Add async File.ReadAll*, File.AppendAll* and File.WriteAll

src/System.IO.FileSystem/ref/System.IO.FileSystem.cs

@@ -91,8 +91,12 @@ public static partial class File
     {
         public static void AppendAllLines(string path, System.Collections.Generic.IEnumerable<string> contents) { }
         public static void AppendAllLines(string path, System.Collections.Generic.IEnumerable<string> contents, System.Text.Encoding encoding) { }
+        public static System.Threading.Tasks.Task AppendAllLinesAsync(string path, System.Collections.Generic.IEnumerable<string> contents, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public static System.Threading.Tasks.Task AppendAllLinesAsync(string path, System.Collections.Generic.IEnumerable<string> contents, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static void AppendAllText(string path, string contents) { }
         public static void AppendAllText(string path, string contents, System.Text.Encoding encoding) { }
+        public static System.Threading.Tasks.Task AppendAllTextAsync(string path, string contents, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public static System.Threading.Tasks.Task AppendAllTextAsync(string path, string contents, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.IO.StreamWriter AppendText(string path) { throw null; }
         public static void Copy(string sourceFileName, string destFileName) { }
         public static void Copy(string sourceFileName, string destFileName, bool overwrite) { }
@@ -119,10 +123,15 @@ public static void Move(string sourceFileName, string destFileName) { }
         public static System.IO.StreamReader OpenText(string path) { throw null; }
         public static System.IO.FileStream OpenWrite(string path) { throw null; }
         public static byte[] ReadAllBytes(string path) { throw null; }
+        public static System.Threading.Tasks.Task<byte[]> ReadAllBytesAsync(string path, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static string[] ReadAllLines(string path) { throw null; }
         public static string[] ReadAllLines(string path, System.Text.Encoding encoding) { throw null; }
+        public static System.Threading.Tasks.Task<string[]> ReadAllLinesAsync(string path, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public static System.Threading.Tasks.Task<string[]> ReadAllLinesAsync(string path, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static string ReadAllText(string path) { throw null; }
         public static string ReadAllText(string path, System.Text.Encoding encoding) { throw null; }
+        public static System.Threading.Tasks.Task<string> ReadAllTextAsync(string path, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public static System.Threading.Tasks.Task<string> ReadAllTextAsync(string path, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.Collections.Generic.IEnumerable<string> ReadLines(string path) { throw null; }
         public static System.Collections.Generic.IEnumerable<string> ReadLines(string path, System.Text.Encoding encoding) { throw null; }
         public static void Replace(string sourceFileName, string destinationFileName, string destinationBackupFileName) { }
@@ -135,12 +144,17 @@ public static void SetLastAccessTimeUtc(string path, System.DateTime lastAccessT
         public static void SetLastWriteTime(string path, System.DateTime lastWriteTime) { }
         public static void SetLastWriteTimeUtc(string path, System.DateTime lastWriteTimeUtc) { }
         public static void WriteAllBytes(string path, byte[] bytes) { }
+        public static System.Threading.Tasks.Task WriteAllBytesAsync(string path, byte[] bytes, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static void WriteAllLines(string path, string[] contents) { }
         public static void WriteAllLines(string path, System.Collections.Generic.IEnumerable<string> contents) { }
         public static void WriteAllLines(string path, string[] contents, System.Text.Encoding encoding) { }
         public static void WriteAllLines(string path, System.Collections.Generic.IEnumerable<string> contents, System.Text.Encoding encoding) { }
+        public static System.Threading.Tasks.Task WriteAllLinesAsync(string path, System.Collections.Generic.IEnumerable<string> contents, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public static System.Threading.Tasks.Task WriteAllLinesAsync(string path, System.Collections.Generic.IEnumerable<string> contents, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static void WriteAllText(string path, string contents) { }
         public static void WriteAllText(string path, string contents, System.Text.Encoding encoding) { }
+        public static System.Threading.Tasks.Task WriteAllTextAsync(string path, string contents, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public static System.Threading.Tasks.Task WriteAllTextAsync(string path, string contents, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
     }
     public sealed partial class FileInfo : System.IO.FileSystemInfo
     {

src/System.IO.FileSystem/src/System.IO.FileSystem.csproj

@@ -371,6 +371,7 @@
     <TargetingPackReference Include="mscorlib" />
   </ItemGroup>
   <ItemGroup>
+    <Reference Include="System.Buffers" />
     <Reference Include="System.Collections" />
     <Reference Include="System.Diagnostics.Contracts" />
     <Reference Include="System.Diagnostics.Debug" />
@@ -379,6 +380,7 @@
     <Reference Include="System.Runtime" />
     <Reference Include="System.Runtime.Extensions" />
     <Reference Include="System.Runtime.InteropServices" />
+    <Reference Include="System.Text.Encoding.Extensions" />
     <Reference Include="System.Threading.Overlapped" />
     <Reference Include="System.Threading.Tasks" />
   </ItemGroup>