Light ORM

DbApi applies to relational DBMS respecting some interfaces from System.Data assembly of .Net. It's a tiny set of classes helping object instanciation from a query result. Object instanciation is done by reflection. DbApi projects depends on Oracle.DataAccess.Client only for the OracleWrapper and OraCommandDescriptorwhich define shortcuts to use with an Oracle Database. Others wrappers could be defined to extends DbApi to other DBMS.

Example

Giving a query returning a cursor as follow :

ID    Number
NAME  Varchar2
AGE   Number

Giving a class like (it just needs to have a no parameter constructor and tagged properties to match query result fields) :

[DbObject("Person")]
public class Person
{
    [DbAttribute("ID")]
    public int Id { get; set; }
    [DbAttribute("NAME")]
    public string Name { get; set; }
    [DbAttribute("AGE")]
    public int Age { get; set; }
    public string DummyProp;
}

Instanciating a Person collection will simply be (for a simple select query from PERSONS table) :

public Person[] ReadAllPersons()
{
    const string connectionString = "Data Source=service;User Id=user;Password=pwd;";

    OracleWrapper oracleWrapper = new OracleWrapper(connectionString);
    Person[] ret = oracleWrapper.GetData<Person>("SELECT * FROM PERSONS").ToArray();

    return ret;
}

Or for a stored procedure PKG_READ.GET_PERSONS which returns described result above (can also be done with an OraCommandDescriptor) :

public Person[] ReadAllPersonsFromProc()
{
    const string connectionString = "Data Source=service;User Id=user;Password=pwd;";
    
    List<OracleParameter> oraParameters = new List<OracleParameter>();
    oraParameters.Add(new OracleParameter("p_return_code", OracleDbType.Int32, ParameterDirection.Output));
    oraParameters.Add(new OracleParameter("p_sql_code", OracleDbType.Int32, ParameterDirection.Output));
    oraParameters.Add(new OracleParameter("p_error_text", OracleDbType.Varchar2, ParameterDirection.Output));
    oraParameters.Add(new OracleParameter("cur_out", OracleDbType.RefCursor, ParameterDirection.Output));
    
    OracleWrapper oracleWrapper = new OracleWrapper(connectionString);
    Person[] ret = oracleWrapper.GetData<Person>("PKG_READ.GET_PERSONS", oraParameters).ToArray();

    return ret;
}

Details

Two classes are define for properties tagging.

Mapper

It wraps DBMS commands.

ICommandDescriptor

It is an interface packing command parameters.

OraCommandDescriptor

An implementation of ICommandDescriptor for Oracle.

Readers

Provides main classes.

LambdaDataReader

Allows retrieving generic collection from a query using IDataReader and DataReflectionReader. Is IDisposable, manages DBMS connection and resources disposing.

DataReflectionReader

Instanciate object mapping public properties witch DbAttribute value equals query field name. Uses a Dictionary<string, PropertyInfo> as a cache for performance reasons (reflection may be dramatically slow).

OracleWrapper

Is an implementation of a LambdaDataReader specifying connection and command for Oracle®. Provides an easy way to get data from an oracle database.

Note

Compatibility

Given csproj has been generated with Visual Studio 2013®.

About perfs

More tests have to be done. Treatments seem to be about as fast as explicit instanciation on a 1200 rows and 20 columns table.

gliluaume/DbApi