.NET 4.5

gistfile1.cs

[SecuritySafeCritical]
public virtual void Flush(bool flushToDisk)
{
  if (this._handle.IsClosed)
	{
		__Error.FileNotOpen();
	}
	this.FlushInternalBuffer();
	if (flushToDisk && this.CanWrite)
	{
		this.FlushOSBuffer();
	}
}

private void FlushInternalBuffer()
{
  if (this._writePos > 0)
	{
		this.FlushWrite(false);
		return;
	}
	if (this._readPos < this._readLen && this.CanSeek)
	{
		this.FlushRead();
	}
}

[SecuritySafeCritical]
private void FlushOSBuffer()
{
  if (!Win32Native.FlushFileBuffers(this._handle))
	{
		__Error.WinIOError();
	}
}