[C#] Is it possible to override the Form class?

[ProclaimDragon]

Sorry, forgot to say in the topic title that this is C#.

Let me explain what I want to do...

We all know that with Windows Vista brought a new UI font, Segoe UI, but XP still uses Tahoma as UI font. This doesn't help us programmers. I've searched in Google and what I found was to use SystemFonts.MessageBoxFont as the Form's font because all other controls Font properties will inherit from it.

Now, I could do this.font = SystemFonts.MessageBoxFont; before InitializeComponent(); on every single form I use but that will have 2 problems:

1) I'll have to repeat this line for every form.

2) The designer will not be updated accordingly.

If I moved this.font = SystemFonts.MessageBoxFont; into InitializeComponent() itself, then, the designer would be updated but I still would need to do it manually for every form.

My first solution:

Create a class (MyForm, for instance) that inherits from Form and change the properties I need in it's constructor. Then, every form I use in my application must be inherited from MyForm instead of Form. This is simpler than to place the line above in every InitializeComponent(), although, I still have to manually change every from to inherit from MyForm instead of Form.

To sum this up... I'm looking for a way (if possible) to change some default properties of Form without creating a new class that inherits from it, which allows me to make all the needed properties changes in one place and all my forms will still inherit from Form (as they are by default).

Is this possible?

Edited May 24, 2008 by Nazgulled

[ProclaimDragon]

Little desperate bump... :(

[azcodemonkey]

Just a thought, and not something I've sat and pondered, but maybe try to create a factory class that creates all your forms with defaults that you can configure via app.config.

[ProclaimDragon]

Not sure what you mean :(

[Antaris Veteran]

What he means is create a class with static methods that you use to create instances of your forms:

public static class FormFactory
{
	public static TForm CreateForm<TForm>() where TForm : Form
	{
		TForm form = Activator.CreateInstance<TForm>();
		form.Font = SystemFonts.MessageBoxFont;

		return form;
	}
}

and then you would use it as such:

Form1 myForm = FormFactory.CreateForm<Form1>();

[azcodemonkey]

Yep, that's what I mean. :) Thanks, Antaris.

[Antaris Veteran]

I got yo' back blood. :p

[ProclaimDragon]

Thanks for the suggestion and the whole code but that's almost like that I'm doing now... It's a different way of doing what I want but it's basically the same thing, what I mean is, I'll still need to manually create an instance for every form.

I may be looking for something that doesn't exist or it's not possible, but that's why I'm asking cause one doesn't know everything ;).

[azcodemonkey]

  Nazgulled said:

Thanks for the suggestion and the whole code but that's almost like that I'm doing now... It's a different way of doing what I want but it's basically the same thing, what I mean is, I'll still need to manually create an instance for every form.

I may be looking for something that doesn't exist or it's not possible, but that's why I'm asking cause one doesn't know everything ;) .

  Quote

To sum this up... I'm looking for a way (if possible) to change some default properties of Form without creating a new class that inherits from it, which allows me to make all the needed properties changes in one place and all my forms will still inherit from Form (as they are by default).

Is this possible?

I'm confused... The method Antaris illustrated allows you to modify all your forms in one place, and have them all keep Form as their base. I don't know what else you're expecting it to do.

[Antaris Veteran]

Nazgulled, I think you might be getting confused with what is actually going on with your Form types.

Although the designer allows you to (as its name suggests) design the form, the form is still instantiated manually in code, its just that the program generates the code to do so. The factory method I illustrated could be used with your designed forms too. Just change the line of code that usually says:

Application.Run(new Form1());

which is generally found in the generated Program.cs, to this:

Application.Run(FormFactory.CreateForm<Form1>;());

All you are doing is using the factory method to apply any property changes ahead of the instance being returned. It doesn't matter if you use the designer, the Form is still being declared manually.

[ProclaimDragon]

But your method is not very different from my own (inheriting from a sub classed form) and that's not what I was looking for...

If I have 100 forms I'll have to do 100 modifications either using your method or mine and that's what I was looking to avoid... I was looking for a one time global change only, if there was one...

What I'm saying is, using my method, I'll have to inherit all my forms from the sub classed form. Using your method, I'll have to use the FormFactory for every form but there are the type of things I was looking to avoid.

Maybe that's not possible at all, but like I said, I don't know everything, so I just asked...

[Antaris Veteran]

Well, if thats the way you want to do it, do the following:

public class SubclassedForm : System.Windows.Forms.Form
{
	protected override void OnLoad(EventArgs e)
	{		
		base.OnLoad(e);
		this.Font = SystemFonts.MessageBoxFont;
	}
}

What you are doing is subclassing the form and overriding the OnLoad method (this is not the OnLoad event, but the method that will call any event subscribers). What will happen, is that any class that inherits from SubclassedForm will call the OnLoad method (unless the inheriting form overrides the OnLoad method itself, in which case it will need to make a call to base.OnLoad(e)).

To be honest, my personal preference is to go with the Factory pattern, as I believe it is much more flexible.

[ProclaimDragon]

You misunderstood the point... I already knew how to do it with inheritance but that's not what I want. Both solutions force me to do lots of code changes (depending on the number of forms) but that's not what I want. I was looking for a way to do one time change only, without needing to change their base class or how they are initialized.

Like I said, I'm probably looking for something that's not possible so just forget about it. Cause I don't know how to explain myself better than this.

Thanks for all your time guys.

[Antaris Veteran]

Its not that I misunderstood the point, the fact is there isn't a one time change. The Form type is sealed. The Designer type is sealed. VS uses that designer to generate code. It won't automatically set the font, because this is inherited from the base classes. You either need to inherit from the Form type, or follow the factory pattern and set your properties in the one place.

[azcodemonkey]

  Nazgulled said:

You misunderstood the point... I already knew how to do it with inheritance but that's not what I want. Both solutions force me to do lots of code changes (depending on the number of forms) but that's not what I want. I was looking for a way to do one time change only, without needing to change their base class or how they are initialized.

Like I said, I'm probably looking for something that's not possible so just forget about it. Cause I don't know how to explain myself better than this.

Thanks for all your time guys.

If you have a refactoring tool, like Resharper, you should be able to accomplish the changes pretty easily, but I understand your apprehension. It's a lot of work manually, and a lot of regressions that could be introduced.

Good luck. :)

[ProclaimDragon]

  Antaris said:

Its not that I misunderstood the point, the fact is there isn't a one time change. The Form type is sealed. The Designer type is sealed. VS uses that designer to generate code. It won't automatically set the font, because this is inherited from the base classes. You either need to inherit from the Form type, or follow the factory pattern and set your properties in the one place.

That's exactly what I was asking :)

If that's how things works, I'm ok with it, I just wanted to know if it was or it wasn't possible.