Fudbalski klub i utakmice (combobox)

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

namespace B6_Fudbalski_klub_i_utakmice
{
    public partial class Form2 : Form
    {
        SqlConnection con = new SqlConnection(@"Data Source=DESKTOP-BEDE3AM\SQLEXPRESS;Initial Catalog=B6;Integrated Security=True");
        public Form2()
        {
            InitializeComponent();
        }

        private void Form2_Load(object sender, EventArgs e)
        {
            // TODO: This line of code loads data into the 'b6DataSet.Grad' table. You can move, or remove it, as needed.
            this.gradTableAdapter.Fill(this.b6DataSet.Grad);

            string k = "select top 1 * from Stadion";
            int stadion = 0;
            try
            {
                con.Open();
                SqlCommand cmd = new SqlCommand(k, con);
                SqlDataReader dr = cmd.ExecuteReader();
                while(dr.Read())
                {
                    textBox1.Text = dr[0].ToString();
                    textBox2.Text = dr[1].ToString();
                    textBox3.Text = dr[2].ToString();
                    textBox4.Text = dr[3].ToString();
                    textBox5.Text = dr[4].ToString();
                    stadion = Convert.ToInt32(dr[5].ToString());

                }
                dr.Close();
               // MessageBox.Show(stadion.ToString());


                 string k2 = "select Grad from Grad where GradID="+stadion;
                     SqlCommand cmd2 = new SqlCommand(k2, con);
                     SqlDataReader dr2 = cmd2.ExecuteReader();
                     if(dr2.Read())
                     {
                    comboBox1.SelectedIndex = stadion - 1;
                       }

            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                throw;
            }
            finally
            {
                if (con.State == ConnectionState.Open) con.Close();
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {
            try
            {
                textBox1.Text = "";
                textBox2.Text = "";
                textBox3.Text = "";
                textBox4.Text = "";
                textBox5.Text = "";
                comboBox1.Text = "";
                textBox1.Focus();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                throw;
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {

            string k = "";

            if (textBox1.Text == "")
                k = "select top 1 * from Stadion";
            else
                k = "select top 1 * from Stadion where StadionID=" + (Convert.ToInt32(textBox1.Text)-1);


            try
            {

                con.Open();
                SqlCommand cmd = new SqlCommand(k, con);
                SqlDataReader dr = cmd.ExecuteReader();
                int grad = 0;
                while (dr.Read())
                {
                    textBox1.Text = dr[0].ToString();
                    textBox2.Text = dr[1].ToString();
                    textBox3.Text = dr[2].ToString();
                    textBox4.Text = dr[3].ToString();
                    textBox5.Text = dr[4].ToString();
                    grad = Convert.ToInt32(dr[5].ToString());


                }
                dr.Close();
                string k2 = "";



                    k2 = "select Grad from Grad where GradID=" + grad;
                    SqlCommand cmd2 = new SqlCommand(k2, con);
                    SqlDataReader dr2 = cmd2.ExecuteReader();
                    if (dr2.Read())
                    {
                    comboBox1.SelectedIndex = grad - 1;
                    }

            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                throw;
            }
            finally
            {
                if (con.State == ConnectionState.Open) con.Close();
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            string k = "";

            if (textBox1.Text == "")
                k = "select top 1 * from Stadion  order by StadionID desc";
            else
                k = "select top 1 * from Stadion where StadionID=" + (Convert.ToInt32(textBox1.Text) + 1);


            try
            {

                con.Open();
                SqlCommand cmd = new SqlCommand(k, con);
                SqlDataReader dr = cmd.ExecuteReader();
                int grad = 0;
                while (dr.Read())
                {
                    textBox1.Text = dr[0].ToString();
                    textBox2.Text = dr[1].ToString();
                    textBox3.Text = dr[2].ToString();
                    textBox4.Text = dr[3].ToString();
                    textBox5.Text = dr[4].ToString();
                    grad = Convert.ToInt32(dr[5].ToString());


                }
                dr.Close();
                string k2 = "";



                k2 = "select Grad from Grad where GradID=" + grad;
                SqlCommand cmd2 = new SqlCommand(k2, con);
                SqlDataReader dr2 = cmd2.ExecuteReader();
                if (dr2.Read())
                {
                    comboBox1.SelectedIndex = grad - 1;
                }

            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                throw;
            }
            finally
            {
                if (con.State == ConnectionState.Open) con.Close();
            }
        }

        private void button4_Click(object sender, EventArgs e)
        {
            string k = "insert into Stadion values("+textBox1.Text+ ", N'" + textBox2.Text + "', N'" + textBox3.Text + "', " + textBox4.Text + ", " + textBox5.Text + ", "+comboBox1.SelectedValue+")";
            try
            {
                con.Open();
                SqlCommand cmd = new SqlCommand(k, con);
                cmd.ExecuteNonQuery();
                MessageBox.Show("Uspesno ste uneli stadion");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                //throw;
            }
            finally
            {
                if (con.State == ConnectionState.Open) con.Close();
            }
        }

        private void button5_Click(object sender, EventArgs e)
        {
            this.Close();
        }
    }
}