C#•6mo ago

Acces data from another form

I don't understand why in this example it doesn't show the name of the car, if someone can explain it to me in more detail or tell me how to make it work. It only appears that,, the car is,,. Thank you very much! https://paste.ofcode.org/35K3CPDgRTAqSEnwsaWGB57

72 Replies

leowest•6mo ago

because car on Form2 is a complete new instance of car you are creating 2 separated instances of car on each form

MODiX•6mo ago

leowest

REPL Result: Success

var a = new FormA();
a.Print();
var b = new FormB();
b.Print();

public class FormA
{
    private Car car;
    public FormA()
    {
         car = new Car("Porchse");
    }

    public void Print()
    {
        Console.WriteLine(car.Name);
    }
}

public class FormB
{
    private Car car;
    public FormB()
    {
         car = new Car("BMW");
    }

    public void Print()
    {
        Console.WriteLine(car.Name);
    }
}

public record Car(string Name);

var a = new FormA();
a.Print();
var b = new FormB();
b.Print();

public class FormA
{
    private Car car;
    public FormA()
    {
         car = new Car("Porchse");
    }

    public void Print()
    {
        Console.WriteLine(car.Name);
    }
}

public class FormB
{
    private Car car;
    public FormB()
    {
         car = new Car("BMW");
    }

    public void Print()
    {
        Console.WriteLine(car.Name);
    }
}

public record Car(string Name);

Console Output

Porchse
BMW

Porchse
BMW

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leowest•6mo ago

in order to share the same instance of car between both forms you need to pass that instance of car from FormA to FormB, be it via calling a method or other means. The most common way is called dependency injection, where u pass it via the constructor as a requiriment of the FormB.

public class FormB
{
    private readonly Car _car;
    public FormB(Car car)
    {
        _car = car;
    }

    public void Print()
    {
        Console.WriteLine(_car.Name);
    }
}

public class FormB
{
    private readonly Car _car;
    public FormB(Car car)
    {
        _car = car;
    }

    public void Print()
    {
        Console.WriteLine(_car.Name);
    }
}

and to pass it you would do something like:

var formB = new FormB(car);
formB.Show();

var formB = new FormB(car);
formB.Show();

@Ale does that make sense to u?

AleOP•6mo ago

OMG it s works sjdnfsakdfjnsakf , how i find this in internet to seach dependecy injection thank you soo much

leowest•6mo ago

$di

MODiX•6mo ago

Dependency injection is really just a pretentious way to say 'taking an argument' See: http://blog.ploeh.dk/2017/01/27/dependency-injection-is-passing-an-argument/

Dependency injection is passing an argument

Is dependency injection really just passing an argument? A brief review.

leowest•6mo ago

might be a bit too much to read let me see if there is a simpler version

leowest•6mo ago

ah there we go this one is a bit easier to explain it https://www.tutorialsteacher.com/ioc/dependency-injection

Dependency Injection

leowest•6mo ago

the name is a bit scary but the concept as I explained above is really simple and above that u also have libraries that further implement DI which is a more complex concept

AleOP•6mo ago

it really seems very difficult. Thank you very much I'm already waiting to look over the documentation you sent

MODiX•6mo ago

If you have no further questions, please use /close to mark the forum thread as answered

AleOP•6mo ago

I have another question related to this topic, if I have the form1 class and then I have form2 and I need those parameters in form3, do I do the same? form1 for form3

leowest•6mo ago

yes what is form3

AleOP•6mo ago

another form class where I want to use parameters from formA and among the classes there is the form B class

leowest•6mo ago

Depending on whether u want to access formA method and car, u could instead pass a reference of formA which would give u access to both too so instead of say

    private readonly Car _car;
    public FormB(Car car)
    {
        _car = car;
    }

    private readonly Car _car;
    public FormB(Car car)
    {
        _car = car;
    }

You would do

    private readonly Form1 _parent;
    public FormB(Form1 parent)
    {
        _parent = parent;
    }

    private readonly Form1 _parent;
    public FormB(Form1 parent)
    {
        _parent = parent;
    }

and in Form1 u would have Car as

public Car Car { get; set; }

public Car Car { get; set; }

so u could access _parent.Car.Name or _parent.Class1.Message or some method u made public in Form1 u might also want to use ShowDialog instead of Show so that the user needs to finish interacting with Form2 before it can do any action on Form1 again etc

AleOP•6mo ago

but if I don't need parameters from FormA in Form B, I still can't jump directly to FormC, right?

leowest•6mo ago

what u mean jump to formc? in order to have formc u need to initialize formc and call show from somewhere be it program.cs or forma

AleOP•6mo ago

it is a form that separates the form1 or formA from where I need the values form3 or formC https://paste.ofcode.org/nTgXXEdYTi25vAUwNwpZYD i make an example similar but i add a form class between two forms

leowest•6mo ago

can u like show some images? it might help me provide a better answer

AleOP•6mo ago

leowest•6mo ago

no I mean images of your forms not the code because all this chaining of a to b to c could have been different depending on what they are could have been just like a menu with a panel that replaces usercontrols instead of opening new windows there are many ways to do things

AleOP•6mo ago

from now on I say it's not who knows what

leowest•6mo ago

some make more sense then others as being intuitive so they are like pages to u? u click confirm, it should show the arrow to next?

