a check condition for my C# windows form application

[donofwar5]

i am new to C#. i need to create a windows form application for adding 5 student record using array... i have created it but i want to put a check condition for student id that is if it get repeted then a message should be displayed "student id all ready exist". but when i enter the detail of 1st student then that message is displayed....

here is the code that i have written:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using old_class_to_be_mod;
 
namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
       // int[] arr = new int[3];
      // Student s = new Student();
        Student[] s = new Student[5];
 
        private void Form1_Load(object sender, EventArgs e)
        {
            label1.Text = "Id";
            label2.Text = "Name";
            label4.Text = "Marks of Sub 1";
            label5.Text = "Marks of Sub 2";
            label6.Text = "Marks of Sub 3";
            label7.Text = "Marks of Sub 4";
            label8.Text = "percentage";
 
        }
        int i = 0;
        private void button1_Click(object sender, EventArgs e)
        {
 
 
            s[i] = new Student();
            s[i].ID = int.Parse(textBox1.Text);
            s[i].Name = textBox2.Text;
            s[i].SEM = int.Parse(textBox3.Text);
            s[i].get_marks(double.Parse(textBox4.Text), double.Parse(textBox5.Text),
                double.Parse(textBox6.Text), double.Parse(textBox7.Text));
            textBox8.Text = s[i].ret_per().ToString();
            if (check() == false)
            { MessageBox.Show("User allready Exist"); }
            i++;
 
        }
 
        bool check()
        {
            for (i = 0; i < s.Length; i++)
            {
                if(s[i].ID==int.Parse(textBox1.Text))
                {return false;
                break;}
 
 
                }
            return true;
        }
        private void button2_Click(object sender, EventArgs e)
        {
            for (i = 0; i < s.Length; i++)
            {
                richTextBox1.Text += s[i].Name +"->" + s[i].ret_per().ToString()+"\n";
            }
        }
    }
}

[Rabbit]

Please use code tags when posting code or formatted data.

The problem is that you're checking the student against itself. You need to check first before creating the student.