linq2db 6.5.0

LINQ to DB

• Standout Features
  • Related Linq To DB and 3rd-party projects
• Configuring connection strings
  • Passing Into Constructor
  • Using Config File (.NET Framework)
  • Using Connection String Settings Provider
  • Use with ASP.NET Core and Dependency Injection
• Define POCO class
  • Configuration using mapping attributes
  • Fluent Configuration
  • Inferred Configuration
  • DataConnection class
• Queries
  • Selecting Columns
  • Composing queries
  • Paging
  • Joins
  • Creating your POCOs
  • Insert
  • Update
  • Delete
  • Bulk Copy
  • Transactions
  • Merge
  • Window (Analytic) Functions
• Analyzers
• MiniProfiler
• More

LINQ to DB is the fastest LINQ database access library offering a simple, light, fast, and type-safe layer between your POCO objects and your database.

Architecturally it is one step above micro-ORMs like Dapper, Massive, or PetaPoco, in that you work with LINQ expressions, not with magic strings, while maintaining a thin abstraction layer between your code and the database. Your queries are checked by the C# compiler and allow for easy refactoring.

However, it's not as heavy as LINQ to SQL or Entity Framework. There is no change-tracking, so you have to manage that yourself, but on the positive side you get more control and faster access to your data.

In other words LINQ to DB is type-safe SQL.

Standout Features

• Rich Querying API:
  • Explicit Join Syntax (In addition to standard LINQ join syntax)
  • CTE Support
  • Bulk Copy/Insert
  • Window/Analytic Functions
  • Merge API
• Extensibility:
  • Ability to Map Custom SQL to Static Functions

See Github.io documentation for more details.

Code examples and demos can be found here or in tests.

Related Linq To DB and 3rd-party projects

• linq2db.EntityFrameworkCore (adds support for linq2db functionality in EF.Core projects)
• LinqToDB.Identity - ASP.NET Core Identity provider using Linq To DB
• LINQPad Driver
• DB2 iSeries Provider
• ASP.NET Core Template
• PostGIS extensions for linq2db

Notable open-source users:

• nopCommerce - popular open-source e-commerce solution
• OdataToEntity - library to create OData service from database context
• SunEngine - site, blog and forum engine

Configuring connection strings

Passing Into Constructor

You can simply pass connection string into DataConnection or DataContext constructor using DataOptions class.

Minimal configuration example:

var db = new DataConnection(
  new DataOptions()
    .UseSqlServer(@"Server=.\;Database=Northwind;Trusted_Connection=True;"));

Use connection configuration action to setup SqlClient-specific authentication token:

var options = new DataOptions()
  .UseSqlServer(connectionString, SqlServerVersion.v2017, SqlServerProvider.MicrosoftDataSqlClient)
  .UseBeforeConnectionOpened(cn =>
    {
        ((SqlConnection)cn).AccessToken = accessToken;
    });

// pass configured options to data context constructor
var dc = new DataContext(options);

Using Config File (.NET Framework)

In your web.config or app.config make sure you have a connection string (check this file for supported providers):

<connectionStrings>
  <add name="Northwind" 
    connectionString = "Server=.\;Database=Northwind;Trusted_Connection=True;" 
    providerName     = "SqlServer" />
</connectionStrings>

Using Connection String Settings Provider

Alternatively, you can implement custom settings provider with ILinqToDBSettings interface, for example:

public class ConnectionStringSettings : IConnectionStringSettings
{
    public string ConnectionString { get; set; }
    public string Name             { get; set; }
    public string ProviderName     { get; set; }
    public bool   IsGlobal         => false;
}

public class MySettings : ILinqToDBSettings
{
    public IEnumerable<IDataProviderSettings> DataProviders
        => Enumerable.Empty<IDataProviderSettings>();

    public string DefaultConfiguration => "SqlServer";
    public string DefaultDataProvider  => "SqlServer";

    public IEnumerable<IConnectionStringSettings> ConnectionStrings
    {
        get
        {
            // note that you can return multiple ConnectionStringSettings instances here
            yield return
                new ConnectionStringSettings
                {
                    Name             = "Northwind",
                    ProviderName     = ProviderName.SqlServer,
                    ConnectionString =
                        @"Server=.\;Database=Northwind;Trusted_Connection=True;"
                };
        }
    }
}

And later just set on program startup before the first query is done (Startup.cs for example):

DataConnection.DefaultSettings = new MySettings();

Use with ASP.NET Core and Dependency Injection

See article.

Define POCO class

You can generate POCO classes from your database using linq2db.cli