AleOP•6mo ago

yes

leowest•6mo ago

imagine this then instead of window u create UserControl then u add a panel you do something like

var input = new InputForm();
panel.Add(input);

var input = new InputForm();
panel.Add(input);

u press confirm, now it changes from InputForm to say next page

var next = new NextForm();
panel.Remove(input);
panel.Add(next);

var next = new NextForm();
panel.Remove(input);
panel.Add(next);

this would all be working in a single window as if u were walking pages note: this is just hypothetical code, I have not tested I dont usually use winform, but I know its possible

AleOP•6mo ago

Well, I intentionally put 3 pages because I don't know how to transfer the data from page 1 to page 3 I know that I could do better on one page but I can understand the transfer of data when a page does not need that data and is fixed in the middle. It seems very complicated to me

leowest•6mo ago

u mean this

leowest•6mo ago

I honestly dont understand why u have it

AleOP•6mo ago

yes this is the middle page

leowest•6mo ago

why can't u go from A to C

AleOP•6mo ago

umm idk 😦

leowest•6mo ago

:waaaaaaaaaahhhhhh: it would make more sense no? even if u reverse yoru forms first form having say a label and a button called create car

AleOP•6mo ago

yea i know 70 / 5.000 but I wanted to know how I can do this if there is an extra class in the middle

leowest•6mo ago

and once u create the car on the form2 it returns to form1 and upsate the label with the car name

AleOP•6mo ago

ignore 70/5000

leowest•6mo ago

by extra class you're referring to class Method?

AleOP•6mo ago

I do this thing above because I want to make a project and I made a sketch in my head in which the first form enters some data after the second form does something else and the third form I need data from the first form for a method form2

leowest•6mo ago

well because you're going into a chain i.e.: u open form2 from form1 and form3 from form2 then yes u need to chain passing that reference unless you create a singleton of car which I am not sure I would recommend at this point but if u use, usercontrol as pages and panel then it would be slightly different

AleOP•6mo ago

so it is not done as shown the first time?

leowest•6mo ago

this is sort of what u have right now

AleOP•6mo ago

that's how I want it to work like you did above

leowest•6mo ago

then yes u need to do what I explained earlier that is what I am doing above

AleOP•6mo ago

can you show me the code pleaseeeeeeeeeeeee

leowest•6mo ago

I already have 👆

AleOP•6mo ago

i made this in formA var formB = new FormB(car); formB.Show(); and in form B i put this var formC = new FormC(car); formC.Show();

leowest•6mo ago

yes

leowest•6mo ago

this is what the other way looks like

leowest•6mo ago

without using multiple windows this is using UserControl and a single window the process is similar to what u do with window in terms of passing the car over, but it all exists in a single window and feels more consistent as if u were navigating from page to page

AleOP•6mo ago

and you also put the instance of car here, right?

leowest•6mo ago

no u dont change Form1 only Form2 and 3 Car already exists in Form1

leowest•6mo ago

u can remove the readonly on Form1 leave on the others

AleOP•6mo ago

i dont know what i do but don t show the name of car

leowest•6mo ago

looks fine what I would change is

leowest•6mo ago

dont do this u assign textBoxNameCar.Text to _car.NameCar before testing if textBoxNameCar.Text is safe to use

if (string.IsNullOrEmpty(textBoxNameCar.Text))
{
    label2.Text = "Car name cannot be empty";
    return;
}

if (textBoxNameCar.Text.Length < 3)
{
    label2.Text = "Car name must contain more than 3 letters";
    return;
}

_car.NameCar = textBoxNameCar.Text;

if (string.IsNullOrEmpty(textBoxNameCar.Text))
{
    label2.Text = "Car name cannot be empty";
    return;
}

if (textBoxNameCar.Text.Length < 3)
{
    label2.Text = "Car name must contain more than 3 letters";
    return;
}

_car.NameCar = textBoxNameCar.Text;

AleOP•6mo ago

don t appear the name of car

leowest•6mo ago

can you show me the Car class

AleOP•6mo ago

when i press the button show name

AleOP•6mo ago

leowest•6mo ago

yes I understand that, I am trying to help u by fixing the things I see that are wrong such as the ones I pointed above

MODiX•6mo ago

leowest

can you show me the Car class

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AleOP•6mo ago

leowest•6mo ago

ok looks fine... u forgot to

AleOP•6mo ago

leowest•6mo ago

VerNameCar is not being called so it never sets the car name when u hit confirm :catderp:

AleOP•6mo ago

damn i forgot :Smadge:

leowest•6mo ago

:waaaaaaaaaahhhhhh: anyway I will be back in 20 minutes need to leave my seat

AleOP•6mo ago

it worked, thank you very much for everything :catHeyHello:

leowest•6mo ago

np 😉

MODiX•6mo ago

If you have no further questions, please use /close to mark the forum thread as answered

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Acces data from another form