Added cached API check for SDK 17763

Author: Sergio0694

Microsoft.Toolkit.Uwp/Extensions/DispatcherQueueExtensions.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Threading.Tasks;
+using Windows.Foundation.Metadata;
 using Windows.System;
 
 #nullable enable
@@ -15,6 +16,11 @@ namespace Microsoft.Toolkit.Uwp.Extensions
     /// </summary>
     public static class DispatcherQueueExtensions
     {
+        /// <summary>
+        /// Indicates whether or not <see cref="DispatcherQueue.HasThreadAccess"/> is available.
+        /// </summary>
+        private static readonly bool IsHasThreadAccessPropertyAvailable = ApiInformation.IsMethodPresent("Windows.System.DispatcherQueue", "HasThreadAccess");
+
         /// <summary>
         /// Invokes a given function on the target <see cref="DispatcherQueue"/> and returns a
         /// <see cref="Task"/> that completes when the invocation of the function is completed.
@@ -29,7 +35,7 @@ public static Task EnqueueAsync(this DispatcherQueue dispatcher, Action function
             // Run the function directly when we have thread access.
             // Also reuse Task.CompletedTask in case of success,
             // to skip an unnecessary heap allocation for every invocation.
-            if (dispatcher.HasThreadAccess)
+            if (IsHasThreadAccessPropertyAvailable && dispatcher.HasThreadAccess)
             {
                 try
                 {
@@ -82,7 +88,7 @@ static Task TryEnqueueAsync(DispatcherQueue dispatcher, Action function, Dispatc
         /// <remarks>If the current thread has access to <paramref name="dispatcher"/>, <paramref name="function"/> will be invoked directly.</remarks>
         public static Task<T> EnqueueAsync<T>(this DispatcherQueue dispatcher, Func<T> function, DispatcherQueuePriority priority = DispatcherQueuePriority.Normal)
         {
-            if (dispatcher.HasThreadAccess)
+            if (IsHasThreadAccessPropertyAvailable && dispatcher.HasThreadAccess)
             {
                 try
                 {
@@ -134,7 +140,7 @@ public static Task EnqueueAsync(this DispatcherQueue dispatcher, Func<Task> func
             // We don't use ConfigureAwait(false) in this case, in order
             // to let the caller continue its execution on the same thread
             // after awaiting the task returned by this function.
-            if (dispatcher.HasThreadAccess)
+            if (IsHasThreadAccessPropertyAvailable && dispatcher.HasThreadAccess)
             {
                 try
                 {
@@ -197,7 +203,7 @@ static Task TryEnqueueAsync(DispatcherQueue dispatcher, Func<Task> function, Dis
         /// <remarks>If the current thread has access to <paramref name="dispatcher"/>, <paramref name="function"/> will be invoked directly.</remarks>
         public static Task<T> EnqueueAsync<T>(this DispatcherQueue dispatcher, Func<Task<T>> function, DispatcherQueuePriority priority = DispatcherQueuePriority.Normal)
         {
-            if (dispatcher.HasThreadAccess)
+            if (IsHasThreadAccessPropertyAvailable && dispatcher.HasThreadAccess)
             {
                 try
                 {