c sharp programming

// BY THE SPIRIT THE CREATOR OF THE WHOLE WORLD
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 System.Data.SqlClient;

namespace testingFormuneDB
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        SqlConnection sqconnection;
        SqlCommand sqlcommand;
        string connectionstring = @"Data Source=.\SQLEXPRESS;AttachDbFilename=c:\users\abayomi\documents\visual studio 2010\Projects\testingFormuneDB\testingFormuneDB\testingMUNEProjDB.mdf;Integrated Security=True;User Instance=True";
        bool flag = false;
        private void btnsubmit_Click(object sender, EventArgs e)
        {

          bool resp=  saveTotalbalance();
          MessageBox.Show(resp.ToString());
        }
        public bool saveTotalbalance()
        {
            int mandatory = int.Parse(txtboxmandatory.Text);
            int voluntary = int.Parse(txtboxvoluntary.Text);
            int prevoiusbalance = int.Parse(txtboxpreviousbalance.Text);

            int totalbalance = mandatory + voluntary + prevoiusbalance;
            txtboxtotalbalance.Text = totalbalance.ToString();
                    
            sqconnection = new SqlConnection(connectionstring);
            sqconnection.Open();
            string commanntxt = "insert into repaymentTB (totalbalance) values('" + totalbalance + "') ";

            sqlcommand = new SqlCommand(commanntxt, sqconnection);
            sqlcommand.ExecuteNonQuery();
            flag = true;
            return flag;

        }
        public void retrivebalance()
        {
            sqconnection = new SqlConnection(connectionstring);
            sqconnection.Open();
            string commandtxt = "select totalbalance from repaymentTB ";
            sqlcommand = new SqlCommand(commandtxt, sqconnection);

            DataTable dt = new DataTable();
            DataSet ds = new DataSet();
            SqlDataAdapter sqldatadapter = new SqlDataAdapter(sqlcommand);
            sqldatadapter.Fill(ds);
            dt = ds.Tables[0];
            foreach (DataRow r in dt.Rows)
            {
                lblpreviousbalance.Text = r["totalbalance"].ToString();
            }
          
            sqconnection.Close();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            retrivebalance();
        }
       
    }
}