前面已经讨论过，Workflow Core的流程与主流程不在同一进程运行，如果我们需要知道流程的运行状态，需要使用OnLifeCycleEvent事件，当流程启动和结束、流程步骤开始和结束时，会触发这个事件。我们可以在这个事件中判断相关流程是否结束。下面是一个简单的例子，说明如何使用这个事件。

using Microsoft.Extensions.DependencyInjection;
using System;
using WorkflowCore.Interface;
using WorkflowCore.Services.DefinitionStorage;

namespace WorkflowCoreFrameworkDSL
{
    class Program
    {
        static void Main(string[] args)
        {
            IServiceProvider serviceProvider = ConfigureServices();

            var loader = serviceProvider.GetService<IDefinitionLoader>();

            var json = System.IO.File.ReadAllText("dataflow.json");
            loader.LoadDefinition(json, Deserializers.Json);
            var host = serviceProvider.GetService<IWorkflowHost>();
            host.Start();

            var mybmi = new MyBMI
            {
                Height=1.75M,
                Weight=75
            };
            var workflowid = host.StartWorkflow("BMIFlow", 1, mybmi).Result;


            host.OnLifeCycleEvent += (evt) =>
            {
                if (evt.WorkflowInstanceId == workflowid && evt.ToString() == "WorkflowCore.Models.LifeCycleEvents.WorkflowCompleted")
                {
                    Console.WriteLine(mybmi.Height);
                    Console.WriteLine(mybmi.Weight);
                    Console.WriteLine(mybmi.BMI);
                    Console.WriteLine(mybmi.Status);
                }
            };
            Console.ReadLine();
            host.Stop();
        }

        private static IServiceProvider ConfigureServices()
        {
            //setup dependency injection
            IServiceCollection services = new ServiceCollection();
            services.AddLogging();
            services.AddWorkflow();
            //这是新增加的服务
            services.AddWorkflowDSL();
            var serviceProvider = services.BuildServiceProvider();

            return serviceProvider;
        }
    }
}

这个例子中有两个步骤，分别计算BMI和判断BMI的状态，采用json文件定义流程：

{
  "Id": "BMIFlow",
  "Version": 1,
  "DataType": "WorkflowCoreFrameworkDSL.MyBMI, WorkflowCoreFrameworkDSL",
  "Steps": [
    {
      "Id": "CalBmi",
      "StepType": "WorkflowCoreFrameworkDSL.CalBmi,WorkflowCoreFrameworkDSL",
      "NextStepId": "CalStatus",
      "Inputs": {
        "Height": "data.Height",
        "Weight": "data.Weight"
      },
      "Outputs": {
        "BMI": "step.BMI"
      }
    },
    {
      "Id": "CalStatus",
      "StepType": "WorkflowCoreFrameworkDSL.CalStatus,WorkflowCoreFrameworkDSL",
      "Inputs": {
        "BMI": "data.BMI"
      },
      "Outputs": {
        "Status": "step.Status"
      }
    }
  ]
}

两个Step的代码如下：

using WorkflowCore.Interface;
using WorkflowCore.Models;

namespace WorkflowCoreFrameworkDSL
{
    public class CalBmi : StepBody
    {
        public decimal Height { get; set; }

        public decimal Weight { get; set; }

        public decimal BMI { get; set; }

        public override ExecutionResult Run(IStepExecutionContext context)
        {
            BMI=Weight/Height/Height;
            return ExecutionResult.Next();
        }
    }

    public class CalStatus : StepBody
    {
        
        public decimal BMI { get; set; }

        public string Status { get; set; }

        public override ExecutionResult Run(IStepExecutionContext context)
        {
            if (BMI < 18) Status = "偏瘦";
            else if (BMI < 24) Status = "正常";
            else if (BMI < 28) Status = "超重";
            else Status = "肥胖";
                return ExecutionResult.Next();
        }
    }
}