Add FileStreamOptions overloads

src/libraries/System.IO.FileSystem/tests/File/Open.cs

@@ -42,6 +42,24 @@ protected override FileStream CreateFileStream(string path, FileMode mode, FileA
         }
     }
 
+    public class File_Open_str_fm_fa_fs_buffer_fo : FileStream_ctor_str_fm_fa_fs_buffer_fo
+    {
+        protected override FileStream CreateFileStream(string path, FileMode mode)
+        {
+            return File.Open(path, new FileStreamOptions { Mode = mode, Access = (mode == FileMode.Append ? FileAccess.Write : FileAccess.ReadWrite) });
+        }
+
+        protected override FileStream CreateFileStream(string path, FileMode mode, FileAccess access)
+        {
+            return File.Open(path, new FileStreamOptions { Mode = mode, Access = access });
+        }
+
+        protected override FileStream CreateFileStream(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, FileOptions options)
+        {
+            return File.Open(path, new FileStreamOptions { Mode = mode, Access = access, Share = share, Options = options, BufferSize = bufferSize });
+        }
+    }
+
     public class File_OpenSpecial : FileStream_ctor_str_fm_fa_fs
     {
         protected override FileStream CreateFileStream(string path, FileMode mode, FileAccess access)

src/libraries/System.IO.FileSystem/tests/FileInfo/Open.cs

@@ -74,6 +74,24 @@ protected override FileStream CreateFileStream(string path, FileMode mode, FileA
         }
     }
 
+    public class FileInfo_Open_fm_fa_fs_buffer_fo : FileStream_ctor_str_fm_fa_fs_buffer_fo
+    {
+        protected override FileStream CreateFileStream(string path, FileMode mode)
+        {
+            return new FileInfo(path).Open(new FileStreamOptions { Mode = mode, Access = (mode == FileMode.Append ? FileAccess.Write : FileAccess.ReadWrite) });
+        }
+
+        protected override FileStream CreateFileStream(string path, FileMode mode, FileAccess access)
+        {
+            return new FileInfo(path).Open(new FileStreamOptions { Mode = mode, Access = access });
+        }
+
+        protected override FileStream CreateFileStream(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, FileOptions options)
+        {
+            return new FileInfo(path).Open(new FileStreamOptions { Mode = mode, Access = access, Share = share, Options = options, BufferSize = bufferSize });
+        }
+    }
+
     public class FileInfo_OpenSpecial : FileStream_ctor_str_fm_fa_fs
     {
         protected override FileStream CreateFileStream(string path, FileMode mode, FileAccess access)

src/libraries/System.IO/tests/StreamReader/StreamReader.StringCtorTests.cs

@@ -14,21 +14,29 @@ public class StreamReader_StringCtorTests
         public static void NullArgs_ThrowsArgumentNullException()
         {
             AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamReader((string)null));
-            AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamReader((string)null, null));
+            AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamReader((string)null, (FileStreamOptions)null));
+            AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamReader((string)null, (Encoding)null));
             AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamReader((string)null, null, true));
+            AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamReader((string)null, null, true, null));
             AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamReader((string)null, null, true, -1));
-            AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamReader("", null));
+            AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamReader("", (Encoding)null));
             AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamReader("", null, true));
+            AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamReader("", null, true, null));
             AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamReader("", null, true, -1));
+            AssertExtensions.Throws<ArgumentNullException>("options", () => new StreamReader("path", (FileStreamOptions)null));
+            AssertExtensions.Throws<ArgumentNullException>("options", () => new StreamReader("path", Encoding.UTF8, true, null));
+
         }
 
