Implement activity execution logging (#89)

* Implement activity logging
* Update Calculator example

samples/Sample04/CalculatorWorkflow.cs

@@ -13,13 +13,13 @@ namespace Sample04
         public void Build(IWorkflowBuilder builder)
         {
             builder
-                .StartWith<WriteLine>(x => x.TextExpression = new LiteralExpression("Welcome to Calculator Workflow!"))
-                .Then<WriteLine>(x => x.TextExpression = new LiteralExpression("Enter number 1:"), id: "start")
-                .Then<ReadLine>(x => x.VariableName = "number1")
-                .Then<WriteLine>(x => x.TextExpression = new LiteralExpression("Enter number 2:"))
-                .Then<ReadLine>(x => x.VariableName = "number2")
-                .Then<WriteLine>(x => x.TextExpression = new LiteralExpression("Now enter the operation you wish to apply. Options are: add, subtract, multiply or divide:"))
-                .Then<ReadLine>(x => x.VariableName = "operation")
+                .StartWith<WriteLine>(x => x.TextExpression = new LiteralExpression("Welcome to Calculator Workflow!"), "welcome")
+                .Then<WriteLine>(x => x.TextExpression = new LiteralExpression("Enter number 1:"), id: "enter-first-number-prompt")
+                .Then<ReadLine>(x => x.VariableName = "number1", id: "read-first-number")
+                .Then<WriteLine>(x => x.TextExpression = new LiteralExpression("Enter number 2:"), id: "enter-second-number-prompt")
+                .Then<ReadLine>(x => x.VariableName = "number2", id: "read-second-number")
+                .Then<WriteLine>(x => x.TextExpression = new LiteralExpression("Now enter the operation you wish to apply. Options are: add, subtract, multiply or divide:"), id: "enter-operation-prompt")
+                .Then<ReadLine>(x => x.VariableName = "operation", id: "read-operation")
                 .Then<Switch>(@switch =>
                     {
                         @switch.Expression = new JavaScriptExpression<string>("operation");
@@ -29,40 +29,41 @@ namespace Sample04
                     {
                         @switch
                             .When("add")
-                            .Then<Sum>(SetupOperation)
-                            .Then("showResult");
+                            .Then<Sum>(SetupOperation, id: "perform-sum")
+                            .Then("show-result");
                         
                         @switch
                             .When("subtract")
-                            .Then<Subtract>(SetupOperation)
-                            .Then("showResult");
+                            .Then<Subtract>(SetupOperation, id: "perform-subtract")
+                            .Then("show-result");
                         
                         @switch
                             .When("multiply")
-                            .Then<Multiply>(SetupOperation)
-                            .Then("showResult");
+                            .Then<Multiply>(SetupOperation, id: "perform-multiply")
+                            .Then("show-result");
                         
                         @switch
                             .When("divide")
-                            .Then<Divide>(SetupOperation)
-                            .Then("showResult");
-                    }
+                            .Then<Divide>(SetupOperation, id: "perform-divide")
+                            .Then("show-result");
+                    },
+                    "inspect-selected-operation"
                 )
-                .Add<WriteLine>(x => x.TextExpression = new JavaScriptExpression<string>("`Result: ${result}`"), "showResult")
-                .Then<WriteLine>(x => x.TextExpression = new LiteralExpression("Try again? (y/n)"))
-                .Then<ReadLine>(x => x.VariableName = "retry")
+                .Add<WriteLine>(x => x.TextExpression = new JavaScriptExpression<string>("`Result: ${result}`"), "show-result")
+                .Then<WriteLine>(x => x.TextExpression = new LiteralExpression("Try again? (y/n)"), id: "try-again-prompt")
+                .Then<ReadLine>(x => x.VariableName = "retry", id: "read-try-again")
                 .Then<IfElse>(
                     x => x.ConditionExpression = new JavaScriptExpression<bool>("retry.toLowerCase() === 'y'"),
                     ifElse =>
                     {
                         ifElse
                             .When(OutcomeNames.True)
-                            .Then("start");
+                            .Then("enter-first-number-prompt");
                         
