StreamWriter(Stream, Encoding, Int32, Boolean) does not throw for null Encoding on all runtimes

[paulomorgado]

Type of issue

Outdated article

Description

StreamWriter(Stream, Encoding, Int32, Boolean) does not throw for null Encoding on .NET 6.0, .NET 8.0 and .NET 9.0-preview.7.

It seems to only throw on .NET Framework.

Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.io.streamwriter.-ctor?view=net-9.0#system-io-streamwriter-ctor(system-io-stream-system-text-encoding-system-int32-system-boolean)

Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System.IO/StreamWriter.xml

Document Version Independent Id

ba32d206-d8f5-fd4d-939b-16d19e9b10ac

Article author

@dotnet-bot

[rzikm]

This seems to be by design of StreamWriter. The code defaults to UTF8NoBOM

https://github.com/dotnet/runtime/blob/6072e4d3a7a2a1493f514cdf4be75a3d56580e84/src/libraries/System.Private.CoreLib/src/System/IO/EncodingCache.cs#L10

https://github.com/dotnet/runtime/blob/5f067ce8b50087e032d13a1b97ae5ec39fc54739/src/libraries/System.Private.CoreLib/src/System/IO/StreamWriter.cs#L75-L131

We should update the docs to reflect this. (also, the nullability annotations in the source code are inconsistent for the Encoding parameter across ctor overloads.

[paulomorgado]

@rzikm,

This seems to be by design of StreamWriter. The code defaults to UTF8NoBOM

https://github.com/dotnet/runtime/blob/6072e4d3a7a2a1493f514cdf4be75a3d56580e84/src/libraries/System.Private.CoreLib/src/System/IO/EncodingCache.cs#L10

https://github.com/dotnet/runtime/blob/5f067ce8b50087e032d13a1b97ae5ec39fc54739/src/libraries/System.Private.CoreLib/src/System/IO/StreamWriter.cs#L75-L131

We should update the docs to reflect this. (also, the nullability annotations in the source code are inconsistent for the Encoding parameter across ctor overloads.

It's different between .NET Framework and .NET.

I don't know how we are going to document this, but it makes .NET Standard 2.0 inconsistent across runtimes.