Raiqub.Expressions.Marten 1.0.34

Expressions

Raiqub.Expressions is a library that provides abstractions for creating specifications and query models using LINQ expressions. It also supports querying and writing to databases using various providers.

🏃 Quickstart   |   📗 Guide   |   📦 NuGet

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Features

• Abstractions for creating specifications and query models
• Abstractions for querying and writing to databases
• Supports Entity Framework Core and Marten providers
• Built with .NET Standard 2.0, 2.1, and .NET Core 6.0

NuGet Packages

• Raiqub.Expressions: abstractions for creating specifications
• Raiqub.Expressions.Reading: abstractions for creating query models and query sessions and querying from database (defines IDbQuerySessionFactory and IDbQuerySession interfaces)
• Raiqub.Expressions.Writing: abstractions for creating write sessions and writing to database (defines IDbSessionFactory and IDbSession interfaces)
• Raiqub.Expressions.EntityFrameworkCore: implementation of sessions and factories using Entity Framework Core
• Raiqub.Expressions.Marten: implementation of sessions and factories using Marten library

Prerequisites

Before you begin, you'll need the following:

• .NET Standard 2.0 or 2.1, or .NET Core 6.0 installed on your machine
• An IDE such as Visual Studio, Visual Studio Code, or JetBrains Rider
• A database to query against (if using the reading package) or write to (if using the writing package)

Quickstart

To use the library, you can install the desired NuGet package(s) in your project and start creating your specifications and query models. Here's an example of how to create a simple specification:

public class CustomerIsActive : Specification<Customer>
{
    public override Expression<Func<Customer, bool>> ToExpression()
    {
        return customer => customer.IsActive;
    }
}

And here's an example of how to use the specification:

// session is of type IDbSession or IDbQuerySession and can be injected
var query = session.Query(new CustomerIsActive());
var customers = await query.ToListAsync();

Guide

To use Raiqub.Expressions in your project, follow these steps:

1. Install the required NuGet package(s) for the database provider you'll be using, such as `Microsoft.EntityFrameworkCore.SqlServer` for Entity Framework Core or `Marten` for Marten.

2. Install the `Raiqub.Expressions.EntityFrameworkCore` package if using Entity Framework or the `Raiqub.Expressions.Marten` package if using Marten.

3. Register the session and session factories using the appropriate extension method(s) for your database provider:

   For Entity Framework Core:

   // The DbContext must be registered calling AddDbContextFactory<YourDbContext>()
   services.AddEntityFrameworkExpressions()
       .AddSingleContext<YourDbContext>();
   

   For Marten:

   services.AddMartenExpressions()
       .AddSingleContext();
   

4. Inject the appropriate session interface (IDbQuerySession for read sessions, IDbSession for write sessions) into your services, and use it read and write from/to database.

Creating Query Models and Specifications

The `Raiqub.Expressions` package provides abstractions for creating specifications and query models. You can create a new query model by creating a new class that derives from `QueryModel<TSource, TResult>`. Similarly, you can create a new specification by creating a new class that derives from `Specification<T>`.

Here's an example of a query model that filters a list of entities based on a set of conditions:

public class MyQueryModel : QueryModel<MyEntity, MyResult>
{
    protected override IEnumerable<Specification<MyEntity>> GetPreconditions()
    {
        yield return new MyEntityIsEnabledSpecification();
    }

    protected override IQueryable<MyResult> ExecuteCore(IQueryable<MyEntity> source)
    {
        return source.OrderBy(e => e.Name).Select(e => new MyResult { Id = e.Id, Name = e.Name });
    }
}

And here's an example of a specification that checks if an entity is enabled:

public class MyEntityIsEnabled : Specification<MyEntity>
{
    public override Expression<Func<MyEntity, bool>> ToExpression()
    {
        return entity => entity.IsEnabled;
    }
}

Creating Query Sessions and Querying Data

To create a query session and query data using a query model, follow these steps:

1. Inject an instance of `IDbQuerySessionFactory` into your service or controller.
2. Use the `Create()` method of the `IDbQuerySessionFactory` interface to create a new query session.
3. Call the `Query()` method on the query session, passing in your query model or specification instance.
4. Call one of the methods on the resulting `IDbQuery<T>` interface to execute the query and retrieve the results.

await using (var session = querySessionFactory.Create())
{
    IDbQuery<Customer> query = session.Query(new CustomerIsActive());
    IReadOnlyList<Customer> customers = await query.ToListAsync();
}

Creating Write Sessions and Writing Data

To create a write session and write data to the database, follow these steps:

1. Inject an instance of `IDbSessionFactory` into your service or controller.
2. Use the `Create()` method of the `IDbSessionFactory` interface to create a new write session.
3. Call the appropriate methods on the write session to perform insert, update, or delete operations on your entities.
4. Call the `SaveChangesAsync()` method on the write session to persist your changes to the database.

await using (var session = sessionFactory.Create())
{
    var blog = new Blog { Url = "https://example.com" };
    session.Add(blog);
    await session.SaveChangesAsync();
}

Defining custom SQL query for entity (Entity Framework)

To define a custom SQL query for retrieving a entity from database, follow these steps:

1. Create a new class implementing the `ISqlProvider<TEntity>` interface;
2. Implement the `GetQuerySql()` method returning a raw or an interpolated SQL string;
3. Register the created class as a implementation of ISqlProvider interface for dependency injection using the singleton lifetime.

Example implementing a custom SQL query for Blog entity:

private class BlogSqlProvider : ISqlProvider<Blog>
{
    public SqlString GetQuerySql() => SqlString.FromSqlInterpolated($"SELECT \"Id\", \"Name\" FROM \"Blog\"");
}

And then, registering it:

services.AddSingleton<ISqlProvider, BlogSqlProvider>();

Supported Databases

Currently, Raiqub.Expressions supports the following database libraries:

• Entity Framework Core
• Marten

If you need to use another database, you will need to implement your own database session factory and database session implementing `IDbSessionFactory` and `IDbSession` interfaces.

Contributing

If something is not working for you or if you think that the source file should change, feel free to create an issue or Pull Request. I will be happy to discuss and potentially integrate your ideas!

License

This library is licensed under the MIT License.