                         ifElse
                             .When(OutcomeNames.False)
-                            .Then<WriteLine>(x => x.TextExpression = new LiteralExpression("Bye!"));
-                    });;
+                            .Then<WriteLine>(x => x.TextExpression = new LiteralExpression("Bye!"), id: "say-good-bye");
+                    }, id: "inspect-retry");
         }
 
         private void SetupOperation(ArithmeticOperation operation)

samples/Sample04/Program.cs

@@ -35,6 +35,11 @@ namespace Sample04
             var invoker = services.GetService<IWorkflowInvoker>();
             await invoker.StartAsync(workflow);
 
+            Console.WriteLine("Workflow has ended. Here are the activities that have executed:");
+            foreach (var logEntry in workflow.ExecutionLog)
+            {
+                Console.WriteLine("{0}: {1}", logEntry.Timestamp, logEntry.ActivityId);
+            }
             Console.ReadLine();
         }
     }

src/core/Elsa.Abstractions/Services/IWorkflowEventHandler.cs

@@ -15,6 +15,11 @@ namespace Elsa.Services
         /// </summary>
         Task ActivityExecutedAsync(WorkflowExecutionContext workflowExecutionContext, IActivity activity, CancellationToken cancellationToken);
         
+        /// <summary>
+        /// Invoked when an activity has faulted.
+        /// </summary>
+        Task ActivityFaultedAsync(WorkflowExecutionContext workflowExecutionContext, IActivity activity, string message, CancellationToken cancellationToken);
+        
         /// <summary>
         /// Invoked when halted activities are about to be executed.
         /// </summary>

src/core/Elsa.Abstractions/Services/WorkflowEventHandlerBase.cs

@@ -6,19 +6,36 @@ namespace Elsa.Services
 {
     public abstract class WorkflowEventHandlerBase : IWorkflowEventHandler
     {
-        public virtual Task ActivityExecutedAsync(WorkflowExecutionContext workflowExecutionContext, IActivity activity, CancellationToken cancellationToken)
+        public virtual Task ActivityExecutedAsync(
+            WorkflowExecutionContext workflowExecutionContext,
+            IActivity activity,
+            CancellationToken cancellationToken)
         {
             ActivityExecuted(workflowExecutionContext, activity);
             return Task.CompletedTask;
         }
 
-        public virtual Task InvokingHaltedActivitiesAsync(WorkflowExecutionContext workflowExecutionContext, CancellationToken cancellationToken)
+        public virtual Task ActivityFaultedAsync(
+            WorkflowExecutionContext workflowExecutionContext,
+            IActivity activity,
+            string message,
+            CancellationToken cancellationToken)
+        {
+            ActivityFaulted(workflowExecutionContext, activity, message);
+            return Task.CompletedTask;
+        }
+
+        public virtual Task InvokingHaltedActivitiesAsync(
+            WorkflowExecutionContext workflowExecutionContext,
+            CancellationToken cancellationToken)
         {
             InvokingHaltedActivities(workflowExecutionContext);
             return Task.CompletedTask;
         }
 
-        public virtual Task WorkflowInvokedAsync(WorkflowExecutionContext workflowExecutionContext, CancellationToken cancellationToken)
+        public virtual Task WorkflowInvokedAsync(
+            WorkflowExecutionContext workflowExecutionContext,
+            CancellationToken cancellationToken)
         {
             WorkflowInvoked(workflowExecutionContext);
             return Task.CompletedTask;
@@ -27,11 +44,18 @@ namespace Elsa.Services
         protected virtual void ActivityExecuted(WorkflowExecutionContext workflowExecutionContext, IActivity activity)
         {
         }
-        
+
+        protected virtual void ActivityFaulted(
+            WorkflowExecutionContext workflowExecutionContext,
+            IActivity activity,
+            string message)
+        {
+        }
+
         protected virtual void InvokingHaltedActivities(WorkflowExecutionContext workflowExecutionContext)
         {
         }
-        
+
         protected virtual void WorkflowInvoked(WorkflowExecutionContext workflowExecutionContext)
         {
         }

src/core/Elsa.Core/Activities/ControlFlow/Join.cs

@@ -98,7 +98,7 @@ namespace Elsa.Activities.ControlFlow
             // For each inbound connection, record the transition.
             foreach (var inboundConnection in inboundConnections)
             {
-                var joinActivity = (Join) inboundConnection.Target.Activity;
+                var joinActivity = (Join)inboundConnection.Target.Activity;
                 var inboundTransitions = joinActivity.InboundTransitions ?? new List<string>();
                 joinActivity.InboundTransitions = inboundTransitions
                     .Union(new[] { GetTransitionKey(inboundConnection) })
@@ -115,7 +115,9 @@ namespace Elsa.Activities.ControlFlow
             return $"@{sourceActivityId}_{sourceOutcomeName}";
         }
 
