ActivityName as expression. It solves #542 issue.

Author: alimozdemir

WorkflowCore.sln

@@ -152,6 +152,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "WorkflowCore.Sample19", "sr
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "WorkflowCore.Persistence.RavenDB", "src\providers\WorkflowCore.Persistence.RavenDB\WorkflowCore.Persistence.RavenDB.csproj", "{AF205715-C8B7-42EF-BF14-AFC9E7F27242}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "WorkflowCore.Sample20", "src\samples\WorkflowCore.Sample20\WorkflowCore.Sample20.csproj", "{68D1B955-1049-477B-A894-13FCB96C45DE}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -374,6 +376,10 @@ Global
 		{AF205715-C8B7-42EF-BF14-AFC9E7F27242}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{AF205715-C8B7-42EF-BF14-AFC9E7F27242}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{AF205715-C8B7-42EF-BF14-AFC9E7F27242}.Release|Any CPU.Build.0 = Release|Any CPU
+		{68D1B955-1049-477B-A894-13FCB96C45DE}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{68D1B955-1049-477B-A894-13FCB96C45DE}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{68D1B955-1049-477B-A894-13FCB96C45DE}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{68D1B955-1049-477B-A894-13FCB96C45DE}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -436,6 +442,7 @@ Global
 		{54DE20BA-EBA7-4BF0-9BD9-F03766849716} = {E6CEAD8D-F565-471E-A0DC-676F54EAEDEB}
 		{1223ED47-3E5E-4960-B70D-DFAF550F6666} = {5080DB09-CBE8-4C45-9957-C3BB7651755E}
 		{AF205715-C8B7-42EF-BF14-AFC9E7F27242} = {2EEE6ABD-EE9B-473F-AF2D-6DABB85D7BA2}
+		{68D1B955-1049-477B-A894-13FCB96C45DE} = {5080DB09-CBE8-4C45-9957-C3BB7651755E}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {DC0FA8D3-6449-4FDA-BB46-ECF58FAD23B4}

src/WorkflowCore/Interface/IWorkflowModifier.cs

@@ -152,5 +152,15 @@ IContainerStepBuilder<TData, Recur, TStepBody> Recur(Expression<Func<TData, Time
     IStepBuilder<TData, Activity> Activity(string activityName, Expression<Func<TData, object>> parameters = null,
         Expression<Func<TData, DateTime>> effectiveDate = null, Expression<Func<TData, bool>> cancelCondition = null);
 
+    /// <summary>
+    /// Wait here until an external activity is complete
+    /// </summary>
+    /// <param name="activityName">The name used to identify the activity to wait for</param>
+    /// <param name="parameters">The data to pass the external activity worker</param>
+    /// <param name="effectiveDate">Listen for events as of this effective date</param>
+    /// <param name="cancelCondition">A conditon that when true will cancel this WaitFor</param>
+    /// <returns></returns>
+    IStepBuilder<TData, Activity> Activity(Expression<Func<TData, IStepExecutionContext, string>> activityName, Expression<Func<TData, object>> parameters = null,
+        Expression<Func<TData, DateTime>> effectiveDate = null, Expression<Func<TData, bool>> cancelCondition = null);
     }
 }

src/WorkflowCore/Services/FluentBuilders/StepBuilder.cs

@@ -522,5 +522,24 @@ public IStepBuilder<TData, Activity> Activity(string activityName, Expression<Fu
             Step.Outcomes.Add(new ValueOutcome { NextStep = newStep.Id });
             return stepBuilder;
         }
+
+        public IStepBuilder<TData, Activity> Activity(Expression<Func<TData, IStepExecutionContext, string>> activityName, Expression<Func<TData, object>> parameters = null, Expression<Func<TData, DateTime>> effectiveDate = null, Expression<Func<TData, bool>> cancelCondition = null)
+        {
+            var newStep = new WorkflowStep<Activity>();
+            newStep.CancelCondition = cancelCondition;
+
+            WorkflowBuilder.AddStep(newStep);
+            var stepBuilder = new StepBuilder<TData, Activity>(WorkflowBuilder, newStep);
+            stepBuilder.Input((step) => step.ActivityName, activityName);
+
+            if (parameters != null)
+                stepBuilder.Input((step) => step.Parameters, parameters);
+
+            if (effectiveDate != null)
+                stepBuilder.Input((step) => step.EffectiveDate, effectiveDate);
+
+            Step.Outcomes.Add(new ValueOutcome { NextStep = newStep.Id });
+            return stepBuilder;
+        }
     }
 }

src/WorkflowCore/Services/FluentBuilders/WorkflowBuilder.cs

@@ -271,6 +271,10 @@ public IStepBuilder<TData, Activity> Activity(string activityName, Expression<Fu
         {
             return Start().Activity(activityName, parameters, effectiveDate, cancelCondition);
         }
+        public IStepBuilder<TData, Activity> Activity(Expression<Func<TData, IStepExecutionContext, string>> activityName, Expression<Func<TData, object>> parameters = null, Expression<Func<TData, DateTime>> effectiveDate = null, Expression<Func<TData, bool>> cancelCondition = null)
+        {
+            return Start().Activity(activityName, parameters, effectiveDate, cancelCondition);
+        }
 
