Elsa 2.0 为什么这个工作流执行一个分叉的两个分支，而我只期望一个分支？

Question

Elsa 正在执行工作流的两个分支，而我只期望一个分支，A 或 B。这是控制台应用程序的文件。

为了您的方便，我推送了 same here as well。

class Program
{
    static async Task Main(string[] args)
    {
        var services = new ServiceCollection()
            .AddElsa(options => options
                .AddConsoleActivities()
                .AddActivity<ForkBranchDecisionActivity>()
                .AddWorkflow<SimpleForkWorkflow>())
            .BuildServiceProvider();

        var workflowStarter = services.GetRequiredService<IBuildsAndStartsWorkflow>();

        await workflowStarter.BuildAndStartWorkflowAsync<SimpleForkWorkflow>();
        Console.WriteLine("Done. Good bye");
    }
}

当我输入 'A' 时，结果将是 'A'，否则将是 'B'。

public class ForkBranchDecisionActivity : Activity
{
    protected override IActivityExecutionResult OnExecute()
    {
        Console.WriteLine("Choose a branch. A or B");
        Console.WriteLine("Typing a will resulting in going through branch A");
        Console.WriteLine("Any other key will result in branch B");
        var userChoosenBranch = Console.ReadLine();

        if (userChoosenBranch!.ToUpper() == "A")
            return Outcome("A");
        
        return Outcome("B");
    }
}

选择分支不是根据之前activity的结果吗？如果不是那么什么决定了要执行的分支？为什么在我的案例中执行了两个分支？

public class SimpleForkWorkflow : IWorkflow
{
    public void Build(IWorkflowBuilder builder)
    {
        builder
            .WriteLine("This demonistrates a simple workflow with fork .")
            .WriteLine("Using forks we can branch a workflow.")
            .Then<ForkBranchDecisionActivity>()
            .Then<Fork>(
                fork => fork.WithBranches("A", "B"),
                fork =>
                {
                    var aBranch = fork
                        .When("A")
                        .WriteLine("You are in A branch. First line")
                        .WriteLine("You are in A branch. Second line.")
                        .ThenNamed("AfterJoin");

                    var bBranch = fork
                        .When("B")
                        .WriteLine("You are in B branch. First line")
                        .WriteLine("You are in B branch. Second line.")
                        .ThenNamed("AfterJoin");
                })
            .WithName("AB Fork")
            .Add<Join>(x => x.WithMode(Join.JoinMode.WaitAny)).WithName("AfterJoin")
            .WriteLine("Workflow finished.");
    }
}

我的最终控制台输出如下所示。

This demonistrates a simple workflow with fork .
Using forks we can branch a workflow.
Choose a branch. A or B
Typing a will resulting in going through branch A
Any other key will result in branch B
a
You are in B branch. First line
You are in B branch. Second line.
Workflow finished.
You are in A branch. First line
You are in A branch. Second line.
Workflow finished.
Done. Good bye

更新

谢谢@Sipke Schoorstra。乍一看并不明显。所以在这里突出显示更改。

而不是

        .Then<ForkBranchDecisionActivity>()
        .Then<Fork>(

应该是

        .Then<ForkBranchDecisionActivity>(fork =>
        {
            fork.When("A")

Note Fork activity 已完全删除，不再是工作流程的一部分。

Answer 1

这是设计使然：Fork activity 将安排所有分支。这是一种将工作流执行拆分为多个分支的方法。

这允许您做一些事情，比如在一个分支中等待一些用户输入，但在某个超时事件后继续另一个分支。这种情况的一个很好的例子是 described here.

要实施您的工作流程，您只需要：

public class SimpleForkWorkflow : IWorkflow
{
    public void Build(IWorkflowBuilder builder)
    {
        builder
            .WriteLine("This demonstrates a simple workflow with switch.")
            .WriteLine("Using switch we can branch a workflow.")
            .Then<ForkBranchDecisionActivity>(fork =>
            {
                fork.When("A")
                    .WriteLine("You are in A branch. First line")
                    .WriteLine("You are in A branch. Second line.")
                    .ThenNamed("Finish");

                fork.When("B")
                    .WriteLine("You are in B branch. First line")
                    .WriteLine("You are in B branch. Second line.")
                    .ThenNamed("Finish");
                
            })
            .WriteLine("Workflow finished.").WithName("Finish");
    }
}

请注意，Then<ForkBranchDecisionActivity> 调用接受一个参数，允许您将任意结果连接到您的 activity（在您的情况下为“A”和“B”）。

当您运行此工作流程时，结果将如预期：

This demonstrates a simple workflow with switch.
Using switch we can branch a workflow.
Choose a branch. A or B
Typing 'a' will result in going through branch A
Any other key will result in branch B
a
You are in A branch. First line
You are in A branch. Second line.
Workflow finished.

Elsa 2.0 为什么这个工作流执行一个分叉的两个分支，而我只期望一个分支？

Elsa 2.0 Why is this workflow executing both the branches of a fork, when I am expecting only one?

elsa-workflows

更新