-        Task IWorkflowEventHandler.ActivityExecutedAsync(WorkflowExecutionContext workflowContext, IActivity activity,
+        Task IWorkflowEventHandler.ActivityExecutedAsync(
+            WorkflowExecutionContext workflowContext,
+            IActivity activity,
             CancellationToken cancellationToken)
         {
             RecordInboundTransitions(workflowContext, activity);
@@ -123,10 +125,18 @@ namespace Elsa.Activities.ControlFlow
             return Task.CompletedTask;
         }
 
-        Task IWorkflowEventHandler.InvokingHaltedActivitiesAsync(WorkflowExecutionContext workflowExecutionContext,
+        public Task ActivityFaultedAsync(
+            WorkflowExecutionContext workflowExecutionContext,
+            IActivity activity,
+            string message,
             CancellationToken cancellationToken) => Task.CompletedTask;
 
-        Task IWorkflowEventHandler.WorkflowInvokedAsync(WorkflowExecutionContext workflowExecutionContext,
+        Task IWorkflowEventHandler.InvokingHaltedActivitiesAsync(
+            WorkflowExecutionContext workflowExecutionContext,
+            CancellationToken cancellationToken) => Task.CompletedTask;
+
+        Task IWorkflowEventHandler.WorkflowInvokedAsync(
+            WorkflowExecutionContext workflowExecutionContext,
             CancellationToken cancellationToken) => Task.CompletedTask;
     }
 }

src/core/Elsa.Core/Extensions/ServiceCollectionExtensions.cs

@@ -7,6 +7,7 @@ using Elsa.Activities.Workflows;
 using Elsa.AutoMapper.Extensions;
 using Elsa.Expressions;
 using Elsa.Mapping;
+using Elsa.Persistence;
 using Elsa.Persistence.Memory;
 using Elsa.Runtime;
 using Elsa.Scripting;
@@ -16,6 +17,7 @@ using Elsa.Services;
 using Elsa.Services.Models;
 using Elsa.StartupTasks;
 using Elsa.WorkflowBuilders;
+using Elsa.WorkflowEventHandlers;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using NodaTime;
@@ -61,6 +63,7 @@ namespace Elsa.Extensions
                 .AddScoped<IScopedWorkflowInvoker, ScopedWorkflowInvoker>()
                 .AddScoped<IActivityResolver, ActivityResolver>()
                 .AddScoped<IWorkflowBuilder, WorkflowBuilder>()
+                .AddScoped<IWorkflowEventHandler, ActivityLoggingWorkflowEventHandler>()
                 .AddStartupTask<PopulateRegistryTask>()
                 .AddSingleton<Func<IWorkflowBuilder>>(sp => sp.GetRequiredService<IWorkflowBuilder>)
                 .AddAutoMapperProfile<WorkflowDefinitionProfile>(ServiceLifetime.Singleton)

src/core/Elsa.Core/Results/FaultWorkflowResult.cs

@@ -1,6 +1,11 @@
 using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Elsa.Extensions;
 using Elsa.Services;
 using Elsa.Services.Models;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
 
 namespace Elsa.Results
 {
@@ -11,14 +16,25 @@ namespace Elsa.Results
         public FaultWorkflowResult(Exception exception) : this(exception.Message)
         {
         }
-        
+
         public FaultWorkflowResult(string errorMessage)
         {
             this.errorMessage = errorMessage;
         }
-        
-        protected override void Execute(IWorkflowInvoker invoker, WorkflowExecutionContext workflowContext)
+
+        public override async Task ExecuteAsync(
+            IWorkflowInvoker invoker,
+            WorkflowExecutionContext workflowContext,
+            CancellationToken cancellationToken)
         {
+            var eventHandlers = workflowContext.ServiceProvider.GetServices<IWorkflowEventHandler>();
+            var logger = workflowContext.ServiceProvider.GetRequiredService<ILogger<FaultWorkflowResult>>();
+            var currentActivity = workflowContext.CurrentActivity;
+            
+            await eventHandlers.InvokeAsync(
+                x => x.ActivityFaultedAsync(workflowContext, currentActivity, errorMessage, cancellationToken),
+                logger);
+
             workflowContext.Fault(workflowContext.CurrentActivity, errorMessage);
         }
     }

