CODEWITHSUNDEEP
c#file-io
John Gietzen
John Gietzen

Reputation: 49544

Can you keep a StreamReader from disposing the underlying stream?

Is there a way to do this:

this.logFile = File.Open("what_r_u_doing.log", FileMode.OpenOrCreate, FileAccess.ReadWrite);

using(var sr = new StreamReader(this.logFile))
{
    // Read the data in
}

// ... later on in the class ...

this.logFile = File.Open("what_r_u_doing.log", FileMode.OpenOrCreate, FileAccess.ReadWrite);

using(var sw = new StreamWriter(this.logFile))
{
    // Write additional data out...
}

Without having to open the file twice?

I can't seem to make the StreamReader not-dispose my stream. I don't want to just let it go out of scope, either. Then the garbage collector will eventually call the Dispose, killing the stream.

Upvotes: 66

Views: 40353

Answers (9)

Thomas Levesque
Thomas Levesque

Reputation: 292465

You could use the NonClosingStreamWrapper class from Jon Skeet's MiscUtil library, it serves exactly that purpose

Upvotes: 17

Jakub
Jakub

Reputation: 31

I was able to use leaveOpen parameter without specifying all the constructor params (encoding or buffer size) like this:

using var streaReader = new StreamReader(stream, leaveOpen: true);

Upvotes: 2

Nick N.
Nick N.

Reputation: 13559

I always use something like this: (it also uses the leaveOpen argument)

public static class StreamreaderExtensions
{
    public static StreamReader WrapInNonClosingStreamReader(this Stream file) => new StreamReader(file, Encoding.UTF8, true, 1024, true);
}

Usage:

using (var reader = file.WrapInNonClosingStreamReader())
{
     ....
}

Upvotes: 1

HANiS
HANiS

Reputation: 660

Use another constructor overload where you can specifu a "leaveOpen" parameter to "true"

Upvotes: 2

Simon Buchan
Simon Buchan

Reputation: 13245

.NET 4.5 will finally fix this problem with a new constructors on StreamReader and StreamWriter that take a leaveOpen parameter:

StreamReader(Stream stream, Encoding encoding, bool detectEncodingFromByteOrderMarks, int bufferSize, bool leaveOpen)

StreamWriter(Stream stream, System.Text.Encoding encoding, int bufferSize, bool leaveOpen)

Upvotes: 87

Aaron
Aaron

Reputation: 2013

You could create a new class which inherits from StreamReader and override the Close method; inside your Close method, call Dispose(false), which as Mehrdad pointed out, does not close the stream. Same applies to StreamWriter, of course.

However, it seems like a better solution would simply be to hold onto the StreamReader and StreamWriter instances as long as you may need them. If you're already planning to keep the stream open, you might as well keep a StreamReader and StreamWriter open also. If you use StreamWriter.Flush and Stream.Seek correctly, you should be able to make this work even when doing both reading and writing.

Upvotes: 3

Mike Atlas
Mike Atlas

Reputation: 8231

Close it yourself in a try/finally clause when you're done with it.

var sr = new StreamReader();
try {
    //...code that uses sr
    //....etc
}
finally
{
    sr.Close();
}

Upvotes: 0

Mehrdad Afshari
Mehrdad Afshari

Reputation: 422016

I don't want to just let it go out of scope, either. Then the garbage collector will eventually call the Dispose, killing the stream.

Garbage collector will call the Finalize method (destructor), not the Dispose method. The finalizer will call Dispose(false) which will not dispose the underlying stream. You should be OK by leaving the StreamReader go out of scope if you need to use the underlying stream directly. Just make sure you dispose the underlying stream manually when it's appropriate.

Upvotes: 53

eflorico
eflorico

Reputation: 3629

Just remove the using-Block. You don't have to Dispose() the StreamReader if you don't want to do Dispose() the stream, I think.

Upvotes: 2

Related Questions