You can save your data during a HttpRequest by passing it to System.Web.HttpContext.Current.Items[itemKey].
Objects stored in this Collection will be available during the whole lifecycle of the HttpRequest.

Example of usage:

System.Web.HttpContext.Current.Items["reloadCount"] = 5;

int reloadCount = (int) System.Web.HttpContext.Current.Items["reloadCount"];

private DataSet ReadDataSet()
{
   DataSet ds = new DataSet();
   ds.ReadXml(dataPath, XmlReadMode.ReadSchema);
   return ds;
}

private void WriteDataSet(DataSet ds, string path)
{
   ds.WriteXml(path, XmlWriteMode.WriteSchema);
}

public DataSet GetCSVFile( string fileName)
{
     string pathName = System.IO. Path .GetDirectoryName(fileName);
     string file = System.IO. Path .GetFileName(fileName);
     OleDbConnection excelConnection = new OleDbConnection
     (@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+ pathName + ";Extended Properties=Text;");
     OleDbCommandexcelCommand = newOleDbCommand(@"SELECT * FROM "+ file, excelConnection);
     OleDbDataAdapterexcelAdapter = newOleDbDataAdapter(excelCommand);
     excelConnection.Open();
     DataSetds = newDataSet();
     excelAdapter.Fill(ds);
     excelConnection.Close();
     return ds;
}