src/core/Elsa.Core/WorkflowEventHandlers/ActivityLoggingWorkflowEventHandler.cs

@@ -0,0 +1,32 @@
+using Elsa.Models;
+using Elsa.Services;
+using Elsa.Services.Models;
+using NodaTime;
+
+namespace Elsa.WorkflowEventHandlers
+{
+    public class ActivityLoggingWorkflowEventHandler : WorkflowEventHandlerBase
+    {
+        private readonly IClock clock;
+
+        public ActivityLoggingWorkflowEventHandler(IClock clock)
+        {
+            this.clock = clock;
+        }
+
+        protected override void ActivityExecuted(WorkflowExecutionContext workflowExecutionContext, IActivity activity)
+        {
+            workflowExecutionContext.Workflow.ExecutionLog.Add(
+                new LogEntry(activity.Id, clock.GetCurrentInstant(), "Executed"));
+        }
+
+        protected override void ActivityFaulted(
+            WorkflowExecutionContext workflowExecutionContext,
+            IActivity activity,
+            string message)
+        {
+            workflowExecutionContext.Workflow.ExecutionLog.Add(
+                new LogEntry(activity.Id, clock.GetCurrentInstant(), message, true));
+        }
+    }
+}

src/core/Elsa.Core/WorkflowEventHandlers/PersistenceWorkflowEventHandler.cs

@@ -1,35 +1,36 @@
-using System.Threading;
-using System.Threading.Tasks;
-using Elsa.Persistence;
-using Elsa.Services.Models;
-
-namespace Elsa.Services
-{
-    public class PersistenceWorkflowEventHandler : WorkflowEventHandlerBase
-    {
-        private readonly IWorkflowInstanceStore workflowInstanceStore;
-
-        public PersistenceWorkflowEventHandler(IWorkflowInstanceStore workflowInstanceStore)
-        {
-            this.workflowInstanceStore = workflowInstanceStore;
-        }
-
-        public override async Task InvokingHaltedActivitiesAsync(WorkflowExecutionContext workflowExecutionContext,
-            CancellationToken cancellationToken)
-        {
-            await SaveWorkflowAsync(workflowExecutionContext.Workflow, cancellationToken);
-        }
-
-        public override async Task WorkflowInvokedAsync(WorkflowExecutionContext workflowExecutionContext,
-            CancellationToken cancellationToken)
-        {
-            await SaveWorkflowAsync(workflowExecutionContext.Workflow, cancellationToken);
-        }
-
-        private async Task SaveWorkflowAsync(Workflow workflow, CancellationToken cancellationToken)
-        {
-            var workflowInstance = workflow.ToInstance();
-            await workflowInstanceStore.SaveAsync(workflowInstance, cancellationToken);
-        }
-    }
+using System.Threading;
+using System.Threading.Tasks;
+using Elsa.Persistence;
+using Elsa.Services;
+using Elsa.Services.Models;
+
+namespace Elsa.WorkflowEventHandlers
+{
+    public class PersistenceWorkflowEventHandler : WorkflowEventHandlerBase
+    {
+        private readonly IWorkflowInstanceStore workflowInstanceStore;
+
+        public PersistenceWorkflowEventHandler(IWorkflowInstanceStore workflowInstanceStore)
+        {
+            this.workflowInstanceStore = workflowInstanceStore;
+        }
+
+        public override async Task InvokingHaltedActivitiesAsync(WorkflowExecutionContext workflowExecutionContext,
+            CancellationToken cancellationToken)
+        {
+            await SaveWorkflowAsync(workflowExecutionContext.Workflow, cancellationToken);
+        }
+
+        public override async Task WorkflowInvokedAsync(WorkflowExecutionContext workflowExecutionContext,
+            CancellationToken cancellationToken)
+        {
+            await SaveWorkflowAsync(workflowExecutionContext.Workflow, cancellationToken);
+        }
+
+        private async Task SaveWorkflowAsync(Workflow workflow, CancellationToken cancellationToken)
+        {
+            var workflowInstance = workflow.ToInstance();
+            await workflowInstanceStore.SaveAsync(workflowInstance, cancellationToken);
+        }
+    }
 }

src/dashboard/Elsa.Dashboard/Areas/Elsa/Controllers/WorkflowDefinitionController.cs

