FileStream.Flush Method (Boolean)
Clears buffers for this stream and causes any buffered data to be written to the file, and also clears all intermediate file buffers.
Assembly: mscorlib (in mscorlib.dll)
Use this overload when you want to ensure that all buffered data in intermediate file buffers is written to disk.
When you call the Flush method, the operating system I/O buffer is also flushed.