Add shared (collaborative) samples

PlatformSamples/AspNetCoreMvc/Controllers/SamplesController.cs

@@ -8,6 +8,8 @@ using Microsoft.AspNetCore.Mvc;
 using AspNetCoreMvc.Models;
 using Ooui;
 using Ooui.AspNetCore;
+using Samples;
+using System.Collections.Concurrent;
 
 namespace AspNetCoreMvc.Controllers
 {
@@ -43,10 +45,13 @@ namespace AspNetCoreMvc.Controllers
                 return samples.ToList ();
             }), true);
 
+        static readonly ConcurrentDictionary<string, Element> sharedSamples =
+            new ConcurrentDictionary<string, Element> ();
+
         public static List<Samples.ISample> Samples => lazySamples.Value;
 
         [Route("/Samples/Run/{name}")]
-        public IActionResult Run (string name)
+        public IActionResult Run (string name, bool shared)
         {
             if (string.IsNullOrWhiteSpace (name) || name.Length > 32)
                 return BadRequest ();
@@ -55,7 +60,18 @@ namespace AspNetCoreMvc.Controllers
             if (s == null)
                 return NotFound ();
 
-            return new ElementResult (s.CreateElement (), title: s.Title + " - Ooui Samples");
+            var element = shared ? GetSharedSample (s) : s.CreateElement ();
+
+            return new ElementResult (element, title: s.Title + " - Ooui Samples");
+        }
+
+        private Element GetSharedSample (ISample s)
+        {
+            if (sharedSamples.TryGetValue (s.Title, out var e))
+                return e;
+            e = s.CreateElement ();
+            sharedSamples[s.Title] = e;
+            return e;
         }
     }
 }

PlatformSamples/AspNetCoreMvc/Views/Home/Index.cshtml

@@ -17,7 +17,10 @@
         <h3>Samples</h3>
         <ul>
 			@foreach (var s in SamplesController.Samples) {
-                <li><a asp-area="" asp-controller="Samples" asp-action="Run" asp-route-name="@s.Title">@s.Title</a></li>
+                <li>
+				    <a asp-area="" asp-controller="Samples" asp-action="Run" asp-route-name="@s.Title">@s.Title</a>
+			        (<a asp-area="" asp-controller="Samples" asp-action="Run" asp-route-name="@s.Title" asp-route-shared="@true">Shared</a>)
+			    </li>
 			}
         </ul>
     </div>

Samples/DrawSample.cs

@@ -17,7 +17,7 @@ namespace Samples
         public Element CreateElement ()
         {
             var heading = new Heading ("Draw");
-            var subtitle = new Paragraph ("Click to draw a collaborative masterpiece");
+            var subtitle = new Paragraph ("Click to draw a masterpiece");
             var canvas = new Canvas {
                 Width = 320,
                 Height = 240,