Use NullFileProvider from FileSystem

src/Microsoft.AspNetCore.Hosting/Internal/NullFileProvider.cs

@@ -1,82 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.IO;
-using Microsoft.Extensions.FileProviders;
-using Microsoft.Extensions.Primitives;
-
-namespace Microsoft.AspNetCore.Hosting.Internal
-{
-    internal class NullFileProvider : IFileProvider
-    {
-        public IDirectoryContents GetDirectoryContents(string subpath)
-        {
-            return new NullDirectoryContents();
-        }
-
-        public IFileInfo GetFileInfo(string subpath)
-        {
-            return new NullFileInfo(subpath);
-        }
-
-        public IChangeToken Watch(string filter)
-        {
-            return new NullChangeToken();
-        }
-
-        private class NullDirectoryContents : IDirectoryContents
-        {
-            public bool Exists => false;
-
-            public IEnumerator<IFileInfo> GetEnumerator()
-            {
-                yield break;
-            }
-
-            IEnumerator IEnumerable.GetEnumerator()
-            {
-                return GetEnumerator();
-            }
-        }
-
-        internal class NullFileInfo : IFileInfo
-        {
-            public NullFileInfo(string name)
-            {
-                Name = name;
-            }
-
-            public bool Exists => false;
-
-            public bool IsDirectory => false;
-
-            public DateTimeOffset LastModified => DateTimeOffset.MinValue;
-
-            public long Length => -1;
-
-            public string Name { get; }
-
-            public string PhysicalPath => null;
-
-            public Stream CreateReadStream()
-            {
-                throw new FileNotFoundException(string.Format($"{nameof(NullFileProvider)} does not support reading files.", Name));
-            }
-        }
-
-        private class NullChangeToken : IChangeToken
-        {
-            public bool HasChanged => false;
-
-            public bool ActiveChangeCallbacks => false;
-
-            public IDisposable RegisterChangeCallback(Action<object> callback, object state)
-            {
-                throw new NotSupportedException($"{nameof(NullFileProvider)} does not support registering change notifications.");
-            }
-        }
-    }
-}