         [Fact]
         public static void EmptyPath_ThrowsArgumentException()
         {
             // No argument name for the empty path exception
             AssertExtensions.Throws<ArgumentException>(null, () => new StreamReader(""));
+            AssertExtensions.Throws<ArgumentException>(null, () => new StreamReader("", new FileStreamOptions()));
             AssertExtensions.Throws<ArgumentException>(null, () => new StreamReader("", Encoding.UTF8));
             AssertExtensions.Throws<ArgumentException>(null, () => new StreamReader("", Encoding.UTF8, true));
+            AssertExtensions.Throws<ArgumentException>(null, () => new StreamReader("", Encoding.UTF8, true, new FileStreamOptions()));
             AssertExtensions.Throws<ArgumentException>(null, () => new StreamReader("", Encoding.UTF8, true, -1));
         }
 

src/libraries/System.IO/tests/StreamWriter/StreamWriter.StringCtorTests.cs

@@ -15,12 +15,15 @@ public class StreamWriter_StringCtorTests
         public static void NullArgs_ThrowsArgumentNullException()
         {
             AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamWriter((string)null));
+            AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamWriter((string)null, null));
             AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamWriter((string)null, true));
             AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamWriter((string)null, true, null));
             AssertExtensions.Throws<ArgumentNullException>("path", () => new StreamWriter((string)null, true, null, -1));
             AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamWriter("path", true, null));
+            AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamWriter("path", null, null));
             AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamWriter("path", true, null, -1));
             AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamWriter("", true, null));
+            AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamWriter("", null, null));
             AssertExtensions.Throws<ArgumentNullException>("encoding", () => new StreamWriter("", true, null, -1));
         }
 
@@ -29,8 +32,10 @@ public static void EmptyPath_ThrowsArgumentException()
         {
             // No argument name for the empty path exception
             AssertExtensions.Throws<ArgumentException>(null, () => new StreamWriter(""));
+            AssertExtensions.Throws<ArgumentException>(null, () => new StreamWriter("", new FileStreamOptions()));
             AssertExtensions.Throws<ArgumentException>(null, () => new StreamWriter("", true));
             AssertExtensions.Throws<ArgumentException>(null, () => new StreamWriter("", true, Encoding.UTF8));
+            AssertExtensions.Throws<ArgumentException>(null, () => new StreamWriter("", Encoding.UTF8, new FileStreamOptions()));
             AssertExtensions.Throws<ArgumentException>(null, () => new StreamWriter("", true, Encoding.UTF8, -1));
         }
 

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -407,9 +407,11 @@
     <Compile Include="$(MSBuildThisFileDirectory)System\IO\EnumerationOptions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\IO\EndOfStreamException.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\IO\File.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\File.netcoreapp.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileAccess.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileAttributes.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileInfo.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileInfo.netcoreapp.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileLoadException.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileMode.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\IO\FileNotFoundException.cs" />

src/libraries/System.Private.CoreLib/src/System/IO/File.cs

@@ -21,7 +21,7 @@ namespace System.IO
 {
     // Class for creating FileStream objects, and some basic file management
     // routines such as Delete, etc.
-    public static class File
+    public static partial class File
     {
         private const int MaxByteArrayLength = 0x7FFFFFC7;
         private static Encoding? s_UTF8NoBOM;
@@ -262,8 +262,7 @@ public static FileStream OpenRead(string path)
 
         public static FileStream OpenWrite(string path)
         {
-            return new FileStream(path, FileMode.OpenOrCreate,
-                                  FileAccess.Write, FileShare.None);
+            return new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write, FileShare.None);
         }
 
         public static string ReadAllText(string path)

src/libraries/System.Private.CoreLib/src/System/IO/File.netcoreapp.cs

@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.IO
+{
+    public static partial class File
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="System.IO.FileStream" /> class with the specified path, creation mode, read/write and sharing permission, the access other FileStreams can have to the same file, the buffer size, additional file options and the allocation size.
+        /// </summary>
+        /// <remarks><see cref="System.IO.FileStream(string,System.IO.FileStreamOptions)"/> for information about exceptions.</remarks>
+        public static FileStream Open(string path, FileStreamOptions options) => new FileStream(path, options);
+    }
+}

src/libraries/System.Private.CoreLib/src/System/IO/FileInfo.cs

@@ -122,7 +122,7 @@ public FileStream Open(FileMode mode, FileAccess access, FileShare share)
             => new FileStream(NormalizedPath, mode, access, share);
 
         public FileStream OpenRead()
-            => new FileStream(NormalizedPath, FileMode.Open, FileAccess.Read, FileShare.Read, 4096, false);
+            => new FileStream(NormalizedPath, FileMode.Open, FileAccess.Read, FileShare.Read, File.DefaultBufferSize, false);
 
