Using certain variables in different classes (C#)

I'm pretty new to C# and I was trying out a few things. I have a label (named 'newLabel') in the form1.cs. I have a class named 'methods.cs'. In this class I have the method

public static void updateLabel()

what I want to do is:

public static void updateLabel() 
{
    new开发者_StackOverflow中文版Label.Text = "New Value";
}

but this doesn't work, probably because the method is in methods.cs and the newLabel is in form1.cs.

I had the same problem with declared variables. In the methods.cs I had the variable

int value;

but I couldn't use this variable in form1.cs. I fixed this by doing

public static int value { get; set; }

I have no idea what that did but it works, but I don't know how I can apply this trick with the label.

Could someone help me with this?

Thanks!

---

You should read up about OOP and encapsulation. Basically you want the form to access private fields in another object (your class) - this is restricted by encapsulation, that's why you are running into problem - you can get around them by adding those fields and methods to the "public" interface that your class is declaring by making them public properties and methods, i.e in your example:

public int Value {get;set;}

Sometimes composition is used, i.e. in your example since your class is directly accessing the form you could have a form property on your class:

public Form ViewForm {get;set;}

---

It would be best if you learnt C# from tutorials, but the answer to this particular question lies with something called "scope"

Essentially, scope is the visibility of variables, classes, functions and objects. A variable marked "private" can only be seen within the thing that created it (if it's created inside a function it will always be private and any variables defined inside a function can only be used inside that function). If it's created inside a class only that class can use it.

Variables or functions denoted as public (this can only be done inside a class) can be seen from outside that class. To do that you would invoke myClass.myVariable to access the variable or myClass.myFunction() to access the function.

To denote the visibility of an object you use the keywords "public" or "private". Note: This only applies to variables and functions inside classes (it also applies to other things within classes, such as nested classes and structs, but that's outside the scope of this basic intro).

for example:

class myClass
{
    private int myInt;
    public void myfunction()
    {
        myInt = 1;
    }
}

This will work, as myInt can be seen by anything inside myClass

class myOtherClass
{
    private void myfunction()
    {
        myClass myObject = new myClass();
        myObject.myInt = 2;
    }
}

This will not, as myInt is private to myObject and only myObject can change it. myOtherClass does not have permission and it cannot see it.

class myOtherClassTwo
{
    private void myfunction()
    {
        myClass myObject = new myClass();
        myObject.myFunction();
    }
}

This, thankfully, will work. myFunction was set as public in the myClass class, so it can be seen by anybody outside of the class.

Now the keyword static which you use has a whole different meaning. I advise you not to use it until you've learned about it as you're only adding additional complexity to your problems.

I hope this has cleared things up, though I must urge you to follow some real tutorials as these basics must be thoroughly detailed or you'll be caught out later on.

---

Since your updateLabel method accesses the label inside the form, correct object-oriented design would dictate that this method should be in the form, too. Then you have no problem accessing newLabel.

Technically speaking: newLabel doesn’t mean anything outside a form object. You could have several copies of your form, which would mean several copies of your newLabel; which of them should it refer to? Of course the computer won’t take a guess there; it’ll expect that you tell it which form you want to use.

The reason you couldn’t access the value variable is because it was private. If you had changed it simply to:

public static int value;

then it would have worked.

---

From the Form1, call the updateLabel method in the mothods class:

methods updateMethod = new methods();
newLabel.Text = updateMethod.updateLabel();

With this method in the methods class:

public static string updateLabel(){
return "New Value";
}