Ways to instantiate PetaPoco

There are various way to construct a new instance PetaPoco, each solving a particular use case.

The API, as it stands, comprises:

public Database()
public Database(IDbConnection connection)
public Database(string connectionString, string providerName = null)
public Database(string connectionString, DbProviderFactory factory)
public Database(string connectionStringName)
public Database(string connectionString, IProvider provider)

General information

Version 5.1.84 or greater does not require a DbProviderFactory registration for any particular SQL client. However, there is potential for a minor got-cha here, as the provider name still needs to be set as PetaPoco uses this to choose correct DB provider. A list of valid provider names is given below.

Note: Users of the T4 templates will still require a DbProviderFactory registration, a valid .net provider name, and the additional GAC registration of their selected SQL client. For more detailed instructions for the T4 template usage, please read the top of the T4 include file.

Provider names

Valid provider names are:

Provider	Accepted provider names
MySqlDatabaseProvider	MySql,MySql.Data.MySqlClient
PostgreSQLDatabaseProvider	Npgsql, pgsql
SQLiteDatabaseProvider	SQLite,System.Data.SQLite
SqlServerCEDatabaseProviders	SqlServerCe, SqlCeConnection, System.Data.SqlServerCe.4.0
OracleDatabaseProvider	Oracle, Oracle.ManagedDataAccess.Client
SqlServerDatabaseProvider (Default)	SqlServer, System.Data.SqlClient

Sample provider name in use.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <connectionStrings>
    <add name="SomeName" connectionString="SomeConnectionString" providerName="Npgsql"/>
  </connectionStrings>
</configuration>

Note: the casing of the provider name does not matter.

Each constructor option explained

`public Database()`

The parameterless constructor is a quick and easy way to create a new instance of PetaPoco. This constructor will use the first connection string it finds in the app/web configuration.

Sample postgre app/web configuration file.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <connectionStrings>
    <add name="postgres" connectionString="Host=127.0.0.1;Username=petapoco;Password=petapoco;Database=petapoco;Port=5001;" providerName="Npgsql"/>
  </connectionStrings>
</configuration>

`public Database(IDbConnection connection)`

The constructor which takes an instance of an existing connection is one of PetaPoco's more interesting and less known features. The why lies with the use case. It's not hard to imagine a situation where a project uses its own implementation of a DAL or a product like EF and has a need to easily access/manipulate data. In such a case, one can simply acquire a IDbConnection and construct an instance of PetaPoco for easy data access and manipulation.

Note: Please be aware that PetaPoco does not take ownership of the connection management when using this constructor, that responsibility to left to the caller.

`public Database(string connectionString, string providerName = null)`

With this constructor one simply provides a connection string and optional provider name. If no provider name is given, the default SQL Server provider is used. A table of valid provider names can be found here.

`public Database(string connectionStringName)`

Hopefully this one is fairly obvious. If you guessed it maps the given connection string name to a connection string in the app/web config with the same name, then congrats for you.

Note: Ensure you give the connection string entry a valid provider name. A table of valid provider names can be found here. If no provider name is set, the default SQL Server provider is used.

Sample MySQL app/web configuration file.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <connectionStrings>
        <add name="mysql" connectionString="Server=127.0.0.1;Uid=petapoco;Pwd=petapoco;Database=petapoco;Port=5002" providerName="MySql" />        
    </connectionStrings>
</configuration>