Why a BinaryWriter closes the outer Stream on disposal, and how to prevent that? (.NET C#)

Question

I have one method that receives a Stream to write on it using a BinaryWriter. But when I dispose this BinaryWriter it also closes the stream. Can I leave it undisposed so I can leave my stream open?

Answer 1

Just do not call Dispose, use Flush instead, its safe.

Answer 2

As of .NET 4.5, the BinaryWriter class has a new constructor that takes a boolean parameter to indicate whether to leave the stream open or not.

Ref: http://msdn.microsoft.com/en-us/library/gg712841.aspx

public BinaryWriter(
    Stream output,
    Encoding encoding,
    bool leaveOpen
)

Answer 3

In the case of BinaryWriter, that isn't a direct option (although some stream wrappers do allow you to control this, for example GZipStream etc).

Jon has a NonClosingStreamWrapper in MiscUtil which should work: you wrap your stream in the non-closing wrapper, and give the wrapper to BinaryWriter. This essentially passes through everything except Close() and Dispose().

Answer 4

The protected BinaryWriter.Dispose(bool) method is virtual, and all it does is closes the stream (you can check that it is true in Reflector). -This method is called by the Dispose() method.

You can simply inherit a class from the BinaryWriter and override the Dispose(bool) method to do nothing, or something else alltogether.