string strConnExcel = "provider=Microsoft.Jet.OLEDB.4.0; data source=" + filename + "; Extended Properties=Excel 8.0;";
    string strSelExcel = "SELECT * FROM [" + sheetname + "]";
            System.Data.OleDb.OleDbConnection ExcelConn;

            ExcelConn = new System.Data.OleDb.OleDbConnection(strConnExcel);

            ExcelConn.Open();

            System.Data.OleDb.OleDbCommand DbCommand = new System.Data.OleDb.OleDbCommand(strSelExcel, ExcelConn);

            System.Data.OleDb.OleDbDataReader DbReader = DbCommand.ExecuteReader();