Use reflection to call into the right helper.

src/VisualStudio/Core/Def/Experimentation/IVsExperimentationService.cs

@@ -20,11 +20,14 @@ internal interface IVsExperimentationService
         [DispId(1610678272)]
         Array AllEnabledCachedFlights { get; }
 
-        [return: ComAliasName("EnvDTE.ULONG_PTR")]
-        uint AdviseFlightEvents(IVsFlightEvents flightSink);
+        void Start();
+
         bool IsCachedFlightEnabled([ComAliasName("OLE.LPCOLESTR")] string flightName);
+
         IVsTask IsFlightEnabledAsync([ComAliasName("OLE.LPCOLESTR")] string flightName);
-        void Start();
+
+        [return: ComAliasName("EnvDTE.ULONG_PTR")]
+        uint AdviseFlightEvents(IVsFlightEvents flightSink);
         void UnadviseFlightEvents([ComAliasName("EnvDTE.ULONG_PTR")] uint cookie);
     }
 

src/VisualStudio/Core/Def/Experimentation/VisualStudioExperimentationService.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System.Composition;
+using System.Reflection;
 using Microsoft.CodeAnalysis.Experiments;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.Internal.VisualStudio.Shell.Interop;
@@ -11,7 +12,8 @@ namespace Microsoft.VisualStudio.LanguageServices.Experimentation
     [ExportWorkspaceService(typeof(IExperimentationService), ServiceLayer.Host), Shared]
     internal class VisualStudioExperimentationService : IExperimentationService
     {
-        private readonly IVsExperimentationService _experimentationServiceOpt;
+        private readonly object _experimentationServiceOpt;
+        private readonly MethodInfo _isCachedFlightEnabledInfo;
 
         [ImportingConstructor]
         public VisualStudioExperimentationService(
@@ -19,7 +21,12 @@ internal class VisualStudioExperimentationService : IExperimentationService
         {
             try
             {
-                _experimentationServiceOpt = (IVsExperimentationService)serviceProvider.GetService(typeof(SVsServiceProvider));
+                _experimentationServiceOpt = serviceProvider.GetService(typeof(SVsExperimentationService));
+                if (_experimentationServiceOpt != null)
+                {
+                    _isCachedFlightEnabledInfo = _experimentationServiceOpt.GetType().GetMethod(
+                        "IsCachedFlightEnabled", BindingFlags.Public | BindingFlags.Instance);
+                }
             }
             catch
             {
@@ -27,6 +34,20 @@ internal class VisualStudioExperimentationService : IExperimentationService
         }
 
         public bool IsExperimentEnabled(string experimentName)
-            => _experimentationServiceOpt?.IsCachedFlightEnabled(experimentName) ?? false;
+        {
+            if (_isCachedFlightEnabledInfo != null)
+            {
+                try
+                {
+                    return (bool)_isCachedFlightEnabledInfo.Invoke(_experimentationServiceOpt, new object[] { experimentName });
+                }
+                catch
+                {
+
+                }
+            }
+
+            return false;
+        }
     }
 }
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