feat(cancellation): exposes cancellation request (example in prime calculator)

GrasshopperAsyncComponent/GH_AsyncComponent.cs

@@ -88,7 +88,7 @@ namespace GrasshopperAsyncComponent
 
     public virtual void DisplayProgress(object sender, System.Timers.ElapsedEventArgs e)
     {
-      if (Workers.Count == 0)
+      if (Workers.Count == 0 || ProgressReports.Values.Count == 0)
       {
         return;
       }
@@ -226,5 +226,24 @@ namespace GrasshopperAsyncComponent
       Message = "Done";
       OnDisplayExpired(true);
     }
+
+    public void RequestCancellation()
+    {
+      foreach (var source in CancellationSources)
+      {
+        source.Cancel();
+      }
+
+      CancellationSources.Clear();
+      Workers.Clear();
+      ProgressReports.Clear();
+      Tasks.Clear();
+
+      Interlocked.Exchange(ref State, 0);
+      Interlocked.Exchange(ref SetData, 0);
+      Message = "Cancelled";
+      OnDisplayExpired(true);
+    }
+
   }
 }

GrasshopperAsyncComponent/GrasshopperAsyncComponent.csproj

@@ -4,7 +4,7 @@
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
     <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
-    <ProjectGuid>{695D2B91-DDB6-416E-8A99-DDE6253DA7AA}</ProjectGuid>
+    <ProjectGuid>{114D5E49-AC13-47F7-A70E-B4289579F4E3}</ProjectGuid>
     <OutputType>Library</OutputType>
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>GrasshopperAsyncComponent</RootNamespace>

GrasshopperAsyncComponentDemo/SampleImplementations/Sample_PrimeCalculatorAsyncComponent.cs

@@ -6,6 +6,7 @@ using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using GrasshopperAsyncComponent;
+using System.Windows.Forms;
 
 namespace GrasshopperAsyncComponentDemo.SampleImplementations
 {
@@ -32,6 +33,15 @@ namespace GrasshopperAsyncComponentDemo.SampleImplementations
       pManager.AddNumberParameter("Output", "O", "The n-th prime number.", GH_ParamAccess.item);
 
     }
+
+    public override void AppendAdditionalMenuItems(ToolStripDropDown menu)
+    {
+      base.AppendAdditionalMenuItems(menu);
+      Menu_AppendItem(menu, "Cancel", (s, e) =>
+      {
+        RequestCancellation();
+      });
+    }
   }
 
   public class PrimeCalculatorWorker : WorkerInstance