         public FileStream OpenWrite()
             => new FileStream(NormalizedPath, FileMode.OpenOrCreate, FileAccess.Write, FileShare.None);

src/libraries/System.Private.CoreLib/src/System/IO/FileInfo.netcoreapp.cs

@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.IO
+{
+    public sealed partial class FileInfo : FileSystemInfo
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="System.IO.FileStream" /> class with the specified creation mode, read/write and sharing permission, the access other FileStreams can have to the same file, the buffer size, additional file options and the allocation size.
+        /// </summary>
+        /// <remarks><see cref="System.IO.FileStream(string,System.IO.FileStreamOptions)"/> for information about exceptions.</remarks>
+        public FileStream Open(FileStreamOptions options) => File.Open(NormalizedPath, options);
+    }
+}

src/libraries/System.Private.CoreLib/src/System/IO/StreamReader.cs

@@ -193,23 +193,47 @@ public StreamReader(string path, Encoding encoding, bool detectEncodingFromByteO
         {
         }
 
-        public StreamReader(string path, Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize) :
-            this(ValidateArgsAndOpenPath(path, encoding, bufferSize), encoding, detectEncodingFromByteOrderMarks, bufferSize, leaveOpen: false)
+        public StreamReader(string path, Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize)
+            : this(ValidateArgsAndOpenPath(path, encoding, bufferSize), encoding, detectEncodingFromByteOrderMarks, bufferSize, leaveOpen: false)
         {
         }
 
+        public StreamReader(string path, FileStreamOptions options)
+            : this(path, Encoding.UTF8, true, options)
+        {
+        }
+
+        public StreamReader(string path, Encoding encoding, bool detectEncodingFromByteOrderMarks, FileStreamOptions options)
+            : this(ValidateArgsAndOpenPath(path, encoding, options), encoding, detectEncodingFromByteOrderMarks, DefaultBufferSize)
+        {
+        }
+
+        private static Stream ValidateArgsAndOpenPath(string path, Encoding encoding, FileStreamOptions options)
+        {
+            ValidateArgs(path, encoding);
+            if (options == null)
+                throw new ArgumentNullException(nameof(options));
+
+            return new FileStream(path, options);
+        }
+
         private static Stream ValidateArgsAndOpenPath(string path, Encoding encoding, int bufferSize)
+        {
+            ValidateArgs(path, encoding);
+            if (bufferSize <= 0)
+                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
+
+            return new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, DefaultFileStreamBufferSize);
+        }
+
+        private static void ValidateArgs(string path, Encoding encoding)
         {
             if (path == null)
                 throw new ArgumentNullException(nameof(path));
             if (encoding == null)
                 throw new ArgumentNullException(nameof(encoding));
             if (path.Length == 0)
                 throw new ArgumentException(SR.Argument_EmptyPath);
-            if (bufferSize <= 0)
-                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
-
-            return new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, DefaultFileStreamBufferSize, FileOptions.SequentialScan);
         }
 
         public override void Close()

src/libraries/System.Private.CoreLib/src/System/IO/StreamWriter.cs

@@ -154,18 +154,42 @@ public StreamWriter(string path, bool append, Encoding encoding)
         {
         }
 
+        public StreamWriter(string path, FileStreamOptions options)
+            : this(path, UTF8NoBOM, options)
+        {
+        }
+
+        public StreamWriter(string path, Encoding encoding, FileStreamOptions options)
+            : this(ValidateArgsAndOpenPath(path, encoding, options), encoding, DefaultFileStreamBufferSize)
+        {
+        }
+
+        private static Stream ValidateArgsAndOpenPath(string path, Encoding encoding, FileStreamOptions options)
+        {
+            ValidateArgs(path, encoding);
+            if (options == null)
+                throw new ArgumentNullException(nameof(options));
+
+            return new FileStream(path, options);
+        }
+
         private static Stream ValidateArgsAndOpenPath(string path, bool append, Encoding encoding, int bufferSize)
+        {
+            ValidateArgs(path, encoding);
+            if (bufferSize <= 0)
+                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
+
+            return new FileStream(path, append ? FileMode.Append : FileMode.Create, FileAccess.Write, FileShare.Read, DefaultFileStreamBufferSize);
+        }
+
+        private static void ValidateArgs(string path, Encoding encoding)
         {
             if (path == null)
                 throw new ArgumentNullException(nameof(path));
             if (encoding == null)
                 throw new ArgumentNullException(nameof(encoding));
             if (path.Length == 0)
                 throw new ArgumentException(SR.Argument_EmptyPath);
-            if (bufferSize <= 0)
-                throw new ArgumentOutOfRangeException(nameof(bufferSize), SR.ArgumentOutOfRange_NeedPosNum);
-
-            return new FileStream(path, append ? FileMode.Append : FileMode.Create, FileAccess.Write, FileShare.Read, DefaultFileStreamBufferSize, FileOptions.SequentialScan);
         }
 
