ABP version 4.2 Migration Guide

This version has no breaking changes but there is an important change on the repositories that should be applied for your application for an important performance and scalability gain.

IRepository.GetQueryableAsync

IRepository interface inherits IQueryable, so you can directly use the standard LINQ extension methods, like Where, OrderBy, First, Sum... etc.

Example: Using LINQ directly over the repository object

public class BookAppService : ApplicationService, IBookAppService
{
    private readonly IRepository<Book, Guid> _bookRepository;

    public BookAppService(IRepository<Book, Guid> bookRepository)
    {
        _bookRepository = bookRepository;
    }

    public async Task DoItInOldWayAsync()
    {
        //Apply any standard LINQ extension method
        var query = _bookRepository
            .Where(x => x.Price > 10)
            .OrderBy(x => x.Name);

        //Execute the query asynchronously
        var books = await AsyncExecuter.ToListAsync(query);
    }
}

See the documentation if you wonder what is the AsyncExecuter.

Beginning from the version 4.2, the recommended way is using IRepository.GetQueryableAsync() to obtain an IQueryable, then use the LINQ extension methods over it.

Example: Using the new GetQueryableAsync method

public async Task DoItInNewWayAsync()
{
    //Use GetQueryableAsync to obtain the IQueryable<Book> first
    var queryable = await _bookRepository.GetQueryableAsync();

    //Then apply any standard LINQ extension method
    var query = queryable
        .Where(x => x.Price > 10)
        .OrderBy(x => x.Name);

    //Finally, execute the query asynchronously
    var books = await AsyncExecuter.ToListAsync(query);
}

ABP may start a database transaction when you get an IQueryable (If current Unit Of Work is transactional). In this new way, it is possible to start the database transaction in an asynchronous way. Previously, we could not get the advantage of asynchronous while starting the transactions.

The new way has a significant performance and scalability gain. The old usage (directly using LINQ over the repositories) will be removed in the next major version (5.0). You have a lot of time for the change, but we recommend to immediately take the action since the old usage has a big scalability problem.

Actions to Take

• Use the repository's queryable feature as explained before.
• If you've overridden CreateFilteredQuery in a class derived from CrudAppService, you should override the CreateFilteredQueryAsync instead and remove the CreateFilteredQuery in your class.
• If you've overridden WithDetails in your custom repositories, remove it and override WithDetailsAsync instead.
• If you've used DbContext or DbSet properties in your custom repositories, use GetDbContextAsync() and GetDbSetAsync() methods instead of them.

You can re-build your solution and check the Obsolete warnings to find some of the usages need to change.

About IRepository Async Extension Methods

Using IRepository Async Extension Methods has no such a problem. The examples below are pretty fine:

var countAll = await _personRepository
    .CountAsync();

var count = await _personRepository
    .CountAsync(x => x.Name.StartsWith("A"));

var book1984 = await _bookRepository
    .FirstOrDefaultAsync(x => x.Name == "John");   

See the repository documentation to understand the relation between IQueryable and asynchronous operations.

.NET Package Upgrades

ABP uses the latest 5.0.* .NET packages. If your application is using 5.0.0 packages, you may get an error on build. We recommend to depend on the .NET packages like 5.0.* in the .csproj files to use the latest patch versions.

Example:

<PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="5.0.*" />

Blazorise Library Upgrade

If you are upgrading to 4.2, you also need also upgrade the following packages in your Blazor application;

• Blazorise.Bootstrap to 0.9.3-preview6
• Blazorise.Icons.FontAwesome to 0.9.3-preview6