I’m struggling to understand how to implement principles of encapsulation, inheritance and polymorphism to break this code into logical parts. My background is in VBS/Classic ASP and database development, not OOP.

I’m not asking anyone to write the code, but rather to point me in the right direction. I have this class, which I suppose is something I’ve heard referred to as a God Object.

My code works, but it’s unmanageable and will only get worse.

This class:

1. Receives information about a data source, like the path to an Access database or the name of a db server.
2. Determines which engine can process the file… Access, MSSQL, MySQL…
3. Select a Provider to connect to the DBMS
4. Set db specific settings, like whether to use single or double quotes around object names, etc.
5. Generate a connection string to connect to the db.

Is it Ok to have all this stuff in a single class?

I was thinking it would be easier to understand later, if I separated it into a few different classes:

1. A class to figure out what kind of data source it will connect to
2. A class to set db specific settings and generate a connection string

Does that sound right? If so, would you recommend maybe pulling all of these enums and their accompanying methods into a separate static class so that they don’t need to be instantiated?

using System; using System.Diagnostics; using System.IO;  namespace RickRoll { public class Db {     public string DataSource { get; }     public string Database { get; }     public string Username { get; }     public string Password { get; }     public string ConnectionString { get; private set; }     public string ExtendedProperties { get; }      private WrapColumn wrapcol;     private WrapObject wrapobj;      public DataProvider Provider { get; set; }     public DataFileType FileType { get; private set; }     public DataEngine Engine { get; private set; }     public WrapColumn WrapCol { get => wrapcol; private set => wrapcol = value; }     public WrapObject WrapObj { get => wrapobj; private set => wrapobj = value; }      public Db()     {         // only used for public enum access     }      // For file databases without password set     public Db(string filepath)     {         FileType = GetDbFileType (filepath);         Engine = GetDbEngine (FileType);         Provider = GetDbProvider (FileType);         DataSource = filepath;         Database = Path.GetFileName (filepath);         Username = null;         Password = null;         ConnectionString = GetConnectionString (Provider);                   GetWrapCol (Engine);         GetWrapObj (Engine);     }      // For file databases with password set     public Db(string filepath, string password)     {         ... (same as first constructor)     }      // For server connections using windows auth     public Db(string path, string server , string database)     {         ... (same as first constructor)              }      // For all connection types     public Db(string path, string server, string database , string username , string password)     {         ... (same as first constructor)     }      public Db(int filetype_value, string server, string database)     {         ... (same as first constructor)     }      public Db(int filetype_value, string server, string database, string username , string password)     {         ... (same as first constructor)     }      /// <summary>     /// This changes the database connection string to use a different Provider.     /// </summary>     /// <param name="p"></param>     public void ReSetConnectionString(DataProvider p)     {         Provider = p;         ConnectionString = GetConnectionString ( Provider );     }      private DataFileType GetDbFileType(string path)     {         DataFileType ft;         string ext;         if (path.Contains ("."))         {             string fpath = path.Replace ("|DataDirectory|" , AppDomain.CurrentDomain.BaseDirectory);             ext = Path.GetExtension (fpath).Replace ("." , "").ToUpper ( );              if (Enum.TryParse<DataFileType> (ext , out ft) == true) return ft;         }         else         {             ft = (DataFileType) Enum.Parse (typeof (DataFileType) , path.ToUpper());            /// throw exception if extention is not in DataFileType enum or is null         }         return ft;     }      private string GetDataSource(DataEngine e, string path, string server)     {         if (DataSourceIsFile (e)) return path;         return server;     }      private DataFileType GetDbFileType(int enumvalue)     {         DataFileType ft = (DataFileType) Enum.Parse (typeof (DataFileType) , enumvalue.ToString ( ));        // throws and exception if int isn't in the DataFileType enum.         return ft;     }      public enum DataEngine     {         None,         ACCESS = 1,              // 0 = not applicable or not determined         MSSQL,         EXCEL,         ORACLE,         MYSQL,         TEXT     }      // <summary>     /// These are the int enum values that get stored in the database for each type of data file     /// </summary>     public enum DataFileType     {         None,         MDB = 1,       // 0 = not a configured data file         ACCDB,         MDF,           // Primary Data FIle         NDF,           // File Group (secondary data files)         XLS,           // Excel 97-2003 worksheet         XLSX,          // Excel 2007 workbook         XLSXM,         // Macro enabled workbook         XLTM,          // Binary worksheet (BIFF12)         XLW,           // Excel works space, previously known as workbook         CSV,           // Comma separated values         TAB,           // Tab separated values         TSV,           // Tab separated values         TXT            // Delimited Text file     }      /// <summary>     /// These are the int values that get stored in the database for each db connection     /// </summary>     public enum DataProvider     {         None,         Microsoft_ACE_OLEDB_12_0 = 1,          // Microsoft.ACE.OLEDB.12.0 - MS OLEDB DataProvider for MDB or ACCDB or EXCEL         Microsoft_ACE_OLEDB,               // Microsoft.ACE.OLEDB VersionIndependentProgID         Microsoft_Jet_OLEDB_4_0,           // MS Access - Does not work with ACCDB or any SQL Server version         Microsoft_Jet_OLEDB,               // Version Independent ProgID         SQLNCLI11,                         // SQL Server Native Client for OleDb         SQLNCLI,                           // Version Independent ProgID         SQLOLEDB_1,                        // SQL Server OleDb - Does not work with SQL Server Express         SQLOLEDB,                          // VersionIndependentProgID         SQL__Server__Native__Client__11_0, // SQL Server Native Client using ODbC         SQL__Server__Native__Client,       // Version Independent ProgID         MSDASQL_1,                         // Microsoft OleDb Data Access Components using ODbC         MSDASQL                            // Version Independent ProgID     }      private DataEngine GetDbEngine(int enumvalue)     {         DataEngine result = (DataEngine) Enum.Parse (typeof (DataEngine) , enumvalue.ToString ( ));        // throws and exception if int isn't in the DataEngine enum.         return result;     }      private DataEngine GetDbEngine(DataFileType ft)     {         switch (ft)         {             case DataFileType.MDB:                 return DataEngine.ACCESS;             case DataFileType.ACCDB:                 return DataEngine.ACCESS;             case DataFileType.MDF:                 return DataEngine.MSSQL;             case DataFileType.NDF:                 return DataEngine.MSSQL;             case DataFileType.XLS:                 return DataEngine.EXCEL;             case DataFileType.XLSX:                 return DataEngine.EXCEL;             case DataFileType.CSV:                 return DataEngine.TEXT;             case DataFileType.TAB:                 return DataEngine.TEXT;             case DataFileType.TSV:                 return DataEngine.TEXT;             case DataFileType.TXT:                 return DataEngine.TEXT;             default:                 throw new ArgumentException ($  "* * * DataFileType is not a supported data file format.  Database DataEngine could not be determined.");         }     }      private DataProvider GetDbProvider(DataFileType ft)     {         switch (ft)         {             case DataFileType.MDB:             case DataFileType.ACCDB:                 return DataProvider.Microsoft_ACE_OLEDB_12_0;             case DataFileType.MDF:                 return DataProvider.SQLNCLI11;                 // SQLOLEDB_1 and SQLOLEDB did not work with SQL Server Express             case DataFileType.NDF:                 return DataProvider.SQLNCLI11;             case DataFileType.XLS:             case DataFileType.XLSX:             case DataFileType.CSV:             case DataFileType.TAB:             case DataFileType.TSV:             case DataFileType.TXT:                 return DataProvider.Microsoft_ACE_OLEDB_12_0;             default:                 throw new ArgumentException ($  "* * * DataFileType is not a supported data file format.  