Handling Streams

Question

I came across a point The framework will dispose of the stream used in this case when the response is completed. If a using statement is used, the stream will be disposed before the response has been sent and result in an exception or corrupt response. How to use using statement carefully in case of streams in .NET Core with examples?

Answer 1

Hi,@net 6 newbie,you could check this document related:

The using statement obtains one or more resources, executes the statements that you specify, and automatically disposes of the object.

....

When the C# or Visual Basic compiler encounters the using statement, it emits intermediate language (IL) that is equivalent to the following code that explicitly contains a try/finally block.

var buffer = new char[50];
        using StreamReader streamReader = new("file1.txt");

        int charsRead = 0;
        while (streamReader.Peek() != -1)
        {
            charsRead = streamReader.Read(buffer, 0, buffer.Length);
            //
            // Process characters read.
            //
        }

is equal to:

var buffer = new char[50];
        StreamReader? streamReader = null;
        try
        {
            streamReader = new StreamReader("file1.txt");
            int charsRead = 0;
            while (streamReader.Peek() != -1)
            {
                charsRead = streamReader.Read(buffer, 0, buffer.Length);
                //
                // Process characters read.
                //
            }
        }
        finally
        {
            // If non-null, call the object's Dispose method.
            streamReader?.Dispose();
        }

Since you 've mentioned

The framework will dispose of the stream used in this case when the response is completed

You don't have to use using statement in your scenarior for the framework would dispose it automaticlly ,just remove it.

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Answer 2

if your function returns a stream, then the caller is responsible for the Dispose(); The FileStreamResult will do the dispose when its ExecuteResultAsync() method is called.

note: if your action creates the stream, then throws an error rather than returning a FileStreamResult, then the action responsible for the dispose().