Set Runspaces to use STA when running in Windows PowerShell (PowerShell#769)

Update PSStandard dependency (PowerShell#771)

Author: rjmholt

src/PowerShellEditorServices/PowerShellEditorServices.csproj

@@ -13,7 +13,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.CSharp" Version="4.5.0" />
-    <PackageReference Include="PowerShellStandard.Library" Version="5.1.0-preview-06" PrivateAssets="All"/>
+    <PackageReference Include="PowerShellStandard.Library" Version="5.1.0-RC1" PrivateAssets="All"/>
     <PackageReference Include="UnixConsoleEcho" Version="0.1.0" />
     <PackageReference Include="Serilog" Version="2.7.1" />
     <PackageReference Include="Serilog.Sinks.Console" Version="3.1.1" />

src/PowerShellEditorServices/Session/InvocationEventQueue.cs

@@ -225,11 +225,6 @@ private void OnInvokerUnsubscribed(object sender, PSEventUnsubscribedEventArgs e
             CreateInvocationSubscriber();
         }
 
-        private void OnInvokerUnsubscribed(object sender, PSEventArgs e)
-        {
-            CreateInvocationSubscriber();
-        }
-
         private void SetSubscriberExecutionThreadWithReflection(PSEventSubscriber subscriber)
         {
             // We need to create the PowerShell object in the same thread so we can get a nested

src/PowerShellEditorServices/Session/PowerShellContext.cs

@@ -8,10 +8,12 @@
 using System.Collections.ObjectModel;
 using System.Globalization;
 using System.IO;
+using System.Runtime.InteropServices;
 using System.Linq;
 using System.Management.Automation.Host;
 using System.Management.Automation.Remoting;
 using System.Management.Automation.Runspaces;
+using System.Reflection;
 using System.Text;
 using System.Text.RegularExpressions;
 using System.Threading;
@@ -32,6 +34,21 @@ namespace Microsoft.PowerShell.EditorServices
     /// </summary>
     public class PowerShellContext : IDisposable, IHostSupportsInteractiveSession
     {
+        private const string DotNetFrameworkDescription = ".NET Framework";
+
+        private static readonly Action<Runspace, ApartmentState> s_runspaceApartmentStateSetter;
+
+        static PowerShellContext()
+        {
+            // PowerShell ApartmentState APIs aren't available in PSStandard, so we need to use reflection
+            if (RuntimeInformation.FrameworkDescription.Equals(DotNetFrameworkDescription))
+            {
+                MethodInfo setterInfo = typeof(Runspace).GetProperty("ApartmentState").GetSetMethod();
+                Delegate setter = Delegate.CreateDelegate(typeof(Action<Runspace, ApartmentState>), firstArgument: null, method: setterInfo);
+                s_runspaceApartmentStateSetter = (Action<Runspace, ApartmentState>)setter;
+            }
+        }
+
         #region Fields
 
         private readonly SemaphoreSlim resumeRequestHandle = AsyncUtils.CreateSimpleLockingSemaphore();
@@ -175,6 +192,14 @@ public static Runspace CreateRunspace(PSHost psHost)
             }
 
             Runspace runspace = RunspaceFactory.CreateRunspace(psHost, initialSessionState);
+
+            // Windows PowerShell must be hosted in STA mode
+            // This must be set on the runspace *before* it is opened
+            if (RuntimeInformation.FrameworkDescription.Equals(DotNetFrameworkDescription))
+            {
+                s_runspaceApartmentStateSetter(runspace, ApartmentState.STA);
+            }
+
             runspace.ThreadOptions = PSThreadOptions.ReuseThread;
             runspace.Open();