CQRS and Mediator Scaffolding

Medium article

CQRS & Mediator Part 2: Domain scaffolding with Roslyn API and Dotnet CLI in this part we will be building a dotnet CLI tool which follows the CQRS and Mediator patterns to auto generate commands, queries, responses and handlers in the domain layer using Roslyn API for code generation.

Installation

Install using dotnet cli:

dotnet tool install --global CQRSAndMediator.Scaffolding

To uninstall use:

dotnet tool uninstall cqrsandmediator.scaffolding --global

Breakdown of concepts and commands

Show help information:

scaffold -h

Create a new solution

scaffold new sln -n <NAME>

Creates a new solution along with the class libraries, Nunit projects, setup dependencies and install nuget packages

Create new Mediator handlers

scaffold new domain -c <CONCERN> -o <OPERATION> -ot <OPERATION TYPE>

Example of a new Create Orders handler

New Solution

Preview of a newly created solution:

Command Parameters:

Concern: Name of the domain area you are working in i.e Orders, People, Invoice ect.

-c|--concern <NAME>

Operation: Name of the action you are taking in your concern i.e GetById, GetPagedResult for queries or Create, Patch, Update for commands.

-o|--operation <OPERATION>

OperationType: The type of CQRS operation you are scaffolding i.e command or query

-ot|--operationtype <TYPE>

GroupBy: Specify how to group the domain actions. Either by concern or operation: Group domain objects by [C] for concerns or [O] for operations, defaults to concerns

-g|--groupBy <TYPE>

By concern: i.e group by concern when parameters are -c Orders -o GetById -ot query

| YourDomainLayer
    | Orders
        | Handlers
            | OrdersGetByIdHandler.cs
        | Responses
            | OrdersGetByIdResponse.cs
        | Queries
            | OrderGetByIdQuery.cs

By operation i.e group by operation when parameters are -c Orders -o GetById -ot query -g O

| YourDomainLayer
    | Handler
        | OrdersGetByIdHandler.cs
    | Responses
        | OrdersGetByIdResponse.cs
    | Queries
        | OrderGetByIdQuery.cs

Usage

Note: The tool requires that the project is setup already and that the actions are executed in the top level directory of where your domain layer directory is located.

Use case scaffold out the CRUD domain for an invoice:

The Create Command

scaffold new domain -c Invoices -o Create -ot command

The Get By id query

scaffold new domain -c Invoices -o GetById -ot query

The Patch Command

scaffold new domain -c Invoices -o Patch -ot command

Develop locally

Update the nuget package version located in CQRSAndMediator.Scaffolding.csproj

dotnet build .
dotnet pack

then in the solution directory:

dotnet tool update -g cqrsandmediator.scaffolding --add-source ./nupkg --version x.x.x