Use class method from another class

Question

Hello there! Iam trying to use a method in class, from another class.

namespace Crystal.Utilities
{
   public class Logging
   {
      public static void Log()
      {
          //dostuff
          Crystal.MainForm.general_log_add_item("Hello World");
      }
   }
}

namespace Crystal
{
   public partial class MainForm : Form
   { 
      public void general_log_add_item(string msg)
      {
         listBox1.Items.Add(msg);
      }
   }
} 

I want to be able to call Crystal.Utilities.Logging.Log() from anywhere, and that to be able to call Crystal.MainForm.general_log_add_item() . But It doesnt let me, becuase if I put it as public, then I cant see it, if its static then It cant interract with my listbox :/

Answer 1

You have to understand that the window is not static, there is one instance of him, thats why the method cant be static, you can use Application.Windows to reach this instance and call the add method.

or you can register the window in his constructor on another class that will mediate the Logging and the window.

If you don't understand tell me and I'll try to be more clear

Answer 2

Instead of implementing it as a static method, try implementing as a singleton. It's a common trick to make an instance global in scope, and restrict to one instance, without making everything static (and thus unable to be used as an instance).

Answer 3

When you declare a method as "static" you're saying that it's not dependent upon a specific instance of the class it's in.
For example if you have a class named "chair" and you want to count how many chairs there are, you'll do that with a static field, and a static method to return that field's value.
The count of all chairs is not related to a specific chair.
In your case you want to add a static method to add an item to a specific instance of a Form. That's impossible and doesn't make sense.
If you want to add an item to a listBox, it must be through a public method.
So basically what I'm saying is - rethink what you're trying to do, there's a good explanation as to why you're not succeeding in doing that.

Answer 4

This is a wrong approach. Your class should not call into the UI, as the UI could change. The class should not know nor care about the UI. Instead, the class could expose an event that the form could subscribe to, and update based upon the information contained within the event's arguments.

Here's a hastily thrown together example.

class Program
{
    static void Main()
    {
        Logger.OnLogging += Logger_OnLogging;
        Logger.Log();
        Logger.OnLogging -= Logger_OnLogging;
    }

    static void Logger_OnLogging(LoggingEventArgs e)
    {
        Trace.WriteLine(e.Message);
    }
}

public class Logger
{
    public delegate void LoggingEventHandler(LoggingEventArgs e);

    public static event LoggingEventHandler OnLogging;

    public static void Log()
    {
        // do stuff
        RaiseLoggingEvent("Data logged");
    }

    protected static void RaiseLoggingEvent(string message)
    {
        if (OnLogging != null)
            OnLogging(new LoggingEventArgs(message));
    }
}

public class LoggingEventArgs : EventArgs
{
    public LoggingEventArgs(string message)
    {
        this.Message = message;
    }

    public string Message { get; private set; }
}