Database DataProvider could not be determined.");         }     }      private void GetWrapCol(DataEngine e)     {         switch (e)         {             case DataEngine.ACCESS:                 WrapCol = new WrapColumn  { left = "`" , middle = "`,`" , right = "`" };                 break;             case DataEngine.MSSQL:                 WrapCol = new WrapColumn  { left = "[" , middle = "],[" , right = "]" };                 break;             case DataEngine.EXCEL:                 WrapCol = new WrapColumn  { left = "`" , middle = "`,`" , right = "`" };                 break;             case DataEngine.ORACLE:                 WrapCol = new WrapColumn  { left = @"""" , middle = @""",""" , right = @"""" };                 break;             case DataEngine.MYSQL:                 WrapCol = new WrapColumn  { left = "`" , middle = "`,`" , right = "`" };        // might be brackets for sysnames and ` for columns                 break;             case DataEngine.TEXT:                 WrapCol = new WrapColumn  { left = @"""" , middle = @""",""" , right = @"""" };        // not sure how to handle this yet                 break;             default:                 throw new ArgumentException ($  "* * * DataEngine was not valid. Could not determine a COLUMN escape character.");         }     }      private void GetWrapObj(DataEngine e)     {         switch (e)         {             case DataEngine.ACCESS:                 WrapObj = new WrapObject { left = "`" , middle = "`,`" , right = "`" };                 break;             case DataEngine.MSSQL:                 WrapObj = new WrapObject { left = "[" , middle = "],[" , right = "]" };                 break;             case DataEngine.EXCEL:                 WrapObj = new WrapObject { left = "`" , middle = "`,`" , right = "`" };                 break;             case DataEngine.ORACLE:                 WrapObj = new WrapObject { left = @"""" , middle = @""",""" , right = @"""" };                 break;             case DataEngine.MYSQL:                 WrapObj = new WrapObject { left = "[" , middle = "],[" , right = "]" };        // might be brackets for sysnames and ` for columns                 break;             case DataEngine.TEXT:                 WrapObj = new WrapObject { left = @"""" , middle = @""",""" , right = @"""" };        // not sure how to handle this yet                 break;             default:                 throw new ArgumentException ($  "* * * DataEngine was not valid. Could not determine a OBJECT escape character.");         }     }      private bool DataSourceIsFile(DataEngine e)     {         switch (e)         {             case DataEngine.ACCESS:                 return true;             case DataEngine.MSSQL:                 return false;             case DataEngine.EXCEL:                 return true;             case DataEngine.ORACLE:                 return false;             case DataEngine.MYSQL:                 return false;             case DataEngine.TEXT:                 return true;             default:                 throw new ArgumentException ($  "* * * DataEngine was not valid. Could not determine if this is a file or server DataSource.");         }     }        //https://docs.microsoft.com/en-us/dotnet/framework/data/adonet/connection-string-syntax?view=netframework-4.7.1     private string GetConnectionString(DataProvider Provider)     {         string ProgId = Provider.ToString ( ).Replace ("_" , ".");         string result = "";         switch (Provider)         {             case DataProvider.Microsoft_ACE_OLEDB_12_0:                                                           // Microsoft MS OLEDB for MDB or ACCDB or EXCEL             case DataProvider.Microsoft_ACE_OLEDB:                                                                // VersionIndependentProgID                 return $  @"Provider={ProgId};Data Source={DataSource};Persist Security Info=False;Jet OLEDB:Database Password={Password.EmptyIfNull ( )};";              case DataProvider.Microsoft_Jet_OLEDB_4_0:                                                            // MS Access Jet OLEDB - Does not work with ACCDB or any SQL Server version             case DataProvider.Microsoft_Jet_OLEDB:                                                             // VersionIndependentProgID                 // Jet db with user-lvel security requires a Workgroup information file designation:                 // Jet OLEDB:System Database=|DataDirectory|\System.mdw;"   <--- that could be stored in the Server field                 // Jet user-level security uses the User ID and Password setting.  