@@ -27,6 +27,7 @@ namespace Elsa.Dashboard.Areas.Elsa.Controllers
         private readonly IWorkflowInstanceStore workflowInstanceStore;
         private readonly IWorkflowPublisher publisher;
         private readonly IWorkflowSerializer serializer;
+        private readonly IWorkflowFactory workflowFactory;
         private readonly IOptions<ElsaDashboardOptions> options;
         private readonly IIdGenerator idGenerator;
         private readonly INotifier notifier;
@@ -36,6 +37,7 @@ namespace Elsa.Dashboard.Areas.Elsa.Controllers
             IWorkflowInstanceStore workflowInstanceStore,
             IWorkflowPublisher publisher,
             IWorkflowSerializer serializer,
+            IWorkflowFactory workflowFactory,
             IOptions<ElsaDashboardOptions> options,
             IIdGenerator idGenerator,
             INotifier notifier)
@@ -44,6 +46,7 @@ namespace Elsa.Dashboard.Areas.Elsa.Controllers
             this.workflowDefinitionStore = workflowDefinitionStore;
             this.workflowInstanceStore = workflowInstanceStore;
             this.serializer = serializer;
+            this.workflowFactory = workflowFactory;
             this.options = options;
             this.idGenerator = idGenerator;
             this.notifier = notifier;
@@ -72,16 +75,17 @@ namespace Elsa.Dashboard.Areas.Elsa.Controllers
         [HttpGet("create")]
         public ViewResult Create()
         {
-            var workflow = publisher.New();
+            var workflowDefinition = publisher.New();
+            var workflow = workflowFactory.CreateWorkflow(workflowDefinition);
 
             var model = new WorkflowDefinitionEditModel
             {
-                Name = workflow.Name,
-                Json = serializer.Serialize(workflow, JsonTokenFormatter.FormatName),
+                Name = workflowDefinition.Name,
+                Workflow = workflow,
                 ActivityDefinitions = options.Value.ActivityDefinitions.ToArray(),
-                IsSingleton = workflow.IsSingleton,
-                IsDisabled = workflow.IsDisabled,
-                Description = workflow.Description
+                IsSingleton = workflowDefinition.IsSingleton,
+                IsDisabled = workflowDefinition.IsDisabled,
+                Description = workflowDefinition.Description
             };
 
             return View(model);
@@ -103,19 +107,18 @@ namespace Elsa.Dashboard.Areas.Elsa.Controllers
         [HttpGet("edit/{id}")]
         public async Task<IActionResult> Edit(string id, CancellationToken cancellationToken)
         {
-            var workflow = await publisher.GetDraftAsync(id, cancellationToken);
+            var workflowDefinition = await publisher.GetDraftAsync(id, cancellationToken);
 
-            if (workflow == null)
+            if (workflowDefinition == null)
                 return NotFound();
 
             var model = new WorkflowDefinitionEditModel
             {
-                Id = workflow.DefinitionId,
-                Name = workflow.Name,
-                Description = workflow.Description,
-                IsSingleton = workflow.IsSingleton,
-                IsDisabled = workflow.IsDisabled,
-                Json = serializer.Serialize(workflow, JsonTokenFormatter.FormatName),
+                Id = workflowDefinition.DefinitionId,
+                Name = workflowDefinition.Name,
+                Description = workflowDefinition.Description,
+                IsSingleton = workflowDefinition.IsSingleton,
+                IsDisabled = workflowDefinition.IsDisabled,
                 ActivityDefinitions = options.Value.ActivityDefinitions.ToArray()
             };
 

src/dashboard/Elsa.Dashboard/Areas/Elsa/Controllers/WorkflowInstanceController.cs

@@ -11,6 +11,7 @@ using Elsa.Models;
 using Elsa.Persistence;
 using Elsa.Serialization;
 using Elsa.Serialization.Formatters;
+using Elsa.Services;
 using Jint.Native.Json;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Extensions.Options;
@@ -25,6 +26,7 @@ namespace Elsa.Dashboard.Areas.Elsa.Controllers
         private readonly IWorkflowDefinitionStore workflowDefinitionStore;
         private readonly IOptions<ElsaDashboardOptions> options;
         private readonly IWorkflowSerializer serializer;
+        private readonly IWorkflowFactory workflowFactory;
         private readonly INotifier notifier;
 
         public WorkflowInstanceController(
@@ -32,12 +34,14 @@ namespace Elsa.Dashboard.Areas.Elsa.Controllers
             IWorkflowDefinitionStore workflowDefinitionStore,
             IOptions<ElsaDashboardOptions> options,
             IWorkflowSerializer serializer,
+            IWorkflowFactory workflowFactory,
             INotifier notifier)
         {
             this.workflowInstanceStore = workflowInstanceStore;
             this.workflowDefinitionStore = workflowDefinitionStore;
             this.options = options;
             this.serializer = serializer;
+            this.workflowFactory = workflowFactory;
             this.notifier = notifier;
         }
 
