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最近想做一個OA相關的網站開發，一直都聽說有workflow的東西，之前也斷斷續續學習過 Workflow Foundation 4.0，還是沒有搞明白到底能夠用它做什么

但還是覺得workflow在某種情形下應該可以適用，雖然還沒有答案，網上搜樓了一通，發現一個workflow-core的東西，覺得挺有意思，遂停下來，琢磨一下，現分享與大家。

* 簡介

workflow core的GitHub主頁

https://github.com/danielgerlag/workflow-core

如主頁上介紹的，workflow core作為一個輕量級workflow引擎，可以嵌入到項目中，其底層是用.NET standard 2.0開發，可以用來追蹤長時間運行的任務狀態，功能也比較強大，支持插件形式持久化，和多節點并行處理，貌似很牛。并且目前有給一個 Conductor 項目，就是使用workflow core作為內核的workflow服務器（原來運行workflow，需要單獨的一個服務器啊），Conductor這里就不展開了。workflow core支持fluent語法，寫起來也非常美觀，雖然沒有WF那樣有圖形化的操作界面，但感覺代碼比較干凈。

* 示例1

新建一個項目，指明使用.net framework 4.6.1以上，新建項目后，在Package Manager Console中，安裝workflow core：Install-Package WorkflowCore，安裝這個包會默認安裝一系列的依賴包

可能由于版本的關系，還需要另外安裝兩個包：Microsoft.Extensions.Logging 和 Microsoft.Extensions.Logging.Debug。這樣就可以按照Sample 01開始編寫代碼了

Sample01是一個helloworld，包含了幾部分內容：

1. 構建StepBody，就是workflow中需要執行的內容，每個類繼承自StepBody這個虛擬類，重載ExecutionResult Run(IStepExecutionContext context)，這個函數中完成所需的工作

public class HelloWorld : StepBody    {        private ILogger logger;        public HelloWorld(ILoggerFactory loggerFactory)        {            logger = loggerFactory.CreateLogger<HelloWorld>();        }        public override ExecutionResult Run(IStepExecutionContext context)        {            Console.WriteLine("Hello world, workflow");            logger.LogInformation("Helloworld workflow");            return ExecutionResult.Next();        }    }    public class GoodbyeWorld : StepBody    {        private ILogger logger;        public GoodbyeWorld(ILoggerFactory loggerFactory)        {            logger = loggerFactory.CreateLogger<GoodbyeWorld>();        }        public override ExecutionResult Run(IStepExecutionContext context)        {            Console.WriteLine("Workflow, Goodbye");            logger.LogInformation("Goodbye workflow");            return ExecutionResult.Next();        }    }    public class SleepStep : StepBody    {        private ILogger logger;        public SleepStep(ILoggerFactory loggerFactory)        {            logger = loggerFactory.CreateLogger("SleepStep");        }        public override ExecutionResult Run(IStepExecutionContext context)        {            Thread.Sleep(1000);            logger.LogInformation("Sleeped");            return ExecutionResult.Next();        }    }

2. 構建workflow，實現IWorkflow接口，每個workflow有一個Id和一個Version，標明這個workflow的身份，這里通過兩種方法構建了HelloWorkflow

   public class HelloWorkflow : IWorkflow    {        public string Id => "HelloWorkflow";        public int Version => 1;        public void Build(IWorkflowBuilder<object> builder)        {            builder.StartWith(context =>            {                Console.WriteLine("Hello world");                return ExecutionResult.Next();            })            .Then(context =>            {                Thread.Sleep(500);                Console.WriteLine("sleeped");                return ExecutionResult.Next();            })            .Then(context =>            {                Console.WriteLine("Goodbye world");                return ExecutionResult.Next();            });        }    }    public class HelloWorkflow2 : IWorkflow    {        public string Id => "HelloWorkflow";        public int Version => 2;        public void Build(IWorkflowBuilder<object> builder)        {            builder.StartWith<HelloWorld>()                .Then<SleepStep>()                .Then<GoodbyeWorld>();        }    }

