Reasons for Redundant AsQueryable() Calls When Upgrading to .NET 6

As someone who writes .NET 6 code directly, you might encounter code like DbContext.Table.AsQueryable() when looking at projects upgraded from .NET Core 3.1. You might wonder why AsQueryable() is needed when DbSet<TEntity> already implements IQueryable<TEntity>, especially since removing it often seems to work fine. If you encounter this, check if the project has the System.Linq.Async package installed.

In versions prior to Microsoft.EntityFrameworkCore 5, the interfaces implemented by DbSet<TEntity> were as follows:

public abstract class DbSet<TEntity> : Microsoft.EntityFrameworkCore.Infrastructure.IInfrastructure<IServiceProvider>, System.Collections.Generic.IAsyncEnumerable<TEntity>, System.Collections.Generic.IEnumerable<TEntity>, System.ComponentModel.IListSource, System.Linq.IQueryable<TEntity> where TEntity : class

The Queryable class defines extension methods Where() and Select() for IQueryable<TEntity>.

Meanwhile, the AsyncEnumerable class in System.Linq.Async defines extension methods Where() and Select() for IAsyncEnumerable<TSource>. This caused ambiguity, as DbSet<TEntity> could not determine which extension method to call. Developers had to use AsQueryable() to explicitly cast the type to IQueryable<TEntity>. Consequently, projects upgraded from older versions often contain many redundant AsQueryable() calls.

In Microsoft.EntityFrameworkCore 6 and later versions, the interfaces implemented by DbSet<TEntity> are as follows:

public abstract class DbSet<TEntity> : Microsoft.EntityFrameworkCore.Infrastructure.IInfrastructure<IServiceProvider>, System.Collections.Generic.IEnumerable<TEntity>, System.ComponentModel.IListSource, System.Linq.IQueryable<TEntity> where TEntity : class

Therefore, even with System.Linq.Async installed, there will be no ambiguity issues regarding method calls.

Revision History

• 2024-07-16 Initial version created.