Avoid null reference exception (#15420)

src/OrchardCore.Modules/OrchardCore.Workflows/Recipes/WorkflowTypeStep.cs

@@ -21,19 +21,21 @@ public class WorkflowTypeStep : IRecipeStepHandler
     {
         private readonly IWorkflowTypeStore _workflowTypeStore;
         private readonly ISecurityTokenService _securityTokenService;
+        private readonly IActionContextAccessor _actionContextAccessor;
+        private readonly IUrlHelperFactory _urlHelperFactory;
         private readonly JsonSerializerOptions _jsonSerializerOptions;
-        private readonly IUrlHelper _urlHelper;
 
         public WorkflowTypeStep(IWorkflowTypeStore workflowTypeStore,
             ISecurityTokenService securityTokenService,
             IActionContextAccessor actionContextAccessor,
-            IOptions<JsonSerializerOptions> jsonSerializerOptions,
-            IUrlHelperFactory urlHelperFactory)
+            IUrlHelperFactory urlHelperFactory,
+            IOptions<JsonSerializerOptions> jsonSerializerOptions)
         {
             _workflowTypeStore = workflowTypeStore;
             _securityTokenService = securityTokenService;
+            _actionContextAccessor = actionContextAccessor;
+            _urlHelperFactory = urlHelperFactory;
             _jsonSerializerOptions = jsonSerializerOptions.Value;
-            _urlHelper = urlHelperFactory.GetUrlHelper(actionContextAccessor.ActionContext);
         }
 
         public async Task ExecuteAsync(RecipeExecutionContext context)
@@ -44,25 +46,30 @@ public async Task ExecuteAsync(RecipeExecutionContext context)
             }
 
             var model = context.Step.ToObject<WorkflowStepModel>();
+            var urlHelper = GetUrlHelper();
 
             foreach (var token in model.Data.Cast<JsonObject>())
             {
                 var workflow = token.ToObject<WorkflowType>(_jsonSerializerOptions);
 
-                foreach (var activity in workflow.Activities.Where(a => a.Name == nameof(HttpRequestEvent)))
-                {
-                    var tokenLifeSpan = activity.Properties["TokenLifeSpan"];
-                    if (tokenLifeSpan != null)
-                    {
-                        activity.Properties["Url"] = ReGenerateHttpRequestEventUrl(workflow, activity, tokenLifeSpan.ToObject<int>());
-                    }
-                }
-
                 var existing = await _workflowTypeStore.GetAsync(workflow.WorkflowTypeId);
 
-                if (existing == null)
+                if (existing is null)
                 {
                     workflow.Id = 0;
+
+                    if (urlHelper is not null)
+                    {
+                        foreach (var activity in workflow.Activities.Where(a => a.Name == nameof(HttpRequestEvent)))
+                        {
+                            if (!activity.Properties.TryGetPropertyValue("TokenLifeSpan", out var tokenLifeSpan))
+                            {
+                                continue;
+                            }
+
+                            activity.Properties["Url"] = ReGenerateHttpRequestEventUrl(urlHelper, workflow, activity, tokenLifeSpan.ToObject<int>());
+                        }
+                    }
                 }
                 else
                 {
@@ -73,12 +80,25 @@ public async Task ExecuteAsync(RecipeExecutionContext context)
             }
         }
 
-        private string ReGenerateHttpRequestEventUrl(WorkflowType workflow, ActivityRecord activity, int tokenLifeSpan)
+        private IUrlHelper _urlHelper;
+
+        private IUrlHelper GetUrlHelper()
+        {
+            // When 'UrlHelper' is instantiated outside a controller's action (e.g., in a BackgroundTask), the ActionContext is null.
+            if (_urlHelper is null && _actionContextAccessor.ActionContext is not null)
+            {
+                _urlHelper = _urlHelperFactory.GetUrlHelper(_actionContextAccessor.ActionContext);
+            }
+
+            return _urlHelper;
+        }
+
+        private string ReGenerateHttpRequestEventUrl(IUrlHelper urlHelper, WorkflowType workflow, ActivityRecord activity, int tokenLifeSpan)
         {
             var token = _securityTokenService.CreateToken(new WorkflowPayload(workflow.WorkflowTypeId, activity.ActivityId),
                 TimeSpan.FromDays(tokenLifeSpan == 0 ? HttpWorkflowController.NoExpiryTokenLifespan : tokenLifeSpan));
 
-            return _urlHelper.Action("Invoke", "HttpWorkflow", new { token });
+            return urlHelper.Action("Invoke", "HttpWorkflow", new { token });
         }
     }