A new constructer that includes the Username field will need to be added to support this                  if (Engine == DataEngine.ACCESS && Password.NullIfEmpty() == null)                     return $  @"Provider={ProgId};Data Source={DataSource};User ID=Admin;Password=;";                 else                     return $  @"Provider={ProgId};Data Source={DataSource};Persist Security Info=False;Jet OLEDB:Database Password={Password.EmptyIfNull ( )};";               case DataProvider.SQLNCLI11:                                                                          // SQL Server OleDb Native Client             case DataProvider.SQLNCLI:                                                                            // VersionIndependentProgID                 result = $  @"Provider={ProgId};Server={DataSource};Database={Database};";                 if (Password != null) result += $  "Uid={Username.EmptyIfNull ( )};Pwd={Password.EmptyIfNull ( )};";                 if (Password == null) result += "Integrated Security=SSPI;";                         return result;              case DataProvider.SQLOLEDB_1:                                                                         // Microsoft OLE DB DataProvider for SQL Server (I've seen this work for ACCESS also) - DID NOT work for SQL Server 2016 Express, but DID work for SQL Server 2016 Developer Edition             case DataProvider.SQLOLEDB:                                                                           // VersionIndependentProgID                 result = $  @"Provider={ProgId};Data Source={DataSource};Initial Catalog={Database};";                 if (Password != null) result += $  "User Id={Username.EmptyIfNull()};Password={Password.EmptyIfNull ( )};";                 if (Password == null) result += "Integrated Security=SSPI;";                                                                                                             return result;              case DataProvider.MSDASQL_1:                                                                          // Microsoft Data Access OleDb using ODbC             case DataProvider.MSDASQL:                                                                            // VersionIndependentProgID                 if (Engine == DataEngine.ACCESS)                     return $  @"Driver={{Microsoft Access Driver (*.mdb, *.accdb)}};DbQ={DataSource}";                 if (Engine == DataEngine.EXCEL)                     return $  @"Driver={{Microsoft Excel Driver (*.xls, *.xlsx, *.xlsm, *.xlsb)}};DbQ={DataSource}";                 if (Engine == DataEngine.MSSQL)                     if (string.IsNullOrEmpty (Username))                         return $  @"[DataProvider = MSDASQL;] DRIVER={{SQL Server}}; SERVER={DataSource}; DATABASE={Database};UID=;Integrated Security=SSPI";                     else                         return $  @"[DataProvider = MSDASQL;] DRIVER={{SQL Server}}; SERVER={DataSource}; DATABASE={Database};UID={Username};PWD={Password}";                 else                     throw new ArgumentException ($  " * * * The MSDASQL Provider has only been set up for MS Access or Excel or MSSQL connections.  Could not create Connection String");               case DataProvider.SQL__Server__Native__Client__11_0:                                        // SQl Server OleDb using ODbC                 if (Engine == DataEngine.MSSQL && (Username.NullIfEmpty ( ) != null))                     return $  @"Driver={{{ProgId}}};Server={DataSource};Database={Database};Uid={Username};Pwd={Password};";                 else                     return $  @"Driver={{{ProgId}}};Server={DataSource};Database={Database};Trusted_Connection=yes;";              default:                 throw new ArgumentException ($  " * * * DataProvider is not valid.  Could not create Connection String");         }     }      public string Columns(string value)     {         string[ ] c = value.Split (',');                                                        // if col names have "," in them, maybe replace it with another char and modify this method to replace it back.         return $  "{WrapCol.left}{string.Join(WrapCol.middle , c)}{WrapCol.right}";     }    }   public static class StringExt {     public static string NullIfEmpty(this string value)     {         return string.IsNullOrEmpty (value) ? null : value;     }      public static string EmptyIfNull(this string value)     {         if (string.IsNullOrEmpty (value))             return string.Empty;         else             return value;     }  } }