Question

Hi i am having a problem here. So you can see whenever the txtBtn0 and txtBtn1 is clicked it increments its own array which is then used for squareChecked string. But what I want to do first is to give out an error message if txtBtn0 nor txtBtn1 is not clicked. But it does not pop up anything.

        public partial class MainForm : Form
{
    public int[] clickNumBoxArray = Enumerable.Repeat(1, 81).ToArray();

    public MainForm()
    {
        InitializeComponent();



     }  ... ... ...



        private void btn1_Click(object sender, EventArgs e) {
         UserSquare checkClickedBox = new UserSquare();

        string checkClickBox = checkClickedBox.squareChecked();
        if (checkClickedBox == null) {
        MessageBox.Show("You did not enter any text on the form");
        }
    }

    private void txtBtn1_Click(object sender, EventArgs e) {
        clickNumBoxArray[1]++;
        if (clickNumBoxArray[1] % 2 == 0) {
            txtBtn1.BackColor = System.Drawing.Color.DarkOrange;
        } else {
            txtBtn1.BackColor = System.Drawing.Color.WhiteSmoke;
        }
    }

    private void txtBtn0_Click(object sender, EventArgs e) {
        clickNumBoxArray[0]++;
        if (clickNumBoxArray[0] % 2 == 0) {
            txtBtn0.BackColor = System.Drawing.Color.DarkOrange;
        } else {
            txtBtn0.BackColor = System.Drawing.Color.WhiteSmoke;
        }
    }

This is the other class

     class UserSquare {
    public string squareChecked() {
        string clickedBoxes = null;
        MainForm numBoxArray = new MainForm();
        int[] clickNumBoxArray = numBoxArray.clickNumBoxArray;
         for (int i = 0; i < 81; i++) {
             if (clickNumBoxArray[i] % 2 == 0) {
                 clickedBoxes += "txtBtn" + i + ", ";
             }
         } return clickedBoxes; 
    }

Answer 1

About IndexOutOfRange Exception Your problem is that you implement your list here

public int[] clickNumBoxArray = Enumerable.Repeat(1, 80).ToArray();

as starts from 1 and finished 80 = 80 elements

but in method your for loop starts from 0 and finished 81 = 81 elements

and about controlling by error.. simply and tricky.. you can implement an internal / public boolean as default false and set to true in a mouse event as you need (i.e.mouseclick event)..end of your error method or where you need else, set to back false to be ready for another click-event controlling

About ButtonClick not fire its event (if im not misunderstood) : Did you deleted your some methods of buttons ? could you been forgot to implement it back ?

open your design mode click once onto your controls which you want to check, and then open properties => events.. if your events implemented then it should be as so : (i.e.)

(property) MouseClick (value) Button1_MouseClick