Get Value From SQL Server 2005 Select Statement With Datareader

I just want a simple datareader, that i can read the value returned from a select statement executed on a SQL server 2005 db.
 The code below should work in, but email[calc]= rdr[0].ToString(); when i want to read some data a get a exception saying:
System.InvalidOperationException was unhandled by user code
  Message="Invalid attempt to read when no data is present."
  Source="System.Data"
  StackTrace:
       at System.Data.SqlClient.SqlDataReader.GetValue(Int32 i)
       at System.Data.SqlClient.SqlDataReader.get_Item(Int32 i)
       at _Default.Login_Click(Object sender, EventArgs e) in d:My DocumentsVisual Studio 2005WebSitesWebSite1Default.aspx.cs:line 47
       at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
       at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
       at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
       at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
       at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
       at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

 If anybody could  advise me where my stupid mistake is then i would highly
appreciate it!


 
        SqlConnection conn = new SqlConnection(getConnection());
        SqlDataReader rdr = null;

        SqlCommand cmd = new SqlCommand();

        cmd.CommandText = "SELECT * FROM Customer";
        cmd.CommandType = CommandType.Text;
        cmd.Connection = conn;

        try
        {
            conn.Open();
               
            rdr = cmd.ExecuteReader();
            
            int calc = 0;

            Boolean login = false;
            string[] email = new string[100];
            object[] password = new object[100];

            while (rdr.HasRows) // or rdr.Read();
            {
                rdr.Read();
                email[calc]= rdr[0].ToString();
                password[calc] = rdr["Password"].ToString();
                if (UserName.Text.Equals(email[calc]) && Password.Text.Equals(password[calc]))
                {
                    login = true;
                }
                calc++;
            }
        }
        finally
        {
            rdr.Close();
        }
 
 
thanks....