ASP.Net Error: ExecuteReader requires an open and available Connection

i have to upload a sheet into my database but the sheet names differ, i have seen an example on how to upload when sheet name is unknown, i see the sheet names are being found when i look at the complie but before it gets to bulkcopy into my database i get the error 'ExecuteReader requires an open and available Connection error' but my connection is open.

heres the code:

public void up(string sFileName = @"filename")
{
    string ssqltable = "[dbo].[April]";
    try
    {
        string sConStr = string.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties='Excel 8.0;HDR=YES';", sFileName);
        DataTable dt = new DataTable();
        SqlConnection sqlconn = new SqlConnection(strConnString);
        sqlconn.Open();
        using (OleDbConnection connection = new OleDbConnection(sConStr))
        {
            connection.Open();
            dt = connection.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, new object[] { null, null, null, "TABLE" });
            var sheets = dt.Rows[0].Field<string>("TABLE_NAME");
            foreach (var sheet in sheets) //loop through the collection of sheets ;)
            {
                //your logic here...
                string myexceldataquery = string.Format("Select * FROM [{0}]; ", sheets);
                //get data
                OleDbCommand oledbcmd = new OleDbCommand(myexceldataquery, connection);
                OleDbDataReader dr = oledbcmd.ExecuteReader();
                {
                    //sql bulk copy here!
                    DataTable table = new DataTable("benlist");
                    table.Load(dr);
                    // add two extra columns to data table to be added to database table [UPLOAD]
                    table.Columns.Add("Filename", typeof(string));
                    table.Columns.Add("User", typeof(string));
                    //set path
                    string CurrentFilePath = Path.GetFullPath(fuAttachment.PostedFile.FileName);
                    // add data to additional columns
                    foreach (DataRow row in table.Rows)
                    {
                        row["Filename"] = Path.GetFileNameWithoutExtension(CurrentFilePath);
                        row["User"] = Session["Username"].ToString();
                    }
                    Session["filename"] = Path.GetFileNameWithoutExtension(CurrentFilePath);
                    SqlBulkCopy bulkcopy = new SqlBulkCopy(strConnString);
                    bulkcopy.DestinationTableName = ssqltable;
                    ////Mapping Table column
                    bulkcopy.ColumnMappings.Add("ParentId", "[ParentId]");
                    bulkcopy.ColumnMappings.Add("Date", "[Date]");
                    bulkcopy.ColumnMappings.Add("Caption", "[Caption]");
                    bulkcopy.ColumnMappings.Add("Filename", "Filename");
                    bulkcopy.ColumnMappings.Add("User", "User");
                    bulkcopy.WriteToServer(table);
                    connection.Close();
                    sqlconn.Close();
                }
            }           
        }
    }
    catch (Exception) { }
    ClientScript.RegisterStartupScript(GetType(), "alert", "alert('File Uploaded');", true);
}