前言

1.什么是工作流

工作流是OA系统比较重要的功能之一，主要在于企业流程协同审批，有效进行流程管理。

流程管理起源于生产组织和办公自动化领域，是针对日常工作中具有固定程序的活动提出的一个概念。目的是通过将工作分解成定义良好的任务、角色，按照一定的规则和过程来执行这些任务并对它们进行监控，达到提高办事效率、降低生产成本、提高企业生产经营管理水平和企业竞争力的目标。

现代计算机技术实现了工作流，是支持企业经营过程高效执行并监控其执行过程的计算机软件系统。工作流软件类似电脑桌面操作系统，操作系统驱动电脑各部件协同运转，工作流软件则驱动业务过程自动有序进行。

Workflow-Core地址：https://github.com/danielgerlag/workflow-core

一、Workflow-Core轻量级工作流引擎

1.安装包

Install-Package WorkflowCore
Microsoft.Extensions.Logging
Microsoft.Extensions.Logging.Debug

2.随机流程

2.1 定义步骤

1、步骤一

using System;
using System.Linq;
using WorkflowCore.Interface;
using WorkflowCore.Models;

namespace WorkflowCore.Sample01.Steps
{
    public class HelloWorld : StepBody
    {
        public override ExecutionResult Run(IStepExecutionContext context)
        {
            Console.WriteLine("Hello world");
            return ExecutionResult.Next();
        }
    }
}

2、步骤二

public class RandomOutput : StepBody
{        
    public override ExecutionResult Run(IStepExecutionContext context)
    {
        Random rnd = new Random();
        int value = rnd.Next(2);
        Console.WriteLine("Generated random value {0}", value);
        return ExecutionResult.Outcome(value);
    }
}

3、随机步骤

public class CustomMessage : StepBody
{
    
    public string Message { get; set; }

    public override ExecutionResult Run(IStepExecutionContext context)
    {
        Console.WriteLine(Message);
        return ExecutionResult.Next();
    }
}

public class GoodbyeWorld : StepBody
{
    public override ExecutionResult Run(IStepExecutionContext context)
    {
        Console.WriteLine("Goodbye world");
        return ExecutionResult.Next();
    }
}

2.2 定义工作流

public class SimpleDecisionWorkflow : IWorkflow
{
    public string Id => "Simple Decision Workflow";

    public int Version => 1;

    public void Build(IWorkflowBuilder<object> builder)
    {
        builder
            .StartWith<HelloWorld>()
            .Then<RandomOutput>(randomOutput =>
            {
                randomOutput
                    .When(0)
                        .Then<CustomMessage>(cm =>
                        {
                            cm.Name("Print custom message");
                            cm.Input(step => step.Message, data => "Looping back....");
                        })
                        .Then(randomOutput);  //loop back to randomOutput

                randomOutput
                    .When(1)
                        .Then<GoodbyeWorld>();
            });
    }
}

2.3 启动工作流

using Microsoft.Extensions.DependencyInjection;
using WorkflowCore.Interface;
using WorkflowCore.Sample02;

IServiceProvider serviceProvider = ConfigureServices();

//start the workflow host
var host = serviceProvider.GetService<IWorkflowHost>();
host.RegisterWorkflow<SimpleDecisionWorkflow>();
host.Start();

host.StartWorkflow("Simple Decision Workflow");

Console.ReadLine();
host.Stop();

static IServiceProvider ConfigureServices()
{
    //setup dependency injection
    IServiceCollection services = new ServiceCollection();
    services.AddLogging();
    services.AddWorkflow();
    var serviceProvider = services.BuildServiceProvider();

    return serviceProvider;
}

2.4 运行

可以看见直接结束，让我们再次运行

这次运行发送三次消息才结束

二、Workflow-Core的流程配置

1.代码配置

public class MyWorkflow : IWorkflow
{
    public void Build(IWorkflowBuilder<MyData> builder)
    {    
        builder
           .StartWith<Task1>()
           .Then<Task2>()
           .Then<Task3>();
    }
}

2.JSON配置

{
  "Id": "HelloWorld",
  "Version": 1,
  "Steps": [
    {
      "Id": "Hello",
      "StepType": "MyApp.HelloWorld, MyApp",
      "NextStepId": "Bye"
    },        
    {
      "Id": "Bye",
      "StepType": "MyApp.GoodbyeWorld, MyApp"
    }
  ]
}

3.YAML配置

Id: HelloWorld
Version: 1
Steps:
- Id: Hello
  StepType: MyApp.HelloWorld, MyApp
  NextStepId: Bye
- Id: Bye
  StepType: MyApp.GoodbyeWorld, MyApp