Does disposing StreamReader or StreamWriter close the stream?（转载）

问

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I am sending a stream to methods to write on, and in those methods I am using a binary reader/wrtier. When the reader/writer gets disposed, either by using or just when it is not referenced, is the stream closed as well??
I would send a BinaryReader/Writer, but I am using a StreamReader too (maybe I should go around that. I am only using that for GetLine and ReadLine). This is quite troublesome if it closes the stream each time a writer/reader gets closed.

 

 

答

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Yes, StreamReader, StreamWriter, BinaryReader and BinaryWriter all close/dispose their underlying streams when you call Dispose on them. They don't dispose of the stream if the reader/writer is just garbage collected though - you should always dispose of the reader/writer, preferrably with a using statement. (In fact, none of these classes have finalizers, nor should they have.)
Personally I prefer to have a using statement for the stream as well. You can nest using statements without braces quite neatly:

using (Stream stream = ...)
using (StreamReader reader = new StreamReader(stream, Encoding.Whatever))
{
}

Even though the using statement for the stream is somewhat redundant (unless the StreamReader constructor throws an exception) I consider it best practice as then if you get rid of the StreamReader and just use the stream directly at a later date, you'll already have the right disposal semantics.

 

 

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