Initial revision

.vscode/launch.json

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+{
+   // Use IntelliSense to find out which attributes exist for C# debugging
+   // Use hover for the description of the existing attributes
+   // For further information visit https://github.com/OmniSharp/omnisharp-vscode/blob/master/debugger-launchjson.md
+   "version": "0.2.0",
+   "configurations": [
+        {
+            "name": ".NET Core Launch (web)",
+            "type": "coreclr",
+            "request": "launch",
+            "preLaunchTask": "build",
+            // If you have changed target frameworks, make sure to update the program path.
+            "program": "${workspaceFolder}/viewer/bin/Debug/netcoreapp2.1/viewer.dll",
+            "args": [],
+            "cwd": "${workspaceFolder}/viewer",
+            "stopAtEntry": false,
+            "internalConsoleOptions": "openOnSessionStart",
+            "launchBrowser": {
+                "enabled": true,
+                "args": "${auto-detect-url}",
+                "windows": {
+                    "command": "cmd.exe",
+                    "args": "/C start ${auto-detect-url}"
+                },
+                "osx": {
+                    "command": "open"
+                },
+                "linux": {
+                    "command": "xdg-open"
+                }
+            },
+            "env": {
+                "ASPNETCORE_ENVIRONMENT": "Development"
+            },
+            "sourceFileMap": {
+                "/Views": "${workspaceFolder}/Views"
+            }
+        },
+        {
+            "name": ".NET Core Attach",
+            "type": "coreclr",
+            "request": "attach",
+            "processId": "${command:pickProcess}"
+        }
+    ]
+}

AzureEventGridViewer.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 15
+VisualStudioVersion = 15.0.27703.2000
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "viewer", "viewer\viewer.csproj", "{B76DCFAF-1283-4BE7-86E6-28FF41C300F0}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{B76DCFAF-1283-4BE7-86E6-28FF41C300F0}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B76DCFAF-1283-4BE7-86E6-28FF41C300F0}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B76DCFAF-1283-4BE7-86E6-28FF41C300F0}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B76DCFAF-1283-4BE7-86E6-28FF41C300F0}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {A9E98DBE-C8B1-4612-A197-DD257FEF3709}
+	EndGlobalSection
+EndGlobal

viewer/.vscode/launch.json

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+{
+   // Use IntelliSense to find out which attributes exist for C# debugging
+   // Use hover for the description of the existing attributes
+   // For further information visit https://github.com/OmniSharp/omnisharp-vscode/blob/master/debugger-launchjson.md
+   "version": "0.2.0",
+   "configurations": [
+        {
+            "name": ".NET Core Launch (web)",
+            "type": "coreclr",
+            "request": "launch",
+            "preLaunchTask": "build",
+            // If you have changed target frameworks, make sure to update the program path.
+            "program": "${workspaceFolder}/bin/Debug/netcoreapp2.1/viewer.dll",
+            "args": [],
+            "cwd": "${workspaceFolder}",
+            "stopAtEntry": false,
+            "internalConsoleOptions": "openOnSessionStart",
+            "launchBrowser": {
+                "enabled": true,
+                "args": "${auto-detect-url}",
+                "windows": {
+                    "command": "cmd.exe",
+                    "args": "/C start ${auto-detect-url}"
+                },
+                "osx": {
+                    "command": "open"
+                },
+                "linux": {
+                    "command": "xdg-open"
+                }
+            },
+            "env": {
+                "ASPNETCORE_ENVIRONMENT": "Development"
+            },
+            "sourceFileMap": {
+                "/Views": "${workspaceFolder}/Views"
+            }
+        },
+        {
+            "name": ".NET Core Attach",
+            "type": "coreclr",
+            "request": "attach",
+            "processId": "${command:pickProcess}"
+        }
+    ]
+}

viewer/.vscode/tasks.json

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+{
+    "version": "2.0.0",
+    "tasks": [
+        {
+            "label": "build",
+            "command": "dotnet",
+            "type": "process",
+            "args": [
+                "build",
+                "${workspaceFolder}/viewer.csproj"
+            ],
+            "problemMatcher": "$msCompile"
+        }
+    ]
+}

viewer/Controllers/HomeController.cs

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+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc;
+using viewer.Models;
+
+namespace viewer.Controllers
+{
+    public class HomeController : Controller
+    {
+        public IActionResult Index()
+        {
+            return View();
+        }
+
+        public IActionResult About()
+        {
+            ViewData["Message"] = "Your application description page.";
+
+            return View();
+        }
+
+        public IActionResult Contact()
+        {
+            ViewData["Message"] = "Your contact page.";
+
+            return View();
+        }
+
+        public IActionResult Privacy()
+        {
+            return View();
+        }
+
+        [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
+        public IActionResult Error()
+        {
+            return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
+        }
+    }
+}

