Chapter 3-Lesson 3

• Both GZip and DEFLATE compression systems allow compression for a maximum of 4GB data.
• GZipStream is useful for wider distribution scenario while DeflateStream is useful for relatively smaller size (because it does not include header information)
• Compression Streams would always wrap the FileStream with compressed data, whether during Compression or Decompression.

Chapter 2-Lesson 2

• Most operations with Streams involve the File class
• StreamReader and StreamWriter classes allow for sequential reading and writing of data.
• Static methods in the File class are almost identical to the FileInfo class.
• Simple Create( ) method (or Open, etc) would return a FileStream object where as CreateText( ) method (or OpenText, etc) would return a StreamReader/StreamWriter object.
• The Directory class provides static methods for routine directory operations.
• The FileAccess enum provides the possible rights assigned when accessing a file.
• Using FileAccess.Read would allow read-only access, whereas FileAccess.Write would allow append-only access.
• The FileMode enum determines whether file would be created or opened or deleted, etc.
• FileMode.Append can only be used with FileAccess.Write
• FileMode.Create overwrites any existing file while FileMode.CreateNew throws an exception if file exists.
• Similarly FileMode.Open would throw an exception if file does not exist but FileMode.OpenOrCreate wont.
• The Length property of the Stream class returns length of a stream in bytes.
• The SetLength property will Truncate (shrink) the contents of the stream if new length is lesser than the old one and vice versa.
• The StreamReader is intended to read the Stream as a string rather than as bytes.
• The StreamReader class is derived from the abstract TextReader class. StreamWriter derives from TextWriter abstract class.
• Similarly StringReader/StringWriter inherit from TextReader/TextWriter class. StringWriter uses a StringBuilder.
• For non-textual data there are BinaryReader/BinaryWriter classes.
• One use of MemoryStream is like we use datasets for database operations. You may continue to write on a MemoryStream and when you decide to make chages permanent you wirte a MemoryStream to a FileStream. This would lock the actual file for a short period of time reducing accessibility downtime.