Declaring Main as Static Throws Errors [closed]

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On my last compile, I received the following build errors:

"An object reference is required for the non-static field, method, or property ..."

and then a list of all of the items contained inside of my Main().

Previously, it read static Main() {, but I could not get the errors to go away until I changed this to public Main() {.

I don't recall the last thing I did before this started occurring (this was late last night), but I do believe I was messing with the static void recalcTotals() trying to reference field items on the main form - to which I still have not figured it out, but that is a seperate issue.

Mind you, this is my first C# program. Below is basically my code:

namespace Play_XXX
{
    public partial class Main : Form 
    {
        // Enable moveability
        private const int WM_NCHITTEST = 0x84;
        private const int HTCLIENT = 0x1;
        private const int HTCAPTION = 0x2;

        // Handling the window messages
        protected override void WndProc(ref Message message) {
            base.WndProc(ref message);

            if (message.Msg == WM_NCHITTEST && (int)message.Result == HTCLIENT)
                message.Result = (IntPtr)HTCAPTION;
        }

        public Main() {
            InitializeComponent();

            // Handle all auto-formatting textboxes
            txt1.Leave += new EventHandler(validateInput);
            txt2.Leave += new EventHandler(validateInput);
            txt3.Leave += new EventHandler(validateInput);
            txt4.Leave += new EventHandler(validateInput);
            txt5.Leave += new EventHandler(validateInput);
            txt6.Leave += new EventHandler(validateInput);
            txt7.Leave += new EventHandler(validateInput);
            txt8.Leave += new EventHandler(validateInput);
            txt9.Leave += new EventHandler(validateInput);
            txt10.Leave += new EventHandler(validateInput);
            txt11.Leave += new EventHandler(validateInput);
        }

        private void Main_Load(object sender, EventArgs e) {
            //TODO: Reference function to clear all input forms
        }

        static decimal? trueAmount(string testValue) {
            decimal preOut;

            //TODO: RegEx to remove all except digits?
            if (testValue != null && testValue != "")
                testValue = testValue.Replace(",", "").Replace("$", "");
            else
                testValue = "0";

            //Return value
            if (decimal.TryParse(testValue, out preOut))
                return preOut;
            else
                return null;
        }

        void validateInput(object sender, EventArgs e) {
            TextBox subjBox = (sender as TextBox);

            decimal? trueVal = trueAmount(subjBox.Text);

            //Check if this is a number
            if (trueVal.HasValue) {
                subjBox.Text = trueVal.Value.ToString("C");
                subjBox.BackColor = Color.FromArgb(86, 86, 86);
                subjBox.ForeColor = Color.FromArgb(208, 210, 211);
                recalcTotals();
            }
            else {
                subjBox.BackColor = Color.FromArgb(255, 200, 200);
                subjBox.ForeColor = Color.Maroon;
            }
        }

        static void recalcTotals() {
            //TODO: How the fxck do your reference form controls
        }

        private void btnClose_Click(object sender, EventArgs e) {
            Close();
        }

    }
}

Answer 1

Name your class everything other than Main (e.g. MainForm).

Answer 2

Note that a constructor looks different than a method.

A method has a name that is different from the class name, and it has a return type such as void or int. These are methods:

class C
{
  public void M1()
  {
  }
  public static void M2()
  {
  }
  public int M3()
  {
    return 10;
  }
  public static int M4()
  {
    return -10;
  }
}

Constructors must have the same name as the class and must not have a return type. These are constructors:

class C
{
  public C()
  {
  }
  static C()
  {
  }
}

Constructors are typically used to set up "state" before the class is used.

An entry point is a special method of which there can be only one in a program. The entry point must be a method, it must be static and it must be named Main. It follows that the entry point cannot be a direct member of a class that is also called Main.

I don't think it is usual to have the entry point inside the class that derives from Form, in a Windows Form application, but it should certainly be possible when the naming respects the above.

Furthermore, a non-static constructor or method can access all members of the class directly. When another non-static member is referred like that, the same instance of the class as the method/constructor belongs to (called this) is implicitly used to access the other member.

In contrast, a static constructor or method can only access a non-static member by explicitly having an instance, as in myInstance.TheNonStaticMember();. Typically, the entry point, which is a static method as I said, will create an instance with new TheClassName(...).