connecting database with application

i think this example help you :-

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Data;
using System.IO;
namespace abc
{
    class clsDeclerson
    {
        
        public static SqlConnection cn = new SqlConnection();
        
        public static void connectionOpen()
              {
                   cn.ConnectionString = "Data Source=" + server name+ ";Initial Catalog=SMS;User ID=" + server user Name+ ";Password=" + SQLPassword + "";

                   if (cn.State == ConnectionState.Closed) { cn.Open(); }
               }
        public static void insertUpdateDelete()
               {
                   SqlCommand comd = new SqlCommand("insert into abc(id,name) values(1,rr)",cn);
                
                   comd.ExecuteNonQuery();

                   SqlCommand comdU = new SqlCommand("update abc set=name=rr where id=1",cn);
                
                  comdU.ExecuteNonQuery();

                  SqlCommand comdD = new SqlCommand("delete abc where id=1",cn);
                
                  comdD.ExecuteNonQuery();


               }
            }
}

try this link
about button "add,delete,update,cancel,insert,clear" events windows application[^]

Simple example to start with,

Connecting To Sql Server 2008 Sample Database[^]

Hope it helps.

Its better to make an global class which consisting code for opening Gloabal Connection as well as DML operation

public static SqlConnection GetConnection()
      {
          SqlConnection con = new SqlConnection("Your Connection String");
          con.Open();
          return con;
      }

or create an global function for Save,Update and Delete

public static bool SaveRecord(string query)
        {
            int i = 0;
              cmd = new SqlCommand(query, GetConnection());
              try
              {
                  i = cmd.ExecuteNonQuery();
              }
              catch (Exception ex)
              {
                  Console.WriteLine(ex.Message.ToString());
              }
                if (i == 1)
                {
                    return true;
                }
                else
                {
                    return false;
                }
        }

How to using SaveRecord(string query) Function

Just passed query to SaveFunction(string query) method as a parameter and hold value in a boolean.
Ex:-

bool res = SaveRecord("Your Command");
if(res)
{
//Saved
}