XmlReader.Read shouldn't throw AggregateException (#25681)

* XmlReader.Read shouldn't throw AggregateException

* Remove unnecessary uses of Task.Result

* Address feedback

* Test is skipped on .Net Framework

Author: svick

src/System.Private.Xml/src/System/Xml/Core/XmlTextReaderImpl.cs

@@ -9,6 +9,7 @@
 using System.Globalization;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
 
 namespace System.Xml
 {
@@ -624,9 +625,8 @@ private void FinishInitUriString()
             {
                 //this will be hit when user create a XmlReader by setting Async, but the first call is Read() instead of ReadAsync(), 
                 //then we still should create an async stream here. And wait for the method finish.
-                System.Threading.Tasks.Task<object> t = _laterInitParam.inputUriResolver.GetEntityAsync(_laterInitParam.inputbaseUri, string.Empty, typeof(Stream));
-                t.Wait();
-                stream = (Stream)t.Result;
+                Task<object> t = _laterInitParam.inputUriResolver.GetEntityAsync(_laterInitParam.inputbaseUri, string.Empty, typeof(Stream));
+                stream = (Stream)t.GetAwaiter().GetResult();
             }
             else
             {

src/System.Private.Xml/src/System/Xml/Core/XmlTextReaderImplAsync.cs

@@ -367,8 +367,8 @@ public override async Task SkipAsync()
 
         private async Task<int> ReadContentAsBase64_AsyncHelper(Task<bool> task, byte[] buffer, int index, int count)
         {
-            await task.ConfigureAwait(false);
-            if (!task.Result)
+            bool result = await task.ConfigureAwait(false);
+            if (!result)
             {
                 return 0;
             }
@@ -514,8 +514,8 @@ public override async Task<int> ReadContentAsBinHexAsync(byte[] buffer, int inde
 
         private async Task<int> ReadElementContentAsBase64Async_Helper(Task<bool> task, byte[] buffer, int index, int count)
         {
-            await task.ConfigureAwait(false);
-            if (!task.Result)
+            bool result = await task.ConfigureAwait(false);
+            if (!result)
             {
                 return 0;
             }

src/System.Private.Xml/tests/XmlReader/Tests/AsyncReaderLateInitTests.cs

@@ -39,10 +39,10 @@ public static void ReadAsyncAfterInitializationWithStreamDoesNotThrow()
             }
         }
 
-        [Fact]
-        public static void ReadAfterInitializationWithStreamOnAsyncReaderDoesNotThrow()
+        [Theory, InlineData(true), InlineData(false)]
+        public static void ReadAfterInitializationWithStreamOnAsyncReaderDoesNotThrow(bool async)
         {
-            using (XmlReader reader = XmlReader.Create(GetDummyXmlStream(), new XmlReaderSettings() { Async = true }))
+            using (XmlReader reader = XmlReader.Create(GetDummyXmlStream(), new XmlReaderSettings() { Async = async }))
             {
                 reader.Read();
             }
@@ -57,10 +57,10 @@ public static void ReadAsyncAfterInitializationWithTextReaderDoesNotThrow()
             }
         }
 
-        [Fact]
-        public static void ReadAfterInitializationWithTextReaderOnAsyncReaderDoesNotThrow()
+        [Theory, InlineData(true), InlineData(false)]
+        public static void ReadAfterInitializationWithTextReaderOnAsyncReaderDoesNotThrow(bool async)
         {
-            using (XmlReader reader = XmlReader.Create(GetDummyXmlTextReader(), new XmlReaderSettings() { Async = true }))
+            using (XmlReader reader = XmlReader.Create(GetDummyXmlTextReader(), new XmlReaderSettings() { Async = async }))
             {
                 reader.Read();
             }
@@ -75,14 +75,19 @@ public static void ReadAsyncAfterInitializationWithUriThrows()
             }
         }
 
-        [Fact]
+        [Fact, SkipOnTargetFramework(TargetFrameworkMonikers.NetFramework, ".Net Framework throws AggregateException")]
         public static void ReadAfterInitializationWithUriOnAsyncReaderTrows()
         {
             using (XmlReader reader = XmlReader.Create("http://test.test/test.html", new XmlReaderSettings() { Async = true }))
             {
-                AggregateException ae = Assert.Throws<System.AggregateException>(() => reader.Read());
-                Assert.Equal(typeof(System.Net.WebException), ae.InnerException.GetType());
+                Assert.Throws<System.Net.WebException>(() => reader.Read());
             }
         }
+
+        [Fact]
+        public static void InitializationWithUriOnNonAsyncReaderTrows()
+        {
+            Assert.Throws<System.Net.WebException>(() => XmlReader.Create("http://test.test/test.html", new XmlReaderSettings() { Async = false }));
+        }
     }
 }