Inserting List items to database

using System.Collections.Generic;
using System.Data.SqlClient;



class Program
{
    static void Main(string[] args)
    {
        List<Entity> list = new List<Entity>();
        list.Add(new Entity() { ID = 1, Name = "karthik", Address = "Bangalore" });
        list.Add(new Entity() { ID = 1, Name = "Parthip", Address = "Ahmdabad" });
        list.Add(new Entity() { ID = 1, Name = "Krishna", Address = "Delhi" });
        string conn = @"Data Source=.;Initial Catalog=databasename;Integrated Security=True;";
        foreach (Entity item in list)
        {
            SqlCommand sqlCmd = new SqlCommand();
            SqlConnection objConn = new SqlConnection();
            objConn.ConnectionString = conn;
            objConn.Open();
            sqlCmd.Connection = objConn;
            sqlCmd.CommandTimeout = 30;
            string values = string.Format("({0},'{1}','{2}')", item.ID, item.Name, item.Address);
            // for string datatypes u have to use '{}'  , for number datatype use {}
            sqlCmd.CommandText = "insert into tablename (ID,Name,Address,Column1,Column2....) values  " + values;
            sqlCmd.ExecuteNonQuery();
        }
    }
    class Entity
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public string Address { get; set; }

    }
}