fix https://github.com/dotnet/runtime/issues/110899

[tony-hu-avepoint]

#110899
don't flush stream at read mode.

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[vcsjones]

This has been mentioned in other issues such as #80427 and #25129, but Dispose calling Flush even on a read Stream is intentional.

My comment is that CryptoStream has had this behavior for at least 12 years (I checked 2.0, I assume it had it since 1.1, making it almost 15 years), and that at least one Stream type (FileStream) has an observable effect from calling Flush. Therefore it is probable that someone has a dependency on Flush being called from CryptoStream on a custom stream type (and no one has a dependency on Flush not being called by CryptoStream).

[tony-hu-avepoint]

This has been mentioned in other issues such as #80427 and #25129, but Dispose calling Flush even on a read Stream is intentional.

My comment is that CryptoStream has had this behavior for at least 12 years (I checked 2.0, I assume it had it since 1.1, making it almost 15 years), and that at least one Stream type (FileStream) has an observable effect from calling Flush. Therefore it is probable that someone has a dependency on Flush being called from CryptoStream on a custom stream type (and no one has a dependency on Flush not being called by CryptoStream).

Appreciate the clarification