How can I share variables or properties between classes?

Question

Is there a way to share variables or properties between two classes?

For example, I have a Blazor web app with 2 pages and 2 partial classes. How can I share the variable A from class 1 with class 2?

Is there a way to do this?

I would be very grateful for an answer.

Members of every class are stored in memory. When you access member of Class1, this is different location from any member in Class2. Do you want something like *friend function* in C++? There is already question about this: [equivalent of friend](https://stackoverflow.com/questions/204739/what-is-the-c-sharp-equivalent-of-friend) — Lazar Đorđević, Mar 17 '22 at 21:18

score 3 · Answer 1 · edited Mar 18 '22 at 01:59

3

You could transfer the property through the parameter of the constructor. So for instance you are in Form1 and want to transfer variable_A to Form2 then you simply put variable_A in the constructor of Form2.

The code in Form1:

 private void GoToSecondForm_Click(object sender,eventarg e)
 {
   Form2 f = new Form2(variable_A);
   this.Hide();
   f.ShowDialog();
 }

Code in the constructor of Form2:

 {dataType} variable_A;
 public Form2({dataType} variable_A)
 {
   InitailizedComponent();
   this.variable_A = variable_A;
 }

If you do this then you will be able to use a variable in another form.

edited Mar 18 '22 at 01:59

Jeremy Caney

7,102
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answered Mar 17 '22 at 21:05

afedjah

162
3

Mmm, giving a "how we might do it in winforms" answer to a Blazor question might not be too helpful.. – Caius Jard Mar 21 '22 at 12:42

score 1 · Answer 2 · edited Mar 18 '22 at 00:32

If you have a class with a member variable that you want to be accessed in another class, you will want to include accessor/mutator (getter/setter) methods in the first class. For example, if you had two classes A and B, and A had a variable x that you wanted to access, you would do something like this:

public class A {
  private int _x = 0;

  public int getX() {
    return this._x;
  }
  public void setX(int x) {
    this._x = x;
  }
}


public class B {
  A a = new A();

  public int returnX() {
    a.setX(8);
    return a.getX();
  }
}

The returnX function would return 8 in this case. If we didn't set _x to 8, it would return 0, as that is what _x is initialized to when new A() is called. You can make _x a public variable and access it by writing something like a._x in B, but this is generally considered bad practice.

score 1 · Answer 3 · answered Mar 18 '22 at 16:49

I'm making an assumption that by "Classes" you mean "Blazor Components".

If so, a simple way is via a Scoped Data Service through Dependency Injection.

Your Service:

    public class MyDataService
    {
        public int MyInt { get; set; }
    }

Add to the Services container in Program:

builder.Services.AddSingleton<WeatherForecastService>();
// The service
builder.Services.AddScoped<MyDataService>();

Any Component/Page can set or consume it.

@page "/"
@inject MyDataService DataService
<PageTitle>Index</PageTitle>

<h1>Hello, world!</h1>

Welcome to your new app.

<SurveyPrompt Title="How is Blazor working for you?" />

@code {
    private int myInt = 0;
    protected override void OnInitialized()
    {
        this.DataService.MyInt = 2;
        //...
        myInt = this.DataService.MyInt;
    }
}

How can I share variables or properties between classes?

3 Answers3