3. 萬事俱備，準備讓workflow運行起來。第一步當然是需要搭建service，Workflow Core通過Injection命名空間的ServiceCollection添加了Workflow相關的服務，對于有參數的StepBody，需要先通過service的AddTransient函數注冊，這樣才能正確的構造對象

/// <summary> /// 配置workflow /// </summary> /// <returns></returns> private IServiceProvider ConfigureServices() {     //setup dependency injection     IServiceCollection services = new ServiceCollection();     services.AddLogging();     services.AddWorkflow();     //services.AddWorkflow(x => x.UseMongoDB(@"mongodb://localhost:27017", "workflow"));     // 這些個構造函數帶參數的，需要添加到transient中     services.AddTransient<HelloWorld>();     services.AddTransient<GoodbyeWorld>();     services.AddTransient<SleepStep>();     var serviceProvider = services.BuildServiceProvider();     //config logging     var loggerFactory = serviceProvider.GetService<ILoggerFactory>();     loggerFactory.AddProvider(new DebugLoggerProvider());     return serviceProvider; }

接下來，啟動workflow 主機，并啟動一次workflow，將整個窗體代碼貼一下，這樣比較清晰

using Microsoft.Extensions.DependencyInjection;using Microsoft.Extensions.Logging;using Microsoft.Extensions.Logging.Console;using Microsoft.Extensions.Logging.Debug;using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.windows;using System.Windows.Controls;using System.Windows.Data;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Imaging;using System.Windows.Navigation;using System.Windows.Shapes;using WorkflowCore.Interface;using WorkflowCore.Services;using WorkFlowCoreTest.MyWorkflow;namespace WorkFlowCoreTest{    /// <summary>    /// Interaction logic for MainWindow.xaml    /// </summary>    public partial class MainWindow : Window    {        IServiceProvider serviceProvider = null;        bool serviceStarted = false;        public MainWindow()        {            InitializeComponent();        }        private void StartWorkflow()        {            if (serviceProvider == null)            {                serviceProvider = ConfigureServices();                var host1 = serviceProvider.GetService<IWorkflowHost>();                host1.RegisterWorkflow<HelloWorkflow>();                host1.RegisterWorkflow<HelloWorkflow2>();            }            var host = serviceProvider.GetService<IWorkflowHost>();            var wd = host.Registry.GetDefinition("HelloWorkflow");            // 如果host啟動了，不能再次啟動，但沒有判斷方法            if (!serviceStarted)            {                host.Start();                serviceStarted = true;            }            // 啟動workflow工作流            host.StartWorkflow("HelloWorkflow", 1, data: null); //            //host.StartWorkflow("HelloWorkflow");//, 2, data: null, 默認會啟用版本高的        }        private void StopWorkflow()        {            var host = serviceProvider.GetService<IWorkflowHost>();            host.Stop();            serviceStarted = false;        }        /// <summary>        /// 配置workflow        /// </summary>        /// <returns></returns>        private IServiceProvider ConfigureServices()        {            //setup dependency injection            IServiceCollection services = new ServiceCollection();            services.AddLogging();            services.AddWorkflow();            //services.AddWorkflow(x => x.UseMongoDB(@"mongodb://localhost:27017", "workflow"));            // 這些個構造函數帶參數的，需要添加到transient中            services.AddTransient<HelloWorld>();            services.AddTransient<GoodbyeWorld>();            services.AddTransient<SleepStep>();            var serviceProvider = services.BuildServiceProvider();            //config logging            var loggerFactory = serviceProvider.GetService<ILoggerFactory>();            loggerFactory.AddProvider(new DebugLoggerProvider());            return serviceProvider;        }        private void startButton_Click(object sender, RoutedEventArgs e)        {            StartWorkflow();        }        private void stopButton_Click(object sender, RoutedEventArgs e)        {            StopWorkflow();        }    }}

就這樣一個簡單的Workflow Core例子就完成了，總體來說，還是很簡單，清晰的。

出處：

https://www.cnblogs.com/keep-study-to-die/p/12001408.html

 

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