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Published 20 hours ago • verified publisher icon hlaueriksson
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Command Query Separation for 🌐ASP.NET Core ⚡AWS Lambda ⚡Azure Functions ⚡Google Cloud Functions

CommandQuery

build CodeFactor

CommandQuery CommandQuery.Abstractions CommandQuery.Client

CommandQuery.AspNetCore CommandQuery.AWSLambda CommandQuery.AzureFunctions CommandQuery.GoogleCloudFunctions CommandQuery.AspNet.WebApi

Content

  • Introduction
  • Packages
    • CommandQuery ⚙️
    • CommandQuery.AspNetCore 🌐
    • CommandQuery.AWSLambda ⚡
    • CommandQuery.AzureFunctions ⚡
    • CommandQuery.GoogleCloudFunctions ⚡
    • CommandQuery.Client 🧰
    • CommandQuery.AspNet.WebApi 🌐
  • Upgrading
  • Acknowledgements

Introduction

Command Query Separation (CQS) for .NET and C#

  • Build services that separate the responsibility of commands and queries
  • Focus on implementing the handlers for commands and queries
  • Create APIs with less boilerplate code

Available for:

🌐 ASP.NET Core
⚡ AWS Lambda
⚡ Azure Functions
⚡ Google Cloud Functions
🌐 ASP.NET Web API 2

Command Query Separation?

Queries: Return a result and do not change the observable state of the system (are free of side effects).

Commands: Change the state of a system but do not return a value.

— Martin Fowler

In other words:

  • Commands
    • Writes (create, update, delete) data
  • Queries
    • Reads and returns data

The traditional approach that commands do not return a value is a bit inconvenient.

CommandQuery has a pragmatic take and supports both commands with and without result 👍

Packages

CommandQuery ⚙️

NuGet NuGet

Command Query Separation for .NET

  • 📃 README: CommandQuery.md
  • 💁 Samples:
    • CommandQuery.Sample.Contracts
    • CommandQuery.Sample.Handlers

CommandQuery.AspNetCore 🌐

NuGet NuGet

Command Query Separation for ASP.NET Core

  • 📃 README: CommandQuery.AspNetCore.md
  • 💁 Samples:
    • CommandQuery.Sample.AspNetCore.V3
    • CommandQuery.Sample.AspNetCore.V3.Tests
    • CommandQuery.Sample.AspNetCore.V5
    • CommandQuery.Sample.AspNetCore.V5.Tests

CommandQuery.AWSLambda ⚡

NuGet NuGet

Command Query Separation for AWS Lambda

  • 📃 README: CommandQuery.AWSLambda.md
  • 💁 Samples:
    • CommandQuery.Sample.AWSLambda
    • CommandQuery.Sample.AWSLambda.Tests

CommandQuery.AzureFunctions ⚡

NuGet NuGet

Command Query Separation for Azure Functions

  • 📃 README: CommandQuery.AzureFunctions.md
  • 💁 Samples:
    • CommandQuery.Sample.AzureFunctions.V3
    • CommandQuery.Sample.AzureFunctions.V3.Tests
    • CommandQuery.Sample.AzureFunctions.V5
    • CommandQuery.Sample.AzureFunctions.V5.Tests

CommandQuery.GoogleCloudFunctions ⚡

NuGet NuGet

Command Query Separation for Google Cloud Functions

  • 📃 README: CommandQuery.GoogleCloudFunctions.md
  • 💁 Samples:
    • CommandQuery.Sample.GoogleCloudFunctions
    • CommandQuery.Sample.GoogleCloudFunctions.Tests

CommandQuery.Client 🧰

NuGet NuGet

Clients for CommandQuery APIs

  • 📃 README: CommandQuery.Client.md
  • 💁 Samples:
    • CommandQuery.Sample.Client

CommandQuery.AspNet.WebApi 🌐

NuGet NuGet

Command Query Separation for ASP.NET Web API 2

⛔ This package is no longer maintained and new versions will not be published

  • 📃 README: CommandQuery.AspNet.WebApi.md
  • 💁 Samples:
    • CommandQuery.Sample.AspNet.WebApi
    • CommandQuery.Sample.AspNet.WebApi.Tests

Upgrading

⬆️ Upgrading from version 1.0.0 to 2.0.0

Upgrade command/query handlers:

  • Upgrade the project target framework from ~~net461~~ to netstandard2.0 or greater
  • Add a CancellationToken parameter to the HandleAsync methods in classes that implement ICommandHandler<TCommand>, ICommandHandler<TCommand, TResult> and IQueryHandler<TQuery, TResult>

Upgrade AspNet.WebApi:

  • Migrate from CommandQuery.AspNet.WebApi to CommandQuery.AspNetCore

Upgrade AspNetCore:

  • Consider to upgrade the project target framework to netcoreapp3.1 or net5.0
  • Consider to use the extension methods AddCommandControllers and AddQueryControllers in Startup.cs

Upgrade AWSLambda:

  • Upgrade the project target framework to netcoreapp3.1
  • Change the method invocation on CommandFunction and QueryFunction from ~~Handle~~ to HandleAsync
  • Change the argument on HandleAsync methods from ~~ILambdaContext~~ to ILambdaLogger
  • Consider to use the extension methods AddCommandFunction and AddQueryFunction on IServiceCollection
  • Consider to use the JsonSerializerOptions constructor argument in CommandFunction and QueryFunction to configure JSON serialization/deserialization

Upgrade AzureFunctions:

  • Upgrade the project target framework to netcoreapp3.1 or net5.0
  • Change the method invocation on CommandFunction and QueryFunction from ~~Handle~~ to HandleAsync
  • Consider to use the extension methods AddCommandControllers and AddQueryControllers in Startup.cs/Program.cs
  • Consider to use the CancellationToken argument on HandleAsync methods in netcoreapp3.1 projects
  • Consider to use the JsonSerializerSettings/JsonSerializerOptions constructor argument in CommandFunction and QueryFunction to configure JSON serialization/deserialization

Upgrade Client:

  • Change the method invocation on CommandClient and QueryClient from ~~Post~~ to PostAsync and from ~~Get~~ to GetAsync
  • Consider to use the AddHttpClient extension method on IServiceCollection to create the CommandClient and QueryClient (see sample)
  • Consider to use the CancellationToken argument to methods in CommandClient and QueryClient

Validation:

  • Consider to use the AssertConfigurationIsValid method on CommandProcessor and QueryProcessor to validate handler and type configuration

Acknowledgements

Inspired by Steven van Deursen blog posts:

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Metadata

Command Query Separation for 🌐ASP.NET Core ⚡AWS Lambda ⚡Azure Functions ⚡Google Cloud Functions

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