Making a class in C# ASP.net for SQL univarsal connection

class name : Connection.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient; //for sql data connection;
using System.Data;  // for data set data table ;
using System.Windows.Forms; // for taking a refrence of controls in a class file. like combobox;

//this class is make for universal sql connnection in the project;
namespace WFA2
{
    class Connection
    {
        public static SqlConnection conn()
        {
            SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=Northwind;User ID=sa");
            return con;
        }
        public static DataSet getData(String str)  // this connection architecture .... no need to open connection // to display data
        {
          
                SqlConnection con = Connection.conn();
                SqlDataAdapter da = new SqlDataAdapter(str, con);
                DataSet ds = new DataSet();
                da.Fill(ds);
                return ds;
        }
        public static void AllPer(String str)  // this is not this connection architecture // to inserting data
        {
            SqlConnection con = Connection.conn();
            SqlCommand cmd = new SqlCommand(str,con);
            con.Open();
            cmd.ExecuteNonQuery();
            con.Close();
        }
    }
}


Using class for accessing connection

// this will show the data from table in grid viewer
private void button1_Click(object sender, EventArgs e)
        {
            DataSet ds = Connection.getData("Select * from infoCustomer");
            dataGridView1.DataSource = ds.Tables[0];
        }

Note : Take a button named it button1 and take a dataGridView1 control from toolbox;

// this will insert the data in table

private void button2_Click(object sender, EventArgs e)
        {
            Connection.AllPer("insert into infoCustomer values('" + comboBox1.Text + "','"+txtAge .Text +"','"+txtSalary .Text+"')");
            MessageBox.Show("Record Inserted");
        }



Adding the items from data table into combobox on run time


Make a class for FillBox method

public static void FillBox(ref ComboBox cmb, string str) //using System.Windows.Forms; here
        {
            DataSet ds = Connection.getData(str);
            for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
            {
                cmb.Items.Add(ds.Tables[0].Rows[i].ItemArray[0].ToString());
            }
        }


On Form Load Code
private void Form1_Load(object sender, EventArgs e)
        {
            Connection.FillBox(ref comboBox1, "select name from infoCustomer");
        }

Note: "Connection.FillBox " is used regarding to Connection.cs class file...you can change the word "Connection" if your class file name is different.