viewer/Controllers/UpdatesController.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.IO;
+using System.Threading.Tasks;
+using System.Net;
+using System.Text;
+using System.Net.Http;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+using Microsoft.AspNetCore.SignalR;
+using Microsoft.AspNetCore.Mvc;
+using viewer.Hubs;
+using viewer.Models;
+
+namespace viewer.Controllers
+{
+    [Route("api/[controller]")]
+    public class UpdatesController : Controller
+    {
+        #region Data Members
+
+        private bool EventTypeSubcriptionValidation
+            => HttpContext.Request.Headers["aeg-event-type"].FirstOrDefault() ==
+               "SubscriptionValidation";
+
+        private bool EventTypeNotification
+            => HttpContext.Request.Headers["aeg-event-type"].FirstOrDefault() ==
+               "Notification";
+
+        private readonly IHubContext<GridEventsHub> _hubContext;
+
+        #endregion
+
+        #region Constructors
+
+        public UpdatesController(IHubContext<GridEventsHub> gridEventsHubContext)
+        {
+            this._hubContext = gridEventsHubContext;
+        }
+
+        #endregion
+
+        #region Public Methods
+
+        [HttpPost]
+        public async Task<IActionResult> Post()
+        {
+            using (var reader = new StreamReader(Request.Body, Encoding.UTF8))
+            {
+                var jsonContent = await reader.ReadToEndAsync();
+
+                // Check the event type.
+                // Return the validation code if it's 
+                // a subscription validation request. 
+                if (EventTypeSubcriptionValidation)
+                {
+                    return await HandleValidation(jsonContent);
+                }
+                else if (EventTypeNotification)
+                {
+                    // Check to see if this is passed in using
+                    // the CloudEvents schema
+                    if (IsCloudEvent(jsonContent))
+                    {
+                        return await HandleCloudEvent(jsonContent);
+                    }
+
+                    return await HandleGridEvents(jsonContent);
+                }
+
+                return BadRequest();                
+            }
+        }
+
+        #endregion
+
+        #region Private Methods
+
+        private async Task<JsonResult> HandleValidation(string jsonContent)
+        {
+            var gridEvent =
+                JsonConvert.DeserializeObject<List<GridEvent<Dictionary<string, string>>>>(jsonContent)
+                    .First();
+
+            await this._hubContext.Clients.All.SendAsync(
+                "gridupdate",
+                gridEvent.Id,
+                gridEvent.EventType,
+                gridEvent.Subject,
+                gridEvent.EventTime.ToLongTimeString(),
+                jsonContent.ToString());
+
+            // Retrieve the validation code and echo back.
+            var validationCode = gridEvent.Data["validationCode"];
+            return new JsonResult(new
+            {
+                validationResponse = validationCode
+            });
+        }
+
+        private async Task<IActionResult> HandleGridEvents(string jsonContent)
+        {
+            var events = JArray.Parse(jsonContent);
+            foreach (var e in events)
+            {
+                // Invoke a method on the clients for 
+                // an event grid notiification.                        
+                var details = JsonConvert.DeserializeObject<GridEvent<dynamic>>(e.ToString());
+                await this._hubContext.Clients.All.SendAsync(
+                    "gridupdate",
+                    details.Id,
+                    details.EventType,
+                    details.Subject,
+                    details.EventTime.ToLongTimeString(),
+                    e.ToString());
+            }
+
+            return Ok();
+        }
+
+        private async Task<IActionResult> HandleCloudEvent(string jsonContent)
+        {
+            var details = JsonConvert.DeserializeObject<CloudEvent<dynamic>>(jsonContent);
+
+            // CloudEvents schema and mapping to 
+            // Event Grid: https://docs.microsoft.com/en-us/azure/event-grid/cloudevents-schema 
+            await this._hubContext.Clients.All.SendAsync(
+                "gridupdate",
+                details.EventId,
+                details.EventType,
+                details.Source,
+                details.EventTime,
+                jsonContent
+            );
+
+            return Ok();
+        }
+
+        private static bool IsCloudEvent(string jsonContent)
+        {
+            // Cloud events are sent one at a time, while Grid events
+            // are sent in an array. As a result, the JObject.Parse will 
+            // fail for Grid events. 
+            try
+            {
+                // Attempt to read one JSON object. 
+                var eventData = JObject.Parse(jsonContent);
+
+                // Check for the cloud events version property.
+                var version = eventData["cloudEventsVersion"].Value<string>();
+                if (!string.IsNullOrEmpty(version)) return true;
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine(e);
+            }
+
+            return false;
+        }
+
+        #endregion
+    }
+}

viewer/Hubs/GridEventsHub.cs

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+using Microsoft.AspNetCore.SignalR;
+
+namespace viewer.Hubs
+{
+    public class GridEventsHub: Hub
+    {
+        public GridEventsHub()
+        {            
+        }
+    }
+}

viewer/Models/CloudEvent.cs

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+
+using Newtonsoft.Json;
+
+namespace viewer.Models
+{
+    public class CloudEvent<T> where T : class
+    {
+        [JsonProperty("eventID")]
+        public string EventId { get; set; }
+
+        [JsonProperty("cloudEventsVersion")]
+        public string CloudEventVersion { get; set; }
+
+        [JsonProperty("eventType")]
+        public string EventType { get; set; }
+
+        [JsonProperty("eventTypeVersion")]
+        public string EventTypeVersion { get; set; }
+
+        [JsonProperty("source")]
+        public string Source { get; set; }
+
+        [JsonProperty("eventTime")]
+        public string EventTime { get; set; }
+
+        [JsonProperty("data")]
+        public T Data { get; set; }
+    }
+}