Implement HttpRequestStreamReader.ReadToEndAsync

src/Http/WebUtilities/ref/Microsoft.AspNetCore.WebUtilities.netcoreapp.cs

@@ -152,6 +152,8 @@ protected override void Dispose(bool disposing) { }
         public override string ReadLine() { throw null; }
         [System.Diagnostics.DebuggerStepThroughAttribute]
         public override System.Threading.Tasks.Task<string> ReadLineAsync() { throw null; }
+        [System.Diagnostics.DebuggerStepThroughAttribute]
+        public override System.Threading.Tasks.Task<string> ReadToEndAsync() { throw null; }
     }
     public partial class HttpResponseStreamWriter : System.IO.TextWriter
     {

src/Http/WebUtilities/src/HttpRequestStreamReader.cs

@@ -333,7 +333,7 @@ public override async Task<string> ReadLineAsync()
             if (_disposed)
             {
                 throw new ObjectDisposedException(nameof(HttpRequestStreamReader));
-            }              
+            }
 
             StringBuilder sb = null;
             var consumeLineFeed = false;
@@ -528,6 +528,20 @@ private async Task<int> ReadIntoBufferAsync()
             return _charsRead;
         }
 
+        public async override Task<string> ReadToEndAsync()
+        {
+            StringBuilder sb = new StringBuilder(_charsRead - _charBufferIndex);
+            do
+            {
+                int tmpCharPos = _charBufferIndex;
+                sb.Append(_charBuffer, tmpCharPos, _charsRead - tmpCharPos);
+                _charBufferIndex = _charsRead;  // We consumed these characters
+                await ReadIntoBufferAsync().ConfigureAwait(false);
+            } while (_charsRead > 0);
+
+            return sb.ToString();
+        }
+
         private readonly struct ReadLineStepResult
         {
             public static readonly ReadLineStepResult Done = new ReadLineStepResult(true, null);

src/Http/WebUtilities/test/HttpRequestStreamReaderTest.cs

@@ -7,6 +7,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using Xunit;
 
@@ -55,6 +56,22 @@ public static async Task ReadToEndAsync()
             Assert.Equal(5000, result.Length);
         }
 
+        [Fact]
+        public static async Task ReadToEndAsync_Reads_Asynchronously()
+        {
+            // Arrange
+            var stream = new AsyncOnlyStreamWrapper(GetLargeStream());
+            var reader = new HttpRequestStreamReader(stream, Encoding.UTF8);
+            var streamReader = new StreamReader(GetLargeStream());
+            string expected = await streamReader.ReadToEndAsync();
+
+            // Act
+            var actual = await reader.ReadToEndAsync();
+
+            // Assert
+            Assert.Equal(expected, actual);
+        }
+
         [Fact]
         public static void TestRead()
         {
@@ -477,5 +494,84 @@ public static IEnumerable<object[]> ReadLineData()
                  httpRequestStreamReader.ReadLineAsync()
             )};
         }
+
+        private class AsyncOnlyStreamWrapper : Stream
+        {
+            private readonly Stream _inner;
+
+            public AsyncOnlyStreamWrapper(Stream inner)
+            {
+                _inner = inner;
+            }
+
+            public override bool CanRead => _inner.CanRead;
+
+            public override bool CanSeek => _inner.CanSeek;
+
+            public override bool CanWrite => _inner.CanWrite;
+
+            public override long Length => _inner.Length;
+
+            public override long Position
+            {
+                get => _inner.Position;
+                set => _inner.Position = value;
+            }
+
+            public override void Flush()
+            {
+                throw SyncOperationForbiddenException();
+            }
+
+            public override Task FlushAsync(CancellationToken cancellationToken)
+            {
+                return _inner.FlushAsync(cancellationToken);
+            }
+
+            public override int Read(byte[] buffer, int offset, int count)
+            {
+                throw SyncOperationForbiddenException();
+            }
+
+            public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+            {
+                return _inner.ReadAsync(buffer, offset, count, cancellationToken);
+            }
+
+            public override long Seek(long offset, SeekOrigin origin)
+            {
+                return _inner.Seek(offset, origin);
+            }
+
+            public override void SetLength(long value)
+            {
+                _inner.SetLength(value);
+            }
+
+            public override void Write(byte[] buffer, int offset, int count)
+            {
+                throw SyncOperationForbiddenException();
+            }
+
+            public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+            {
+                return _inner.WriteAsync(buffer, offset, count, cancellationToken);
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                _inner.Dispose();
+            }
+
+            public override ValueTask DisposeAsync()
+            {
+                return _inner.DisposeAsync();
+            }
+
+            private Exception SyncOperationForbiddenException()
+            {
+                return new InvalidOperationException("The stream cannot be accessed synchronously");
+            }
+        }
     }
 }