@@ -90,14 +94,13 @@ namespace Elsa.Dashboard.Areas.Elsa.Controllers
                 cancellationToken
             );
 
-            var json = serializer.Serialize(definition, JsonTokenFormatter.FormatName);
+            var workflow = workflowFactory.CreateWorkflow(definition, Variables.Empty, instance);
 
             var model = new WorkflowInstanceDetailsModel
             {
                 ReturnUrl = returnUrl,
-                Json = json,
                 WorkflowDefinition = definition,
-                WorkflowInstance = instance,
+                Workflow = workflow,
                 ActivityDefinitions = options.Value.ActivityDefinitions.ToArray()
             };
 

src/dashboard/Elsa.Dashboard/Areas/Elsa/ViewModels/WorkflowDefinitionEditModel.cs

@@ -1,3 +1,4 @@
+using Elsa.Services.Models;
 using Elsa.WorkflowDesigner.Models;
 
 namespace Elsa.Dashboard.Areas.Elsa.ViewModels
@@ -5,6 +6,7 @@ namespace Elsa.Dashboard.Areas.Elsa.ViewModels
     public class WorkflowDefinitionEditModel
     {
         public string Id { get; set; }
+        public Workflow Workflow { get; set; }
         public string Json { get; set; }
         public string SubmitAction { get; set; }
         public string Name { get; set; }

src/dashboard/Elsa.Dashboard/Areas/Elsa/ViewModels/WorkflowInstanceDetailsModel.cs

@@ -1,4 +1,5 @@
 using Elsa.Models;
+using Elsa.Services.Models;
 using ActivityDefinition = Elsa.WorkflowDesigner.Models.ActivityDefinition;
 
 namespace Elsa.Dashboard.Areas.Elsa.ViewModels
@@ -6,9 +7,8 @@ namespace Elsa.Dashboard.Areas.Elsa.ViewModels
     public class WorkflowInstanceDetailsModel
     {
         public string ReturnUrl { get; set; }
-        public string Json { get; set; }
         public WorkflowDefinitionVersion WorkflowDefinition { get; set; }
-        public WorkflowInstance WorkflowInstance { get; set; }
+        public Workflow Workflow { get; set; }
         public ActivityDefinition[] ActivityDefinitions { get; set; }
     }
 }

src/dashboard/Elsa.Dashboard/Areas/Elsa/Views/Shared/WorkflowDefinitionEditor.cshtml

@@ -24,8 +24,7 @@
                 </div>
                 <div class="card-body">
                     <form asp-action="@formAction">
-                        <input asp-for="Json" id="workflowData" type="hidden"/>
-                        <vc:workflow-designer id="designerHost" activity-definitions="@Model.ActivityDefinitions"/>
+                        <vc:workflow-designer id="designerHost" data-activity-definitions="@Model.ActivityDefinitions" data-workflow="@Model.Workflow"/>
                         <div class="text-center">
                             <button asp-for="SubmitAction" name="SubmitAction" type="submit" value="draft" class="btn btn-primary mt-4">Save Draft</button>
                             <button asp-for="SubmitAction" name="SubmitAction" type="submit" value="publish" class="btn btn-success mt-4">Publish</button>

src/dashboard/Elsa.Dashboard/Areas/Elsa/Views/Shared/_Layout.cshtml

@@ -32,7 +32,7 @@
     <!-- CSS Files -->
     <link href="~/assets/css/argon-dashboard.css?v=1.1.0" rel="stylesheet"/>
     <link href="~/assets/css/elsa.css?v=1.1.0" rel="stylesheet"/>
-    <script src='https://unpkg.com/@@elsa-workflows/elsa-workflow-designer@0.0.49/dist/elsa-workflow-designer.js'></script>
+    <script src='https://unpkg.com/@@elsa-workflows/elsa-workflow-designer@0.0.51/dist/elsa-workflow-designer.js'></script>
     @await RenderSectionAsync("HeadScripts", false)
 </head>
 

