architectures. There are similar design methodologies with other names. A three-tier architecture has a UI, a data layer and a business layer. For simple programs, that could be reduced to a UI and data. Try to look for articles in this web site about things like that. I am embarrased to admit that I am unsure of the details of how it is done in C# but I assume that it would be very typical for the data to be passed as a parameter for the form constructor.
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Vulpes15y ago
Although that works, passing delegates to the constructors is a cumbersome way to do it.

Here's the same code but using (say) a static field to expose a reference to Form1 to the other two forms:

public partial class Form1 : Form
{
public static Form1 Me;

public Form1()
{
Me = this;
InitializeComponent();
}

private void Form1_Load(object sender, EventArgs e)
{
textBox1.Text = "Beautiful World";

}

public void Mytext()
{
textBox1.Text = "";
textBox1.Text = "My Beautiful World";
}

private void button1_Click(object sender, EventArgs e)
{
Form2 f2 = new Form2();
f2.Show();
}

}

//Form2 Class:

public partial class Form2 : Form
{

public Form2()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
Form1.Me.Mytext();
this.Close();
}

private void button2_Click(object sender, EventArgs e)
{
Form3 f3 = new Form3();
f3.Show();
this.Close();
}

}

// form3 Class:

public partial class Form3 : Form
{

public Form3()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
Form1.Me.Mytext();
this.Close();
}
}

The functionality is the same but it's much simpler and easier to understand.

If you introduce further forms, then they can likewise call:

Form1.Me.Mytext();

without further ado.

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mahesh waghela15y ago
Ok
Vulpes

Here I brings to you a small project of a passing a reference as a parameter of delegates into form constructor:

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

private void Form1_Load(object sender, EventArgs e)
{
textBox1.Text = "Beautiful World";

}

public void Mytext()
{
textBox1.Text = "";
textBox1.Text = "My Beautiful World";
}

private void button1_Click(object sender, EventArgs e)
{
Form2 f2 = new Form2(Mytext);
f2.Show();

}

}

//Form2 Class:

public partial class Form2 : Form
{
public delegate void myaction();
myaction MyAction;

public Form2(myaction MyAction)
{
this.MyAction = MyAction;

InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
MyAction.Invoke();
this.Close();
}

private void button2_Click(object sender, EventArgs e)
{
Form3 f3 = new Form3(ff3);
f3.Show();
this.Close();
}
public void ff3()
{
MyAction.Invoke();
}
}

// form3 Class:

public partial class Form3 : Form
{
public Form2 form2;

public delegate void bigbang();
bigbang BigBang;
//publc event bigbang btt_click;

public Form3(bigbang BigBang)
{
this.BigBang = BigBang;
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
BigBang.Invoke();
this.Close();
}
}

The above project is for a calling MyText() Method of form1 from form2 and form3. and it's works well both forms calling method perfect on button click event.

Now the question is If some other forms may have to contact or have to visit by making of instance than what they have to do they have to pass unnecessary reference even they not have any concern about it. the form2 and form3 relation with other form may be more than 20 or 30 than what you have to do with it?.

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Vulpes15y ago
It's much better for errors to occur at compile time, so that they can be corrected whilst the application is being developed, rather than at runtime. Indeed, this is one of the reasons why 'strongly typed' languages such as C++, Java and C# are so popular amongst professional programmers.

Although some runtime errors will show up during testing, the worry is that other runtime errors will not show up until after the application has been shipped to the user. Such errors are not only a nuisance to correct but may lead to the user losing confidence in the application if there are a number of them. So, the more errors you can discover at compile time the better.

As I said in my last but one post, which method you choose to pass references between forms depends on the circumstances. There's nothing intrinsically wrong with any of them.

If one form will only ever need a reference to another form but may use that reference a number of times, then passing a reference to the second form in the first form's constructor, may make sense.

If you have a lot of forms which may need references to several of the others, then passing references in the constructors might be too cumbersome and using Application.OpenForms (which, in effect, is a global collection) might then be preferable.

The important thing is to be aware of the techniques which are available to you and then choose the best one for the job in hand.

Incidentally, you're not creating new instances of forms with any of these techniques - you're simply obtaining references to existing instances.
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mahesh waghela15y ago
true Vulpes

I also agree with you as because I have also argue "the global variable are bad?" at "Stack-Overflow" the link is not available to me because it's removed and I have got success about it that it is easiest way to communicate between multiple form and it's not affect at c#. but it's past.

But I am not agree with you at pass parameter at form constructor causing "overload method Error" subject. And You called it a "compiler error" not "run time error". in this case I want to ask you that what is the deference between compiler error and run time error. The compiler error can be debug even run time error also can be debug. So why you give importance to run time error why not to equal?.

If one form has many relation with other forms it may be 10,20 or 30+ and each form having instance of main form about 4 or 5+ than you mean each time I have to pass a reference into form instance and for that I have to create the object of third party form. is it good practice?.

Error is Error than what it may be run time or compiler.

I am not ready to do this type of over loaded work and hence I am against of to do extra job with concern it.

