The type or namespace name 'connection' could not be found (are you missing a using directive or an assembly reference?)

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C#

ASP.NET

I have a connection class named "connection" in app-code folder and I called it in aspx.cs file like

connection c=new connection();

It works fine on local host but when I upload all files then it throw error "The type or namespace name 'connection' could not be found (are you missing a using directive or an assembly reference?)"
How can i fix this?
my connection file code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.SqlClient;
using System.Data;
using System.Web.UI.WebControls;
using System.Configuration;


/// <summary>
/// Summary description for connection
/// </summary>
public class connection
{
    public SqlConnection con = new SqlConnection();
    public SqlCommand cmd = new SqlCommand();
    public SqlDataAdapter adp = new SqlDataAdapter();
    public DataSet ds = new DataSet();
    public DataRow dr;
    public SqlCommandBuilder scb;
	public connection()
	{
        con.ConnectionString = ConfigurationManager.ConnectionStrings["email"].ConnectionString;
        adp.SelectCommand = cmd;
        cmd.Connection = con;
		//
		// TODO: Add constructor logic here
		//
	}
    public void ddlbind(string query, string text, string value, DropDownList id)
    {

        ds.Clear();
        cmd.CommandText = query;
        adp.Fill(ds, "vt");
        id.DataSource = ds.Tables["vt"];
        id.DataTextField = text;
        id.DataValueField = value;
        id.DataBind();
        id.Items.Insert(0, "--Select--");
    }
    public void gridbind(GridView id, string query)
    {
        ds.Clear();
        cmd.CommandText = query;
        adp.Fill(ds, "vt");
        id.DataSource = ds.Tables["vt"];
        id.DataBind();
    }
    public void databind(DataList id, string query)
    {
        ds.Clear();
        cmd.CommandText = query;
        adp.Fill(ds, "vt");
        id.DataSource = ds.Tables["vt"];
        id.DataBind();
    }
    public void detailsbind(DetailsView id, string query)
    {
        ds.Clear();
        cmd.CommandText = query;
        adp.Fill(ds, "vt");
        id.DataSource = ds.Tables["vt"];
        id.DataBind();
    }
    public void listbind(ListView id, string query)
    {
        ds.Clear();
        cmd.CommandText = query;
        adp.Fill(ds, "vt");
        id.DataSource = ds.Tables["vt"];
        id.DataBind();
    }
}

and .aspx page code is-

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Net.Mail;

public partial class bulkemail : System.Web.UI.Page
{
    connection c = new connection();
    public string server1 = "gmail.com", user_id = "avatys99@gmail.com", pass = "9198430645";
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            try
            {
                c.cmd.CommandText = "SELECT * FROM SYS.TABLES";
                c.adp.Fill(c.ds, "dk");
                DropDownList1.DataSource = c.ds.Tables["dk"];
                DropDownList1.DataTextField = c.ds.Tables["dk"].Columns["name"].ToString();
                DropDownList1.DataValueField = c.ds.Tables["dk"].Columns["name"].ToString();
                DropDownList1.DataBind();
                DropDownList1.Items.Insert(0, "--Select--");

                c.cmd.CommandText = "select count(*) as dd from excel";
                c.adp.Fill(c.ds, "vt");
            }
            catch (Exception ex)
            {
                Console.WriteLine("{0} Exception caught.", ex);
            }
        }

    }
    protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
    {
        string body = "Name : " + txtsubject.Text + "<br />message : " + txtmsg.Text;
        try
        {
            Label lblname = new Label();
            lblname.Text = DropDownList1.SelectedItem.Text;

            MailMessage Msg = new MailMessage();
            // Sender e-mail address.
            Msg.From = new MailAddress("avatys99@gmail.com");
            // Recipient e-mail address.
            c.cmd.CommandText = "select * from" + " [" + DropDownList1.SelectedItem.Value + "]" + "";
            c.adp.Fill(c.ds, "vt1");
            //string s = c.ds.Tables["vt1"].Rows[i]["elist"].ToString();
            int i = 0;

            int eid = Convert.ToInt32(c.ds.Tables["vt"].Rows[0]["dd"].ToString());
            for (i = 0; i < eid; i++)
            {
                string s = c.ds.Tables["vt1"].Rows[i]["email"].ToString();
                Msg.To.Add(s);
            }

            Msg.To.Add("mishradhiraj66@gmail.com");


            Msg.Subject = txtsubject.Text;
            Msg.IsBodyHtml = true;
            Msg.Body = body;
            // your remote SMTP server IP.
            SmtpClient smtp = new SmtpClient();
            smtp.Host = "smtp.gmail.com";
            smtp.Port = 587;
            smtp.Credentials = new System.Net.NetworkCredential("avatys99@gmail.com", "9198430645");
            smtp.EnableSsl = true;
            smtp.Send(Msg);
            Msg = null;

            txtsubject.Text = "";
            txtmsg.Text = "";
            lblmsg.Text = "Mail send Successfully";
            Page.ClientScript.RegisterStartupScript(this.GetType(), "msg", "<script>alert('Mail send Successfully' )</script>)");
        }
        catch (Exception ex)
        {
            Console.WriteLine("{0} Exception caught.", ex);
            lblmsg.Text = "Mail not Send";
            Page.ClientScript.RegisterStartupScript(this.GetType(), "msg", "<script>alert('Mail not Send' )</script>)");
        }
    }
}