C#工作流WorkflowCore學習：Hello World

為什么需要工作流？在之前博文.Net依賴注入技術學習：基本模型中，有提到這個世界的基本構型是縱向分層和橫向組合，而工作流模型在縱向上比源碼級別提升了一個層次，它的基本操作單元是步驟；在橫向上通過一些規則，可以使步驟靈活組合。實現了更高層次抽象的簡潔性和表達力的平衡。

本文介紹了.Net體系比較優秀的開源工作流WorkflowCore，github地址：https://github.com/danielgerlag/workflow-core。

教程參考：https://workflow-core.readthedocs.io/en/latest/

下面定義了2個步驟：HelloWorld和GoodbyeWorld

    public class HelloWorld : StepBody
    {
        public override ExecutionResult Run(IStepExecutionContext context)
        {
            Console.WriteLine("Hello world");
            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("Goodbye world");
            _logger.LogInformation("Hi there!");
            return ExecutionResult.Next();
        }
    }

然后定義一個工作流：

    public class HelloWorldWorkflow : IWorkflow
    {
        public void Build(IWorkflowBuilder<object> builder)
        {
            builder                
                .StartWith<HelloWorld>()                
                .Then<GoodbyeWorld>();
        }

        public string Id => "HelloWorld";
            
        public int Version => 1;
                 
    }

最后啟動工作流：

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

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

            host.StartWorkflow("HelloWorld");
            
            Console.ReadLine();
            host.Stop();
        }
                
        private static IServiceProvider ConfigureServices()
        {
            //setup dependency injection
            IServiceCollection services = new ServiceCollection();
            services.AddLogging();
            services.AddWorkflow();
            //services.AddWorkflow(x => x.UseMongoDB(@"mongodb://localhost:27017", "workflow"));
            services.AddTransient<GoodbyeWorld>();
            
            var serviceProvider = services.BuildServiceProvider();

            return serviceProvider;
        }


    }