Introduction

FlowR is a .NET Standard 2.0 framework for building in-process flows based on a series of decoupled exchanges. It leverages the MediatR framework and dependency injection to enable flows to be defined declaratively using a fluent API.

Fluent API

The following example gives a flavour of how a flow is defined using the fluent API.

A flow is made up of a sequence of activity and decision steps. Activities perform processing, whilst decisions control the path through the flow.

    public class MyFlowHandler : FlowHandler<MyFlowRequest, MyFlowResponse>
    {
        public MyFlowHandler(IMediator mediator) : base(mediator)
        {
        }

        protected override void ConfigureDefinition(
            FlowDefinition<MyFlowRequest, MyFlowResponse> flowDefinition)
        {
            flowDefinition

                .Do("Activity1", 
                    new FlowActivityDefinition<Activity1Request, Activity1Response>())
                
                .Check("FlowValue", 
                    new FlowDecisionDefinition<FlowValueDecision<string>, string>()
                        .BindInput(req => req.SwitchValue, "FlowValue"))
                .When("2").Goto("Activity2")
                .Else().Goto("Activity3")

                .Do("Activity2", 
                    new FlowActivityDefinition<Activity2Request, Activity2Response>())
                .End()

                .Do("Activity3", 
                    new FlowActivityDefinition<Activity3Request, Activity3Response>());
        }
    }

Visualisation

FlowR can visualise the defined flows in DOT graph description language, which can be rendered by many open source packages. For example, the image below was generated from the Twenty Questions sample:

Samples

There are a number of sample projects that demonstrate the features of FlowR

• Hello FlowR - A console application that demonstrates a simple flow containing a single activity that combines design-time and run-time values to say hello.

• Twenty Questions - A console application that demonstrates a multi-branch flow, how it can be tested and how it can be visualised.

• Business Example is a web API that makes loan decisions based using a process implemented using FlowR. It demonstrates the following features of FlowR:

  • Flow logic can be tested in isolation
  • Activities can be tested in isolation
  • Flows can be visualised
  • Flows have comprehensive logging by default