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Remove isAsync flag validation from FileStream constructors #123761

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Merged
adamsitnik merged 5 commits into from
Jan 30, 2026
+27 −44
Merged

Remove isAsync flag validation from FileStream constructors #123761

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b669408
Initial plan
Copilot Jan 29, 2026
4b253cc
Remove isAsync flag validation from FileStream constructors
Copilot Jan 29, 2026
0d106df
Fix unused parameter issue in ValidateHandle
Copilot Jan 29, 2026
9e8d786
Add assertions to verify FileStream uses handle's IsAsync value
Copilot Jan 29, 2026
7fb921f
Address review feedback: convert test to theory and add async I/O ver…
Copilot Jan 29, 2026
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6 changes: 0 additions & 6 deletions src/libraries/System.Private.CoreLib/src/Resources/Strings.resx
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Original file line number Diff line number Diff line change
Expand Up @@ -403,12 +403,6 @@
<data name="Arg_GuidArrayCtor" xml:space="preserve">
<value>Byte array for Guid must be exactly {0} bytes long.</value>
</data>
<data name="Arg_HandleNotAsync" xml:space="preserve">
<value>Handle does not support asynchronous operations. The parameters to the FileStream constructor may need to be changed to indicate that the handle was opened synchronously (that is, it was not opened for overlapped I/O).</value>
</data>
<data name="Arg_HandleNotSync" xml:space="preserve">
<value>Handle does not support synchronous operations. The parameters to the FileStream constructor may need to be changed to indicate that the handle was opened asynchronously (that is, it was opened explicitly for overlapped I/O).</value>
</data>
<data name="Arg_HexBinaryStylesNotSupported" xml:space="preserve">
<value>The number styles AllowHexSpecifier and AllowBinarySpecifier are not supported on floating point data types.</value>
</data>
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13 changes: 2 additions & 11 deletions src/libraries/System.Private.CoreLib/src/System/IO/FileStream.cs
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Expand Up @@ -48,7 +48,7 @@ public FileStream(IntPtr handle, FileAccess access, bool ownsHandle, int bufferS
{
ValidateHandle(safeHandle, access, bufferSize, isAsync);

_strategy = FileStreamHelpers.ChooseStrategy(this, safeHandle, access, bufferSize, isAsync);
_strategy = FileStreamHelpers.ChooseStrategy(this, safeHandle, access, bufferSize, safeHandle.IsAsync);
}
catch
{
Expand Down Expand Up @@ -87,15 +87,6 @@ private static void ValidateHandle(SafeFileHandle handle, FileAccess access, int
private static void ValidateHandle(SafeFileHandle handle, FileAccess access, int bufferSize, bool isAsync)
{
ValidateHandle(handle, access, bufferSize);

if (isAsync && !handle.IsAsync)
{
ThrowHelper.ThrowArgumentException_HandleNotAsync(nameof(handle));
}
else if (!isAsync && handle.IsAsync)
{
ThrowHelper.ThrowArgumentException_HandleNotSync(nameof(handle));
}
}

public FileStream(SafeFileHandle handle, FileAccess access)
Expand All @@ -114,7 +105,7 @@ public FileStream(SafeFileHandle handle, FileAccess access, int bufferSize, bool
{
ValidateHandle(handle, access, bufferSize, isAsync);

_strategy = FileStreamHelpers.ChooseStrategy(this, handle, access, bufferSize, isAsync);
_strategy = FileStreamHelpers.ChooseStrategy(this, handle, access, bufferSize, handle.IsAsync);
}

public FileStream(string path, FileMode mode)
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12 changes: 0 additions & 12 deletions src/libraries/System.Private.CoreLib/src/System/ThrowHelper.cs
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Expand Up @@ -335,18 +335,6 @@ internal static void ThrowArgumentException(ExceptionResource resource, Exceptio
throw GetArgumentException(resource, argument);
}

[DoesNotReturn]
internal static void ThrowArgumentException_HandleNotSync(string paramName)
{
throw new ArgumentException(SR.Arg_HandleNotSync, paramName);
}

[DoesNotReturn]
internal static void ThrowArgumentException_HandleNotAsync(string paramName)
{
throw new ArgumentException(SR.Arg_HandleNotAsync, paramName);
}

[DoesNotReturn]
internal static void ThrowArgumentNullException(ExceptionArgument argument)
{
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10 changes: 7 additions & 3 deletions ...es/System.Runtime/tests/System.IO.FileSystem.Tests/FileStream/ctor_sfh_fa_buffer_async.cs
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Expand Up @@ -29,16 +29,20 @@ public void MatchedAsync()
}

[Fact]
public void UnmatchedAsyncThrows()
public void UnmatchedAsyncIsAllowed()
{
using (FileStream fs = new FileStream(GetTestFilePath(), FileMode.Create, FileAccess.ReadWrite, FileShare.ReadWrite | FileShare.Delete, 4096, true))
{
Assert.Throws<ArgumentException>(() => CreateFileStream(fs.SafeFileHandle, FileAccess.ReadWrite, 4096, false));
// isAsync parameter is now ignored, handle.IsAsync is used instead
using (CreateFileStream(fs.SafeFileHandle, FileAccess.ReadWrite, 4096, false))
{ }
}

using (FileStream fs = new FileStream(GetTestFilePath(), FileMode.Create, FileAccess.ReadWrite, FileShare.ReadWrite | FileShare.Delete, 4096, false))
{
Assert.Throws<ArgumentException>(() => CreateFileStream(fs.SafeFileHandle, FileAccess.ReadWrite, 4096, true));
// isAsync parameter is now ignored, handle.IsAsync is used instead
using (CreateFileStream(fs.SafeFileHandle, FileAccess.ReadWrite, 4096, true))
{ }
}
}
}
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