         public override void Close()

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -7564,6 +7564,7 @@ public static partial class File
         public static System.IO.FileStream Open(string path, System.IO.FileMode mode) { throw null; }
         public static System.IO.FileStream Open(string path, System.IO.FileMode mode, System.IO.FileAccess access) { throw null; }
         public static System.IO.FileStream Open(string path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share) { throw null; }
+        public static System.IO.FileStream Open(string path, System.IO.FileStreamOptions options) { throw null; }
         public static System.IO.FileStream OpenRead(string path) { throw null; }
         public static System.IO.StreamReader OpenText(string path) { throw null; }
         public static System.IO.FileStream OpenWrite(string path) { throw null; }
@@ -7625,6 +7626,7 @@ public sealed partial class FileInfo : System.IO.FileSystemInfo
         public System.IO.FileStream Open(System.IO.FileMode mode) { throw null; }
         public System.IO.FileStream Open(System.IO.FileMode mode, System.IO.FileAccess access) { throw null; }
         public System.IO.FileStream Open(System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share) { throw null; }
+        public System.IO.FileStream Open(System.IO.FileStreamOptions options) { throw null; }
         public System.IO.FileStream OpenRead() { throw null; }
         public System.IO.StreamReader OpenText() { throw null; }
         public System.IO.FileStream OpenWrite() { throw null; }
@@ -7821,10 +7823,12 @@ public partial class StreamReader : System.IO.TextReader
         public StreamReader(System.IO.Stream stream, System.Text.Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize) { }
         public StreamReader(System.IO.Stream stream, System.Text.Encoding? encoding = null, bool detectEncodingFromByteOrderMarks = true, int bufferSize = -1, bool leaveOpen = false) { }
         public StreamReader(string path) { }
+        public StreamReader(string path, System.IO.FileStreamOptions options) { }
         public StreamReader(string path, bool detectEncodingFromByteOrderMarks) { }
         public StreamReader(string path, System.Text.Encoding encoding) { }
         public StreamReader(string path, System.Text.Encoding encoding, bool detectEncodingFromByteOrderMarks) { }
         public StreamReader(string path, System.Text.Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize) { }
+        public StreamReader(string path, System.Text.Encoding encoding, bool detectEncodingFromByteOrderMarks, System.IO.FileStreamOptions options) { }
         public virtual System.IO.Stream BaseStream { get { throw null; } }
         public virtual System.Text.Encoding CurrentEncoding { get { throw null; } }
         public bool EndOfStream { get { throw null; } }
@@ -7854,9 +7858,11 @@ public partial class StreamWriter : System.IO.TextWriter
         public StreamWriter(System.IO.Stream stream, System.Text.Encoding encoding, int bufferSize) { }
         public StreamWriter(System.IO.Stream stream, System.Text.Encoding? encoding = null, int bufferSize = -1, bool leaveOpen = false) { }
         public StreamWriter(string path) { }
+        public StreamWriter(string path, System.IO.FileStreamOptions options) { }
         public StreamWriter(string path, bool append) { }
         public StreamWriter(string path, bool append, System.Text.Encoding encoding) { }
         public StreamWriter(string path, bool append, System.Text.Encoding encoding, int bufferSize) { }
+        public StreamWriter(string path, System.Text.Encoding encoding, System.IO.FileStreamOptions options) { }
         public virtual bool AutoFlush { get { throw null; } set { } }
         public virtual System.IO.Stream BaseStream { get { throw null; } }
         public override System.Text.Encoding Encoding { get { throw null; } }