         private IStepBuilder<TData, InlineStepBody> Start()
         {

src/samples/WorkflowCore.Sample20/ActivityWorkflow.cs

@@ -0,0 +1,29 @@
+using System;
+using WorkflowCore.Interface;
+using WorkflowCore.Sample20.Steps;
+
+namespace WorkflowCore.Sample20
+{
+    class ActivityWorkflow : IWorkflow<MyData>
+    {
+        public string Id => "activity-sample";
+        public int Version => 1;
+
+        public void Build(IWorkflowBuilder<MyData> builder)
+        {
+            builder
+                .StartWith<HelloWorld>()
+                .Activity((data, context) => "get-approval-" + context.Workflow.Id, (data) => data.Request)
+                    .Output(data => data.ApprovedBy, step => step.Result)
+                .Then<CustomMessage>()
+                    .Input(step => step.Message, data => "Approved by " + data.ApprovedBy)
+                .Then<GoodbyeWorld>();
+        }
+    }
+
+    class MyData
+    {
+        public string Request { get; set; }
+        public string ApprovedBy { get; set; }
+    }
+}

src/samples/WorkflowCore.Sample20/Program.cs

@@ -0,0 +1,53 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using System;
+using WorkflowCore.Interface;
+
+namespace WorkflowCore.Sample20
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            var serviceProvider = ConfigureServices();
+
+            //start the workflow host
+            var host = serviceProvider.GetService<IWorkflowHost>();
+            host.RegisterWorkflow<ActivityWorkflow, MyData>();
+            host.Start();
+
+            Console.WriteLine("Starting workflow...");
+
+            var workflowId = host.StartWorkflow("activity-sample", new MyData { Request = "Spend $1,000,000" }).Result;
+
+            var approval = host.GetPendingActivity("get-approval-" + workflowId, "worker1", TimeSpan.FromMinutes(1)).Result;
+
+            if (approval != null)
+            {                
+                Console.WriteLine("Approval required for " + approval.Parameters);
+                host.SubmitActivitySuccess(approval.Token, "John Smith");
+            }
+
+            Console.ReadLine();
+            host.Stop();
+        }
+
+        private static IServiceProvider ConfigureServices()
+        {
+            //setup dependency injection
+            IServiceCollection services = new ServiceCollection();
+            //services.AddWorkflow();
+            services.AddWorkflow(x => x.UseMongoDB(@"mongodb://localhost:27017", "workflow"));
+            //services.AddWorkflow(x => x.UseSqlServer(@"Server=.;Database=WorkflowCore;Trusted_Connection=True;", true, true));
+            //services.AddWorkflow(x => x.UsePostgreSQL(@"Server=127.0.0.1;Port=5432;Database=workflow;User Id=postgres;", true, true));
+            services.AddLogging(cfg => 
+            {
+                cfg.AddConsole();
+                cfg.AddDebug();
+            });
+
+            var serviceProvider = services.BuildServiceProvider();
+            return serviceProvider;
+        }
+    }
+}

src/samples/WorkflowCore.Sample20/README.md

@@ -0,0 +1,34 @@
+# Activity sample
+
+Illustrates how to have your workflow wait for an external activity that is fulfilled by a worker that you implement.
+
+This workflow will wait for the `get-approval-{workflowId}`  activity and pass the request string to it as an input.
+
+The main reason behind of this example is Activities are global listeners. Therefore, in some cases, you want to be sure about its uniqueness.
+
+Also, you can take look the issue https://github.com/danielgerlag/workflow-core/issues/542
+
+```c#
+builder
+    .StartWith<HelloWorld>()
+    .Activity((data, context) => context.Workflow.Id, (data) => data.Request)
+        .Output(data => data.ApprovedBy, step => step.Result)
+    .Then<CustomMessage>()
+        .Input(step => step.Message, data => "Approved by " + data.ApprovedBy)
+    .Then<GoodbyeWorld>();
+```
+
+Then we implement an activity worker to pull pending activities of type `get-approval`, where we can inspect the input and submit a response back to the waiting workflow.
+
+```c#
+var workflowId = host.StartWorkflow("activity-sample", new MyData { Request = "Spend $1,000,000" }).Result;
+
+var approval = host.GetPendingActivity("get-approval-" + workflowId, "worker1", TimeSpan.FromMinutes(1)).Result;
+
+if (approval != null)
+{                
+    Console.WriteLine("Approval required for " + approval.Parameters);
+    host.SubmitActivitySuccess(approval.Token, "John Smith");
+}
+```
+

src/samples/WorkflowCore.Sample20/Steps/CustomMessage.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Linq;
+using WorkflowCore.Interface;
+using WorkflowCore.Models;
+
+namespace WorkflowCore.Sample20.Steps
+{
+    public class CustomMessage : StepBody
+    {
+        
+        public string Message { get; set; }
+
+        public override ExecutionResult Run(IStepExecutionContext context)
+        {
+            Console.WriteLine(Message);
+            return ExecutionResult.Next();
+        }
+    }
+}

src/samples/WorkflowCore.Sample20/Steps/GoodbyeWorld.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Linq;
+using WorkflowCore.Interface;
+using WorkflowCore.Models;
+
+namespace WorkflowCore.Sample20.Steps
+{
+    public class GoodbyeWorld : StepBody
+    {
+        public override ExecutionResult Run(IStepExecutionContext context)
+        {
+            Console.WriteLine("Goodbye world");
+            return ExecutionResult.Next();
+        }
+    }
+}

src/samples/WorkflowCore.Sample20/Steps/HelloWorld.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Linq;
+using WorkflowCore.Interface;
+using WorkflowCore.Models;
+
+namespace WorkflowCore.Sample20.Steps
+{
+    public class HelloWorld : StepBody
+    {
+        public override ExecutionResult Run(IStepExecutionContext context)
+        {
+            Console.WriteLine("Hello world");
+            return ExecutionResult.Next();
+        }
+    }
+}