How are methods returning a Stream implemented?

Question

The .NET framework is full of examples where a method call will return a Stream that you can then read and implement as you need to. But how does this work under the covers? What backs the stream?

Say I am writing a parser that takes some inputs and parses some data into a pre-defined format. If for example I created a MemoryStream and then write my content to it using a StreamWriter and then have the method return the stream, I will run into issues because the writer will close the underlying stream when it completes and the caller won't be able to read it as expected.

How is this typically managed? Is the content for the stream stored in the object until needed (like a byte[]) and then when the method requesting the Stream is invoked it creates it at that time or what?

Answer 1

The stream can be backed by many different things. That's the whole idea of streams deriving from the Stream abstract base class.

The stream can be backed by an OS level file stream, by memory, by an HTTP connection, or anything else that can fulfill the Stream contract.

In the case of a MemoryStream the backing storage is just a block of memory.

In the case of StreamWriter, calling Dispose() on it will close the underlying stream. Make sure you don't dispose the writer as long as you still want to use the stream. Also, if you want to re-access a MemoryStream after writing to it, be sure and set the position to the beginning, e.g.:

memStream.Seek(0, SeekOrigin.Begin);

Answer 2

A stream is an abstraction of a sequence of bytes, such as a file, an input/output device, an inter-process communication pipe, or a TCP/IP socket. The Stream class and its derived classes provide a generic view of these different types of input and output, isolating the programmer from the specific details of the operating system and the underlying devices. [MSDN said]

so i suppose you using serialize , for Serialization using different formats in .NET by using stream need to define your demands

Serialization is the process of converting an object in to bytes for persistence storage. The deserialization process converts the bytes to object without any loss of data. Serialization is used for storing values in files or database, send an object through the network and to convert back to the original object format. The .NET Framework provide a set of Framework Class Libraries (FCL) for making the serialization process easy. It is very useful for sending data between two different applications.

The .NET Framework supports binary serialization and XML serialization formats. XML serialization serializes only public fields. But, binary serialization will serialize all private and public fields. Serialization can be performed either as basic or custom. Basic serialization happens when a class has the SerializableAttribute attribute applied. Basic serialization doesn't support for versioning. A custom serialization class must be marked SerializableAttribute and implement the ISerializable interface. The user can implement custom serialization for both Binary and XML serialization formats. GetObjectData needs to be overridden for a custom application. The sample application uses custom serialization for both binary and XML serialization. The .NET Framework supports designer serialization which is associated with development tools. Custom serialization

Custom serialization is the process of controlling the serialization and deserialization process. Custom serialization can be implemented by running custom methods during and after serialization or by implementing the ISerializable interface. Custom serialization is used for versioning the serialization object. If the serialized object has changed the object state (added a new file in later version), custom serialization is used for getting the values without loss of data. The versioning of the serialized object may fail due to missing attributes.

If the user wants to use custom methods during and after serialization, the user should apply the custom serialization support using OnDeserializedAttribute, OnDeserializingAttribute, OnSerializedAttribute and OnSerializingAttribute attributes for customizing the data during serialization and deserialization. The OptionalFieldAttribute attribute is used for ignoring the old version data for deserialization. The formatter doesn't give any error during deserialization. It allows for updating the object before and after serialization/deserialization.

i think below link help you
http://www.codeproject.com/Articles/422474/Serialization-using-different-formats-in-NET

Answer 3

StreamWriter has an overloaded constructor that you can use to instruct the write to not close the stream.

Also, the Stream should have a .WriteBytes method that allows you to avoid a StreamWriter altogether.