Type Reason NotSupportedException The stream does not support both writing and seeking, such as if the stream is constructed from a pipe or console output. ObjectDisposedException The stream is closed. System.IO.IOException An I/O error occurred.
If the specified value is less than the current length of the stream, the stream is truncated. If the specified value is larger than the current length of the stream, the stream is expanded. If the stream is expanded, the contents of the stream between the old and the new length are not defined.
A stream must support both writing and seeking for SetLength to work.