Introduction

When developing an ASP.NET Core application and using Entity Framework (especially when using HotChocolate GraphQL library) to manage your database, you may encounter the following error:

Cannot access a disposed context instance. A common cause of this error is disposing a context instance that was resolved from dependency injection and then later trying to use the same context instance elsewhere in your application.

Cause

This error typically occurs when a database context (DbContext) is attempted to be used after it has been disposed. This often happens in scenarios where the DbContext instance is not properly managed within your Dependency Injection (DI) system.

Solution

Use the Factory Pattern

The solution to this error is to use factory pattern to create a new instance of the DbContext each time it is needed. This way, you can avoid issues with managing the lifecycle of instances.

1. Register the Factory in the DI Container:

   In your Program.cs:

   var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");
   builder.Services..AddDbContextFactory<LibreBorrDbContext>(options => {
           options.UseSqlServer(connectionString); // or whatever DB server you are using
   });
   

2. Use the Factory in Your Service:

   In your service (BookService):

   public class BookService : IBookService
   {
       private readonly IDbContextFactory _dbContextFactory;
   
       public BookService(IDbContextFactory dbContextFactory)
       {
           _dbContextFactory = dbContextFactory;
       }
   
       public async Task<List<Book>> GetBooks()
       {
           await using var context = _dbContextFactory.CreateDbContext();
           return await context.Books.ToListAsync();
       }
   }
   

Conclusion

Using the factory pattern for managing DbContext instances allows you to avoid issues with disposal and lifecycle management of the context. This method provides greater control over the context and helps you eliminate errors like Cannot access a disposed context instance.

If you have any further questions or need assistance, feel free to reach out! 😊