Adding a Functions Filter sample to SampleHost

sample/SampleHost/Filters/ErrorHandler.cs

@@ -0,0 +1,24 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Azure.WebJobs.Host;
+using Microsoft.Extensions.Logging;
+
+namespace SampleHost.Filters
+{
+    /// <summary>
+    /// Sample exception filter that shows how declarative error handling logic
+    /// can be integrated into the execution pipeline.
+    /// </summary>
+    public class ErrorHandlerAttribute : FunctionExceptionFilterAttribute
+    {
+        public override Task OnExceptionAsync(FunctionExceptionContext exceptionContext, CancellationToken cancellationToken)
+        {
+            // custom error handling logic could be written here
+            // (e.g. write a queue message, send a notification, etc.)
+
+            exceptionContext.Logger.LogError($"ErrorHandler called. Function '{exceptionContext.FunctionName}:{exceptionContext.FunctionInstanceId} failed.");
+
+            return Task.CompletedTask;
+        }
+    }
+}

sample/SampleHost/Filters/WorkItemValidator.cs

@@ -0,0 +1,50 @@
+using System.ComponentModel.DataAnnotations;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Azure.WebJobs.Host;
+using Microsoft.Extensions.Logging;
+using SampleHost.Models;
+
+namespace SampleHost.Filters
+{
+    /// <summary>
+    /// Sample invocation filter that demonstrates how declarative validation logic
+    /// can be integrated into the execution pipeline.
+    /// </summary>
+    public class WorkItemValidatorAttribute : FunctionInvocationFilterAttribute
+    {
+        public override Task OnExecutingAsync(FunctionExecutingContext executingContext, CancellationToken cancellationToken)
+        {
+            executingContext.Logger.LogInformation("WorkItemValidator executing...");
+
+            var workItem = executingContext.Arguments.First().Value as WorkItem;
+            string errorMessage = null;
+            if (!TryValidateWorkItem(workItem, out errorMessage))
+            {
+                executingContext.Logger.LogError(errorMessage);
+                throw new ValidationException(errorMessage);
+            }
+                
+            return base.OnExecutingAsync(executingContext, cancellationToken);
+        }
+
+        private static bool TryValidateWorkItem(WorkItem workItem, out string errorMessage)
+        {
+            errorMessage = null;
+
+            if (string.IsNullOrEmpty(workItem.ID))
+            {
+                errorMessage = "ID cannot be null or empty.";
+                return false;
+            }
+            if (workItem.Priority > 100 || workItem.Priority < 0)
+            {
+                errorMessage = "Priority must be between 0 and 100";
+                return false;
+            }
+
+            return true;
+        }
+    }
+}

sample/SampleHost/Functions.cs

@@ -4,9 +4,12 @@
 using System;
 using Microsoft.Azure.WebJobs;
 using Newtonsoft.Json.Linq;
+using SampleHost.Filters;
+using SampleHost.Models;
 
 namespace SampleHost
 {
+    [ErrorHandler]
     public static class Functions
     {
         public static void BlobTrigger(
@@ -24,10 +27,11 @@ namespace SampleHost
             Console.WriteLine($"Poison blob: {container}/{blobName}");
         }
 
-        public static void QueueTrigger(
-            [QueueTrigger("test")] string message)
+        [WorkItemValidator]
+        public static void ProcessWorkItem(
+            [QueueTrigger("test")] WorkItem workItem)
         {
-            Console.WriteLine("Processed message: " + message);
+            Console.WriteLine($"Processed work item {workItem.ID}");
         }
     }
 }

sample/SampleHost/Models/WorkItem.cs

@@ -0,0 +1,11 @@
+namespace SampleHost.Models
+{
+    public class WorkItem
+    {
+        public string ID { get; set; }
+        public int Priority { get; set; }
+        public string Region { get; set; }
+        public int Category { get; set; }
+        public string Description { get; set; }
+    }
+}

sample/SampleHost/Program.cs

@@ -15,6 +15,7 @@ namespace SampleHost
             var config = new JobHostConfiguration();
             config.Queues.VisibilityTimeout = TimeSpan.FromSeconds(15);
             config.Queues.MaxDequeueCount = 3;
+            config.LoggerFactory = new LoggerFactory().AddConsole();
 
             if (config.IsDevelopment)
             {

sample/SampleHost/appsettings.json

@@ -1,6 +1,4 @@
 {
     "ConnectionStrings": {
-        "AzureWebJobsDashboard": "Your connection string here",
-        "AzureWebJobsStorage": "Your connection string here"
     }
 }

src/Microsoft.Azure.WebJobs.Host/Filters/FunctionFilterContext.cs

@@ -26,11 +26,6 @@ namespace Microsoft.Azure.WebJobs.Host
                 throw new ArgumentNullException(nameof(functionName));
             }
 
-            if (logger == null)
-            {
-                throw new ArgumentNullException(nameof(logger));
-            }
-
             if (properties == null)
             {
                 throw new ArgumentNullException(nameof(properties));