Visual C# Missing partial modifier

I get an error saying "Missing partial modifier on declaration of type 'projectName.Main'; another partial declaration of this type exists. From what i can read about this error, its because i have classes with same name. It does work if i modify the main class to public partial class Main : Form but i want to know why it gives me this error. I need to initializeComponent within Main(), tried creating a method start() and then calling main.Start() in a load event, but then the form loads blank.

namespace projectName
{
    public class Main : Form
    {
        public Main() // Method: Starts the main form
        {
            InitializeComponent();
        }

        public void Main_Load(object sender, EventArgs e)
        // On load of main class, handle events and arguments
        {
            Main main = new Main();
            main.getCurrentDomain();
        }

        public void getCurrentDomain() // Method: Get current domain
        {
            Domain domain = Domain.GetCurrentDomain();
        }
    } // Ends the main class
}