Value gets or sets the value of this parameter. Null values are accepted as either null or DBNull. If the parameter's Direction is Output or ReturnValue, any null values received are DBNull values. The input type is inferred from the value itself. Binary data can be accepted as a byte[] or as an instance of a System.IO.Stream class. Binary output will be a System.IO.Stream instance. 

Value (MSDN) 

DBNull (MSDN) 

Direction