src/dashboard/Elsa.Dashboard/Areas/Elsa/Views/WorkflowInstance/Details.cshtml

@@ -1,5 +1,5 @@
 @model WorkflowInstanceDetailsModel
-<div class="container-fluid mt--7" data-workflow="@Model.Json">
+<div class="container-fluid mt-7">
     <div class="row">
         <div class="col">
             <div class="card bg-secondary shadow">
@@ -18,7 +18,7 @@
                     </div>
                 </div>
                 <div class="card-body">
-                    <vc:workflow-designer id="designerHost" activity-definitions="@Model.ActivityDefinitions" />
+                    <vc:workflow-designer id="designerHost" activity-definitions="@Model.ActivityDefinitions" workflow="@Model.Workflow"/>
                     <div class="text-center">
                         <a href="@Model.ReturnUrl" class="btn btn-primary mt-4">Back</a>
                     </div>

src/dashboard/Elsa.Dashboard/Theme/argon-dashboard/assets/js/workflow-instance-viewer.js

@@ -1,7 +1,4 @@
 const designer = document.querySelector("#designerHost");
-let workflow = null;
-
-//designer.addEventListener('componentReady', onWorkflowDesignerReady);
 
 function exportWorkflow() {
     designer.export({
@@ -10,17 +7,4 @@ function exportWorkflow() {
         mimeType: 'application/json',
         displayName: 'JSON'
     });
-}
-
-function onWorkflowDesignerReady() {
-    const input = document.querySelector('[data-workflow]');
-    const json = input.attributes['data-workflow'].value;
-
-    if (!json)
-        return;
-
-    designer.workflow = workflow = JSON.parse(json);
-}
-
-// Temporary workaround until I figure out how to listen for the workflow designer component's ready event.
-setTimeout(onWorkflowDesignerReady, 100);
+}

src/dashboard/Elsa.WorkflowDesigner/ActivityDescriber.cs

@@ -63,13 +63,13 @@ namespace Elsa.WorkflowDesigner
                     yield break;
 
                 yield return new ActivityPropertyDescriptor
-                {
-                    Name = (activityProperty.Name ?? propertyInfo.Name).Camelize(),
-                    Label = activityProperty.Label ?? propertyInfo.Name.Humanize(LetterCasing.Title),
-                    Type = (activityProperty.Type ?? DeterminePropertyType(propertyInfo)).Camelize(),
-                    Hint = activityProperty.Hint,
-                    Options = GetPropertyTypeOptions(propertyInfo)
-                };
+                (
+                    (activityProperty.Name ?? propertyInfo.Name).Camelize(),
+                    (activityProperty.Type ?? DeterminePropertyType(propertyInfo)).Camelize(),
+                    activityProperty.Label ?? propertyInfo.Name.Humanize(LetterCasing.Title),
+                    activityProperty.Hint,
+                    GetPropertyTypeOptions(propertyInfo)
+                );
             }
         }
         

src/dashboard/Elsa.WorkflowDesigner/Elsa.WorkflowDesigner.csproj

@@ -2,7 +2,8 @@
 
     <PropertyGroup>
         <TargetFramework>netstandard2.0</TargetFramework>
-        <LangVersion>latest</LangVersion>
+        <LangVersion>8.0</LangVersion>
+        <Nullable>enable</Nullable>
         <PackageVersion>1.0.0</PackageVersion>
         <Authors>Sipke Schoorstra</Authors>
         <Description>Elsa is a set of workflowing libraries and tools to enable super-fast workflowing capabilities in any .NET Core application.</Description>

src/dashboard/Elsa.WorkflowDesigner/Models/ActivityDefinition.cs

@@ -4,14 +4,19 @@ namespace Elsa.WorkflowDesigner.Models
     {
         public ActivityDefinition()
         {
+            Type = "Activity";
             Properties = new ActivityPropertyDescriptor[0];
+            Category = "Miscellaneous";
+            DisplayName = "Activity";
+            Properties = new ActivityPropertyDescriptor[0];
+            Designer = new ActivityDesignerSettings();
         }
 
