SequelNet

SQL abstraction/generalization/protection layer.

Current connectors available:

• MySql
• MySql2
• MsSql
• Postgre (not tested too much)
• OleDb (requires .NET Framework).

This library allows you fluent SQL building, even for very complex queries.
It has a built-in capability of reading/writing records from classes - in a very different way than in Entity Framework.
It it less automated, which means you have to have your record class inherit from AbstractRecord and supply the definition of the schema.
But - that very definition of the schema allows to manage the whole database lifecycle from the code, including creating from scratch, migrations etc.
It also allows matching value types according to the schema when applicable.

The magic happens in the little SchemaGenerator addon for Visual Studio.
This little guys takes a "pseudo-script" and converts it to a full code of an AbstractRecord record.
You can override/extend almost anything in there, either in the script itself, or by defining a partial class and adding stuff.

A little bit of history

This used to be dg.Sql library, renamed to SequelNet.
Migration notes - in the Releases section, for 2.0.0.

Usage

The use is pretty straight-forward. To supply a default connector, add a SequelNet.Connector key in the appSettings of web.config. Like this:

    <add key="SequelNet.Connector" value="MySql2" />

To supply a default connection string, add a SequelNet connection string in web.config, or SequelNet::ConnectionString key in app config.
Another option is to add a SequelNet::ConnectionStringKey key in the app config, which specifies the connectionString's name to be used.

Structure of this library

• Query: Build the query, and executes in a number of different ways, and different way to retrieve the results
• ConnectorBase is the base class for the connector layer. Each connector has a subclass of this class, which supplies the basic functionalities, similar to the SqlConnection class. (I am considering a change this class's name in the future...)
• DataReaderBase is the same story as with ConnectorBase, providing the same functionality as SqlDataReader
• AbstractRecord is a DAL class that represents your data, and contains a TableSchema, data accessors, and helper functions. Using AbstractRecord is completely optional!
• TableSchema is a class representing the an actual db schema. This assists the Query in converting values where necessary, bulding queries or even building CREATE TABLE, ALTER TABLE and CREATE INDEX queries...
• There's a namespace Phrases which includes many objects that wrap native sql functions. You can add your own, based on the IPhrase class.

Detecting database errors

Use ConnectorBase.GetDatabaseError(exception) to detect database errors without referencing a driver exception type or checking numeric error codes:

using SequelNet.Connector;

try
{
    query.Execute(connector);
}
catch (Exception ex) when (connector.GetDatabaseError(ex) == DatabaseError.UniqueViolation)
{
    // Handle a primary-key or unique-key collision.
}

UniqueViolation means duplicate values in a primary key or unique key. The Duplicate* categories mean duplicate names or definitions; Undefined* categories mean missing objects, including missing drop targets.

Category	MySQL (both drivers)	SQL Server	PostgreSQL SQLSTATE	Jet/ACE SQLState
UniqueViolation	1062	2601, 2627	23505	3022
ForeignKeyViolation	1452	See ConstraintViolation	23503	3200, 3201
ConstraintViolation	—	547	—	—
DuplicateColumn	1060	2705	42701	3191, 3380
DuplicateTable	1050	—	42P07	3010
DuplicateIndex	1061	—	—	3284, 3375
DuplicateObject	—	1913, 2714	42710	3012, 3283
UndefinedColumn	1054	207, 4924	42703	3381
UndefinedTable	—	—	42P01	3376
UndefinedObject	1091	3728	42704	3372

Some provider conditions have broader meanings:

• PostgreSQL 42P07 maps to DuplicateTable, matching its native condition name, but also covers duplicate indexes and other relations. 42710 maps separately to DuplicateObject. See PostgreSQL's error codes and index creation source.
• SQL Server 547 covers foreign-key and check constraints, so it returns ConstraintViolation. 1913 covers both indexes and statistics, and 2714 covers multiple object kinds, so both return DuplicateObject. See Microsoft's error reference.
• OleDb examines Jet/ACE engine error records and reads Access error numbers from OleDbError.SQLState. NativeError may contain a different internal number. Error records from other OLE DB providers remain Unknown. Jet's generic missing-parameter errors also remain Unknown, since they do not uniquely identify a missing column. See the Access error catalogue.

SQL Server and OleDb return the first recognized category from their error collection. The Jet 4.0 mappings were exercised against a real temporary database; ACE was not installed on the validation machine.

Classification does not open a connection or change the exception. Null, unrecognized errors, exceptions from other drivers, and connectors without a classification implementation return DatabaseError.Unknown. Wrapped exceptions are not unwrapped; pass the underlying provider exception explicitly if needed.

Bonus

If you're using MySql, then there's a MySqlBackup class, which can create a full backup of a Database, including shcema and data. Yes, I know, it's cool.

SchemaGenerator

There's a Visual Studio AddIn, called the "SchemaGenerator", which assists in creating the TableSchema and a matching AbstractRecord based on a simple language which resides in a comment.

This little tool makes rapid db prototyping easy, and gets you much further in development in significantly less time than when using any other tool I've used.

Full documentation of the syntax in Macro Structure.MD.

License

All the code here is under MIT license. Which means you could do virtually anything with the code. I will appreciate it very much if you keep an attribution where appropriate.

The MIT License (MIT)

Copyright (c) 2013 Daniel Cohen Gindi (danielgindi@gmail.com)

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The above copyright notice and this permission notice shall be included in all
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