I am not able to find the namespace in intelliSense on aspx.cs page

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C#

ASP.NET

Hello I have created below namespace in Connection.cs class.

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

namespace conn
{
public class Connection
{
public SqlConnection con;
public SqlCommand cmd;
//public SqlDataAdapter adt;

string StrError;

public Connection()
{
try
{
con = new SqlConnection(ConfigurationManager.ConnectionStrings["PortfolioMgt"].ConnectionString);
}
catch (SqlException sqlEx)
{
StrError = sqlEx.Message;
}
catch (Exception ex)
{
StrError = ex.Message;
}
}

public void Open_Connection()
{
try
{
con.Open();
}
catch (SqlException sqlEx)
{
StrError = sqlEx.Message;
}
catch (Exception ex)
{
StrError = ex.Message;
}
}
public void Close_Connection()
{
try
{
con.Close();
}
catch (SqlException sqlEx)
{
StrError = sqlEx.Message;
}
catch (Exception ex)
{
StrError = ex.Message;
}
}
}
}


I wanted to use a customized namespace(conn) on Login.aspx.cs page. The code for Login page is as below:

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

public partial class Login : System.Web.UI.Page
{
    Connection con = new Connection();
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void btnLogin_Click(object sender, EventArgs e)
    {
        int investorId;
        investorId=con.select_Inv_Login(txtUserName.Text, txtPassword.Text);

        if(investorId!=0)
        {
            Session["inv_id"] = investorId;
            Response.Redirect("~/MyProfile.aspx");
        }
        else
        {
            lblMsg.Visible = true;
            lblMsg.Text = "User Name or Password incorrect";
        }
    }
}



Once I try to write 'using conn;' it gave me below error:
The type or namespace name 'conn' could not be found (are you missing a using directive or an assembly reference?)