         public string Type { get; set; }
         public string DisplayName { get; set; }
-        public string Description { get; set; }
+        public string? Description { get; set; }
         public string Category { get; set; }
-        public string Icon { get; set; }
+        public string? Icon { get; set; }
         public ActivityPropertyDescriptor[] Properties { get; set; }
         public ActivityDesignerSettings Designer { get; set; }
     }

src/dashboard/Elsa.WorkflowDesigner/Models/ActivityDesignerSettings.cs

@@ -2,7 +2,7 @@ namespace Elsa.WorkflowDesigner.Models
 {
     public class ActivityDesignerSettings
     {
-        public object Description { get; set; }
-        public object Outcomes { get; set; }
+        public object? Description { get; set; }
+        public object? Outcomes { get; set; }
     }
 }

src/dashboard/Elsa.WorkflowDesigner/Models/ActivityPropertyDescriptor.cs

@@ -2,10 +2,19 @@ namespace Elsa.WorkflowDesigner.Models
 {
     public class ActivityPropertyDescriptor
     {
-        public string Name { get; set; }
-        public string Type { get; set; }
-        public string Label { get; set; }
-        public string Hint { get; set; }
-        public object Options { get; set; }
+        public ActivityPropertyDescriptor(string name, string type, string label, string? hint = null, object? options = null)
+        {
+            Name = name;
+            Type = type;
+            Label = label;
+            Hint = hint;
+            Options = options;
+        }
+        
+        public string Name { get; }
+        public string Type { get; }
+        public string Label { get; }
+        public string? Hint { get; }
+        public object? Options { get; }
     }
 }

src/dashboard/Elsa.WorkflowDesigner/ViewComponents/WorkflowDesignerViewComponent.cs

@@ -1,33 +1,47 @@
-using Elsa.WorkflowDesigner.Models;
+using Elsa.Serialization;
+using Elsa.Services.Models;
 using Elsa.WorkflowDesigner.ViewModels;
 using Microsoft.AspNetCore.Mvc;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Serialization;
+using ActivityDefinition = Elsa.WorkflowDesigner.Models.ActivityDefinition;
 
 namespace Elsa.WorkflowDesigner.ViewComponents
 {
     public class WorkflowDesignerViewComponent : ViewComponent
     {
-        public IViewComponentResult Invoke(ActivityDefinition[] activityDefinitions, string id)
+        private readonly IWorkflowSerializer serializer;
+
+        public WorkflowDesignerViewComponent(IWorkflowSerializer serializer)
         {
-            var model = new WorkflowDesignerViewComponentModel
-            {
-                Id = id,
-                ActivityDefinitionsJson = GetActivityDefinitionOptions(activityDefinitions)
-            };
+            this.serializer = serializer;
+        }
+
+        public IViewComponentResult Invoke(
+            string id,
+            ActivityDefinition[]? activityDefinitions = null,
+            Workflow? workflow = null)
+        {
+            var model = new WorkflowDesignerViewComponentModel(
+                id,
+                Serialize(activityDefinitions ?? new ActivityDefinition[0]),
+                Serialize(workflow)
+            );
 
             return View(model);
         }
 
-        private string GetActivityDefinitionOptions(ActivityDefinition[] activityDefinitions)
+        private static string? Serialize(object? value)
         {
-            var definitions = activityDefinitions ?? new ActivityDefinition[0];
+            if (value == null)
+                return null;
+
             var settings = new JsonSerializerSettings
             {
                 ContractResolver = new CamelCasePropertyNamesContractResolver(),
                 NullValueHandling = NullValueHandling.Ignore
             };
-            return JsonConvert.SerializeObject(definitions, settings);
+            return JsonConvert.SerializeObject(value, settings);
         }
     }
 }

src/dashboard/Elsa.WorkflowDesigner/ViewModels/WorkflowDesignerViewComponentModel.cs

@@ -2,7 +2,15 @@ namespace Elsa.WorkflowDesigner.ViewModels
 {
     public class WorkflowDesignerViewComponentModel
     {
-        public string Id { get; set; }
-        public string ActivityDefinitionsJson { get; set; }
+        public WorkflowDesignerViewComponentModel(string id, string? activityDefinitionsJson, string? workflowJson)
+        {
+            Id = id;
+            ActivityDefinitionsJson = activityDefinitionsJson;
+            WorkflowJson = workflowJson;
+        }
+
+        public string Id { get; }
+        public string? ActivityDefinitionsJson { get; set; }
+        public string? WorkflowJson { get; set; }
     }
 }