最近工作需要，在调研BMP产品（开源和商用），重点了解了activiti和它的商业产品Alfresco Process Services，这是java的体系，成熟，完善(三方开源库是java多年开源积累下的最宝贵的财富)，出身.neter的我自然就想看看.net世界里有没有类似的产品。于是就找到两篇关于elsa的文章，一篇是善友兄的《推荐一个很棒的开源工作流elsa-core》，另一篇国庆兄的《.NET 5 开源工作流框架elsa技术研究》，于是还专门致电国庆兄了解elsa这个开源框架的状况，国庆兄很细致的给我作了分享和演示（为开源精神，分享精神点赞），感谢。

于是我也小试一把elsa，同时也把自己的小心得分享出来.

demo的思路很简单，就是从一个api中请求信息，显示出来，这里用到两个activity：一个SendHttpRequest，一个Writeline。

定义webapi服务：

namespace APIDemo.Controllers
{[ApiController][Route("[controller]")]public class HomeController : ControllerBase{private readonly ILogger<HomeController> _logger;public HomeController(ILogger<HomeController> logger){_logger = logger;}[HttpGet]public Person GetPerson(){_logger.LogInformation("请求person");return new Person() { ID = 100, Name = "张三丰收", Age = 22, Sex = true };}}public class Person{public int ID { get; set; }public string Name { get; set; }public int Age { get; set; }public bool Sex { get; set; }}
}

定义elsa工作流：

using Elsa.Activities.Console.Activities;
using Elsa.Activities.Http.Activities;
using Elsa.Activities.Http.Parsers;
using Elsa.Activities.Http.Services;
using Elsa.Expressions;
using Elsa.Scripting.JavaScript;
using Elsa.Services;
using Elsa.Services.Models;
using Microsoft.Extensions.DependencyInjection;
using System;
using System.Threading.Tasks;namespace Elsa01
{class Program{async static Task Main(string[] args){Console.WriteLine("回车开始");Console.ReadLine();var services = new ServiceCollection().AddElsa()//注入Response返回格式.AddScoped<IHttpResponseBodyParser, JsonHttpResponseBodyParser>()//注入httpclient工厂.AddHttpClient().AddActivity<SendHttpRequest>().AddActivity<WriteLine>().BuildServiceProvider();var invoker = services.GetService<IWorkflowInvoker>();await invoker.StartAsync<PersonHandleWorkflow>();Console.WriteLine("回车结束");Console.ReadLine();}}/// <summary>/// 定义工作流两个activity,一个是请求webapi，一个是显示请求结果/// </summary>public class PersonHandleWorkflow : IWorkflow{public void Build(IWorkflowBuilder builder){builder.StartWith<SendHttpRequest>(RequestAPI, "http5001").Then<WriteLine>(ShowMessage);}void ShowMessage(WriteLine write){//用javascript脚本来处理返回信息write.TextExpression = new JavaScriptExpression<string>("'ID:'+lastResult('http5001').Content[\"id\"]+'  Name:'+lastResult('http5001').Content[\"name\"]+'  Age:'+lastResult('http5001').Content[\"age\"]");}void RequestAPI(SendHttpRequest http){//定义http发送参数http.ContentType = "application/json";http.Method = "get";http.Url = new WorkflowExpression<Uri>(LiteralEvaluator.SyntaxName, "https://localhost:5001/home");}}
}