What are the differences between FileStream.Flush(), FlushAsync(), and Dispose()?

Question

ICSM Computer · Answer

Here’s a clear breakdown of the differences between FileStream.Flush(), FlushAsync(), and Dispose() in C#:

fileStream.Flush();

Use when you want to make sure data is written immediately but continue using the stream.

await fileStream.FlushAsync();

Use when you're working in an async method and want to avoid blocking.

Purpose: Flushes buffers and releases all resources, including the underlying file handle.
Automatically calls Flush(), then disposes.
Once disposed, the stream cannot be reused.

fileStream.Dispose();
// OR with using:
using (var fs = new FileStream(...))
{
    // ... use fs
} // Dispose() is called automatically here

Use when you're done with the stream.

Method	Flushes Data	Asynchronous	Closes Stream
`Flush()`	Yes	No	No
`FlushAsync()`	Yes	Yes	No
`Dispose()`	Yes	No	Yes

Use using or await using blocks to ensure Dispose() is always called, even on exceptions.
Call Flush() or FlushAsync() if you want to write changes without closing the file.

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