Question 1

How to set up CommandQuery in an ASP.NET Core API?

Accepted Answer

Use the CommandQuery.AspNetCore package and follow the sample in CommandQuery.Sample.AspNetCore, which demonstrates configuring handlers and endpoints with minimal boilerplate. The README for that package provides specific setup instructions.

Question 2

CommandQuery vs MediatR: which is better for CQS in .NET?

Accepted Answer

CommandQuery is more focused on pragmatic CQS with multi-platform support out-of-the-box, while MediatR has a larger ecosystem and more middleware options. Choose CommandQuery for serverless or multi-cloud scenarios; MediatR for richer pipeline features in traditional apps.

Question 3

Can commands return values in CommandQuery?

Accepted Answer

Yes, CommandQuery pragmatically allows commands to return results, unlike strict CQS, as mentioned in the philosophy. This provides flexibility for cases like returning IDs or status after mutations.

Question 4

What's the difference between the AWS Lambda and Azure Functions packages?

Accepted Answer

Both packages adapt CommandQuery for serverless environments, but they integrate with platform-specific triggers and contexts. The AWS Lambda package uses Amazon.Lambda.APIGatewayEvents, while Azure Functions uses HttpRequest, as indicated in the sample code and upgrading notes.

Question 5

How to handle validation in CommandQuery handlers?

Accepted Answer

Validation is not built-in; developers must implement it manually in handlers or use custom middleware. The library focuses on separation of concerns, so you'll need to add validation logic using .NET attributes or third-party libraries.

Question 6

Is there a way to test CommandQuery handlers easily?

Accepted Answer

Yes, the project includes test samples like CommandQuery.Sample.AspNetCore.Tests that show how to unit test handlers by mocking dependencies. The abstraction layers make handlers straightforward to test in isolation.

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