Passing data to a non-static listBox, by calling function from another class

I have a simple forms program that I have been fighting with for a while now. I simply want to be able to call a method from a different class file (when a certain step is triggered in the code in that class file) in order to insert a string in the listBox.

Here is my main method, pretty standard:

class Program
{
    [STAThread]
    static void Main(string[] args)
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new MainForm());
    }
}

Here is the function which resides in my MainForm.cs file, which I can call just 开发者_StackOverflowfine from that class file (via 'TextToBox(myString);'):

public partial class MainForm : Form
{
    ...
    // Function to output results to main Listbox window        
    public void TextToBox(string aString)
    {            
        // Place messages in Main Display list box window
        this.listBox1.Items.Insert(0, aString);            
    }
    ...
}

But my problem is when I am in another class and I want to call 'TextToBox(myString);'. If I create another object reference of the MainForm, the code compiles fine but nothing will show up in the listBox. How do I do this? I cannot simply make TextToBox() static. I know I must create the object reference but I can't figure out how to reference the ORIGINAL MainForm, the one that was created in the Main method. Thanks in advance...

This will work, but only when you have one instans of MainForm.

public class MainForm : Form
{
    public MainForm()
    {
        Instance = this;
    }

    public static MainForm Instance { get; private set; }

    // Function to output results to main Listbox window        
    public void TextToBox(string aString)
    {
        // Place messages in Main Display list box window
        this.listBox1.Items.Insert(0, aString);
    }

}
public class Other
{
    public void AddTextToListBox()
    {
        MainForm.Instance.TextToBox("Test");
    }
}

...Edit... Alternative:

class Program
{
    public static MainForm MainFormInstance;
    [STAThread]
    static void Main(string[] args)
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        MainFormInstance = new MainForm();
        Application.Run(MainFormInstance);
    }
}

public class Other
{
    public void AddTextToListBox()
    {
        Program.MainFormInstance.TextToBox("Test");
    }
}

I would just pass a delegate to the other class.

/* this runs (previous code was not guaranteed to run) */
class OtherClass
{
    public delegate void TextToBox(string s);

    TextToBox textToBox;
    int next = 0;

    public OtherClass(TextToBox ttb)
    {
        textToBox = ttb;
    }

    public void SendSomeText()
    {
        textToBox(next.ToString());
        next++;
    }
}

I'm assuming you'll be instantiating OtherClass from MainForm. Is this how you're calling "OtherClass"?

public partial class MainForm : Form
{
    OtherClass otherClass;

    public MainForm()
    {
        /* just two controls -- listBox1 and button1 */
        InitializeComponent();
        otherClass = new OtherClass(this.TextToBox);
    }

    public void TextToBox(string aString)
    {
        listBox1.Items.Add(aString);
    }

    private void button1_Click(object sender, EventArgs e)
    {
        otherClass.SendSomeText();
    }
}

On a button click the next numeric value is added at the beginning of the ListBox. You'll have to post some of your code if you need further help.

alternatively you could use a singleton pattern, or static methods and make sure you include the class in a 'using' statement at the top of your program