How can I access my method from another class-CodePudding

I'm very new to c#, I started a few days ago, so please excuse me if it is basic. I have two forms, the first one is like a login page, where someone enters their name. On my "Info.cs" class, it reads this name via a setter, into a variable, and my Getter called "GetCardName" returns this Name. I now made a new form where I want to access this name via the GetCardName getter, just dont know how too. Heres the code :

Here is some of the "info.cs" class code:

private string CardName { get; set; } = "";
   
public string GetCardName()
{
    return this.CardName;
}

public void SetName(string name = "")
{
    this.CardName = name;
}

And here is the code from the other form that is just trying to call GetCardName():

private void Form2_Load(object sender, EventArgs e)
{
    lblWelcome.Text = Info.GetCardName();
}

CodePudding user response：

When creating Form2 you need also pass it reference to the other form to get its properties.

So when creating and showing Form1 you should also create Form2 to pass that reference. Example (not tested) code:

var form1 = new Form1();
var form2 = new Form2(form1);
form1.Show();

and Form2 should be like:

public class Form2
{
    private Form1 _form1;

    public Form2(Form1 form1)
    {
        _form1 = form1;
        // ... other initialization code
    }
    
    // ... other class declarations
}

General solution is: you need to persist reference to the Form1 being shown to the user and then pass that reference to Form2 whenever you create it.

CodePudding user response：

You have two options :

you can create an instance of the class that you want to call EX : Info infoVar = new Info(); (now you can use infoVar to call any methods of the Info.cs class)
you can make Info class a STATIC class (probably not what you want to do, but still helpful for the future perhaps) This makes it possible to call the info class directly without having to create a variable of that class but has some drawbacks. (more info here)

CodePudding user response：

There is few ways to achieve what you want:

Public static property:

public class Info
{
    public static string CardName { get; set; } = string.Empty;
}

You can access it or set value to it directly by:

private void Form2_Load(object sender, EventArgs e)
{
    // Set
    Info.CardName = "Some name"; 
    // Get
    lblWelcome.Text = Info.CardName;
}

Public non-static property:

public class Info
{
    public string CardName { get; set; } = string.Empty;
}

You can access it or set value to it directly too, but need to create Info class instance before:

private void Form2_Load(object sender, EventArgs e)
{
    Info info = new Info();
    // Set
    info.CardName = "Some name"; 
    // Get
    lblWelcome.Text = info.CardName;
}

Private static field with separated public static Get and Set methods:

public class Info
{
    private static string cardName = string.Empty;

    public static string GetCardName()
    {
        return cardName;
    }

    public static void SetCardName(string name = "")
    {
        cardName = name;
    }
}

You can access GetCardName and SetCardName without creating Info class instance:

private void Form2_Load(object sender, EventArgs e)
{
    // Set
    Info.SetCardName("Some name"); 
    // Get
    lblWelcome.Text = Info.GetCardName();
}

Private non-static field with separated public non-static Get and Set methods:

public class Info
{
    private string cardName = string.Empty;

    public string GetCardName()
    {
        return cardName;
    }

    public void SetCardName(string name = "")
    {
        cardName = name;
    }
}

You can access GetCardName and SetCardName after creating Info class instance:

private void Form2_Load(object sender, EventArgs e)
{
    Info info = new Info();
    // Set
    info.SetCardName("Some name"); 
    // Get
    lblWelcome.Text = info.GetCardName();
}

Difference between fields and properties was pretty nice explained here: What is the difference between a field and a property?. In short, properties are "wrappers" over fields, which usually are private and you can't access to them directly or modify. It is a part of Member Design Guidelines. Also properties allow to add some validations through property setter to be sure that valid value is stored at cardName field, e.g.:

public class Info
{
    private string cardName = string.Empty;
    public string CardName
    {
        get => cardName;
        set 
        {
            // Check that value you trying to set isn't null
            if (value != null)
                cardName = value;
            // Or check that name is not too short
            if (value.Length >= 3) // Card name should be at least of 3 characters
                cardName = value;              
        }
    }    
}