SampleDocumentApprovalWorkflow.cs

using System;
using WorkflowEngine.Workflow;
using WorkflowEngine.Workflow.Nodes;
using WorkflowEngine.Workflow.Transitions;
using static WorkflowEngine.SampleDocumentApprovalWorkflowContext;

namespace WorkflowEngine
{
    public class SampleDocumentApprovalWorkflow: Workflow.Workflow
    {
        class DoApprovalNode: ActionNode
        {
            public DoApprovalNode(WorkflowContext context, string name): base(context, name, TYPE.ACTION_NODE)
            {
            }

            public override void Execute()
            {
                Console.WriteLine("Please enter 'approve' or 'decline'.");
                
                string decision = Console.ReadLine().ToLower();
                if (decision != "approve" && decision != "decline")
                {
                    Execute();
                    return;
                }

                context.SetValueForProperty("Decision", decision);
            }
        }

        class PostApprovalNode: MultiStepNode
        {
            public PostApprovalNode(WorkflowContext context, string name): base(context, name, TYPE.ACTION_NODE)
            {
                AddStep((context) =>
                {
                    Console.WriteLine("Executing step 1.");
                    Console.WriteLine("Your decision: " + context.GetValueForProperty<string>("Decision"));
                });

                AddStep((context) => 
                {
                    Console.WriteLine("Executing step 2.");
                });
            }
        }

        public SampleDocumentApprovalWorkflow()
        {
            context = new SampleDocumentApprovalWorkflowContext();
            var startNode = new StartNode(context, "BEGIN");
            var approvalNode = new DoApprovalNode(context, "IN_APPROVAL");
            var postApprovalNode = new PostApprovalNode(context, "POST_APPROVAL");
            var finalNode = new EndNode(context, "FINISHED");

            Initialize(startNode);

            AddTransition(startNode, approvalNode,
                () =>
                {
                    var currentContext = context as SampleDocumentApprovalWorkflowContext;
                    if (currentContext == null)
                    {
                        return false;
                    }
                    
                    return currentContext.ApprovalState == APPROVAL_STATE.UNAPPROVED;
                },
                () =>
                {
                    Console.WriteLine("Going forward to approval state.");
                    Console.WriteLine("Sent e-mail to manager.");

                    context.SetValueForProperty<APPROVAL_STATE>("ApprovalState", APPROVAL_STATE.IN_PROGRESS);
                }
            );

            AddTransition(approvalNode, postApprovalNode,
                () => 
                {
                    string decision = context.GetValueForProperty<string>("Decision");
                    var state = context.GetValueForProperty<APPROVAL_STATE>("ApprovalState");

                    return decision == "approve" && state == APPROVAL_STATE.IN_PROGRESS;
                },
                () =>
                {
                    Console.WriteLine("Finishing approval workflow.");
                }
            );

            AddTransition(postApprovalNode, finalNode,
                () => true,
                () =>
                {
                    context.SetValueForProperty<APPROVAL_STATE>("ApprovalState", APPROVAL_STATE.APPROVED);
                }
            );

            AddTransition(approvalNode, startNode, 
                () => 
                {
                    string decision = context.GetValueForProperty<string>("Decision");
                    var state = context.GetValueForProperty<APPROVAL_STATE>("ApprovalState");

                    return decision == "decline" && state == APPROVAL_STATE.IN_PROGRESS;
                }, 
                () =>
                {
                    context.SetValueForProperty<string>("Decision", null);
                    context.SetValueForProperty<APPROVAL_STATE>("ApprovalState", APPROVAL_STATE.UNAPPROVED);

                    Console.WriteLine("Moving back to initial state.");
                }
            );
        }
    }
}