When overridden in a derived class, gets a value indicating whether the current stream supports reading.
true if the stream supports reading; otherwise, false.
If a class derived from System.IO.Stream does not support reading, calls to the Stream.Read(Byte[], int, int), Stream.ReadByte, and Stream.BeginRead(Byte[], int, int, AsyncCallback, object) methods throw a NotSupportedException.
If the stream is closed, this property returns false.