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Vulpes15y ago
No, it's not wrong though you need to add one or two semi-colons for it to compile. The only time when you'll get the "No overload for method 'X' takes '0' arguments" error is if you try to construct a Form4 without passing it a Form1 reference and it'll be a compile time error, not a runtime error.

C# doesn't have global variables as such because all variables have to be defined within a class or struct.

The closest we have to global variables is public (or internal) static fields or properties of static classes. Many of the reasons why global variables are bad in some other OO languages don't apply to their C# counterparts because we can control access, make them read or write only, do constraint checking etc. in much the same way as we can do for a non-static class.

I personally have no hesitation in using a global variable if that's the easiest and most natural way of doing what I want.
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mahesh waghela15y ago
Sorry Vulpes it's my bug.

So you are saying to pass a reference to the form constructor is not wrong by below way.

Form4 form4

Public Form1(Form4 form4)
{
this.form4=form4
Initializecomponent();
}

So It's not causing "Overload Method Error" on further instance of it for other relative forms.

and here you arise a new question about to pass static variable. Do you not think about passing global variable are bad. Here I disclose the article which describe how global variable are bad?. The Link is : http://c2.com/cgi/wiki?GlobalVariablesAreBad.
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Vulpes15y ago
The 'internal' modifier means that it's only visible to other classes within the same assembly and has been in C# since version 1.0. However, if you're not comfortable with it, just use 'public' instead.

There is nothing wrong with passing a reference in the constructor or obtaining one in either of the two other methods I've described. Which one is best depends on the circumstances of your application.

If you have a lot of forms that require references to each other, then Application.OpenForms has the merit of not requiring the constructors to be changed or static fields or properties being added to each form. For example, if Form4 requires a reference to Form1, it can get one like this:

Form1 f1 = (Form1)Application.OpenForms["Form1"];
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mahesh waghela15y ago
Vulpes,

May be you wright on your idea. I have no idea about "Internal" Modifier because I think it is not in .Net 2.0 Version and I am using it. hence I have not tested your code.

But once again here I am remind you that passing a reference like above way is it correct?. You have applied here different way than me. It is advance version code hence I can't say anything about it.
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Vilas Gite15y ago
Thanks Vuples Sir.....
Its really nice info for me... which is not explain in brief in my class room.
:)
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Vulpes15y ago
There's nothing wrong with passing a reference to a form to another form, via its constructor, if the second form will be accessing the first form or its controls.

However, if you have several (non-MDI) forms and the forms may need to access one another, then you may find it easier to use the Application.OpenForms collection (see http://msdn.microsoft.com/en-us/library/system.windows.forms.application.openforms.aspx) which, as its name suggests, enables you to obtain a reference to any other form which is currently open in the application.

Another way that forms can easily expose references to themselves is via an internal static property:

partial class Form1 : Form
{
internal static Form1 Me;

public Form1()
{
Me = this;
InitializeComponent();
}

// rest of form code
}

Another form can then get a reference to the Form1 instance using this code:

Form1 f1 = Form1.Me;

This is OK as long as you only ever create a single instance of your forms.
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mahesh waghela15y ago
Feel Good to see all of you here in important discussion.

I am Well-Come Vulpes, Sam Hobbs,Pradeep Chandraker, and Vilas Gite Here we are discussing about form constructor's bug.

I am request all of you to consider my edited question once again. Where I am suggested why I am against of passing a reference to the form constructor. The question is not about how you call form reference to the other forms. but the question is that if you have three form and you want to call the method of particular one form from two forms. And you have passed the reference of forms into form constructor and call it perfectly and it's works well too. Than what happen that if form1 has more relation to other forms and whenever we make the instance of form1 than it's cause to "Overload Method Error".
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Sam Hobbs15y ago
Your code is not correct code; you will get many errors if you try to compile the code you posted here.

I sure don't understand what it is that you think is a bug. Do you think it is a bug because the constructor has a parameter or is it a bug because the constructor is like that or something else?
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Vilas Gite15y ago
hi Mahesh...
as per replies of Vulpes sir and pradeep Sir,
There are some rules..........
--------------------------------------
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Pradeep Chandraker15y ago
It is not a bug. You can pass any class object to any constructor. The Form is also a class to same rules applies here too.

The question here is how are you calling Form1? does it has default constructor?

It will be good if you can provide complete code sample which is causing this error.

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Vulpes15y ago
I always take questions seriously unless it's clear the OP doesn't intend them to be.

The chance of there being a bug in simple Windows Forms code is extremely remote.

However, I can't tell whether there's a bug or not without knowing how you're calling the constructor.
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mahesh waghela15y ago
hi
vulpes

don't take it lightly it's a serious question. Here I am asking for is it bug or not?
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mahesh waghela15y ago
hi vilas gite I am not asking for solution. here I am asking is it bug or not?
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Vulpes15y ago
I don't know how you're actually calling this constructor but you should be doing it something like this:

Form4 form4 = new Form4();
Form1 form1 = new Form1(form4);
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Vilas Gite15y ago
hi mahesh
i think you have error description..
"No overload for method 'Form1' takes '0' arguments"
please check this:
http://www.dreamincode.net/forums/topic/68275-no-overload-for-method-mainform-takes-0-arguments/
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