Prime Calculator

form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Trying_Something_New
{
    public partial class Form1 : Form
    {
        List<int> _divisors = new List<int>();

        public Form1()
        {
            InitializeComponent();
            //lbDivisors.DataSource = _divisors;
        }

        private void btnCheckNumber_Click(object sender, EventArgs e)
        {
            string stringNumber = tbNumber.Text;

            if(lblResult.Text != "")
            {
                MessageBox.Show("Already displaying results.");
            }

            else if(stringNumber == "1" || stringNumber == "0")
            {
                MessageBox.Show("Value must be larger than 1.");
                tbNumber.Clear();
            }
            else if(tbNumber.Text == "")
            {
                MessageBox.Show("Key-in an integer.");
            }
            else if(stringNumber.Contains("."))
            {
                MessageBox.Show("Value must be an integer.");
                tbNumber.Clear();
            }
            else
            {
                int number = int.Parse(stringNumber);
                int absNumber = Math.Abs(number);
                _divisors.Clear();

                for (int i = 1; i <= absNumber; i++)
                {
                    int remainder;
                    int dividend = absNumber;

                    remainder = dividend % i;

                    if (remainder == 0)
                    {
                        _divisors.Add(i);
                    }
                }

                if (_divisors.Count > 2)
                {
                    //List<int> range = _divisors.GetRange(1, (absNumber - 1));
                    int last = _divisors[_divisors.Count - 2];
                    _divisors.RemoveAt(0);
                    _divisors.Remove(absNumber);
                    lblResult.Text = "This number IS NOT prime.";
                    lblNumberOfDivisors.Text = _divisors.Count.ToString();
                    lblLargest.Text = last.ToString();
                    //lbDivisors.Items.Add(_divisors.ToString());
                    lbDivisors.Items.Add
                }
                else if (_divisors.Count < 2)
                {
                    MessageBox.Show("Something isn't quite right here.  Figure it out asshole.");
                }
                else
                {
                    lblResult.Text = "This number IS prime.";
                }
            }
        }

        private void tbNumber_MouseClick(object sender, MouseEventArgs e)
        {
            
            lblResult.Text = "";
            tbNumber.Clear();
            lblNumberOfDivisors.Text = "";
            lblLargest.Text = "";
            lbDivisors.Items.Clear();
        }
    }
}