ISOLATED STORAGE

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ISOLATED STORAGE

• SIVA PRASAD SANDIREDDY

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CONTENTS

• WHY ISOLATED STORAGE?
• INTRODUCTION
• DATA COMPARTMENT
• ISOLATED STORAGE TASKS
• STORES OF ISOLATED STORAGE
• ANTISPATING OUT OF SPACE
• CREATING FILES AND DIRECTORIES
• FINDING EXESTING FILES AND DIRECTORIES
• READ AND WRITE TO FILES
• DELETING FILES AND DIRECTORIES
• System.IO.IsolatedStorage Namespace
• REFERENCES

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WHY ISOLATED STORAGE ?

• Many programmers use the config file to keep
  the application configuration data.
• It is a read only mechanism.
• In earlier days, .ini files or registry was used
  to save application specific data.
• We can also use ordinary files but security is
  the major issue.

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INTRODUCTION

• . NET introduces a concept called Isolated
  Storage. Isolated Storage is a kind of virtual
  folder. Users never need to know where exactly
  the file is stored. All have to do is, tell the
  .NET framework to store files in Isolated
  Storage.
• using System.IO
• using System.IO.IsolatedStorage
• using System.Diagnostics

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DATA COMPARTMENT

• It is not a specific storage location it
  consists of one or more isolated storage files,
  called stores, which contain the actual 
  directory locations where data is stored.
• The data saved in the store can be any kind of
  data, from user preference information to
  application state.
• Data compartment is transparent for developer.
  Stores usually reside on the client  but a server
  application could use isolated stores.

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CONT

• Administrators can limit how much isolated
  storage an application or a user has available,
  based on an appropriate trust level.
• To create or access isolated storage, code must
  be granted the appropriate
• IsolatedStorageFilePermission.
• To access isolated storage, code must have all
  necessary native platform operating system rights
  since storage location is different depending on
  sys operating system.

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ISOLATED STORAGE TASKS

• Three main classes are necessary to perform
  tasks that involve isolated storage
• IsolatedStorageFile, which derives
  from IsolatedStorage, provides basic management
  of stored assembly and application files
• IsolatedStorageFileStream, which derives
  from System.IO.FileStream, provides access to the
  files in a store.
• IsolatedStorageScope is an enumeration that
  enables you to create and select a store with the
  appropriate isolation type.

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STORES FOR ISOLATED STORAGE

• A store exposes a virtual file system within a
  data compartment. To create and retrieve stores,
  IsolatedStorageFile provides three static method.
• Methods  GetUserStoreForAssembly or GetUserStoreFo
  rDomain  retrieve a store .
• The GetStore method can be used to specify that a
  store should roam with a roaming user profile.

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• Enumerating stores 
•  
• IsolatedStorageFile.GetEnumerator method uses to
  calculate the size of all isolated storage for
  the user.
• You can enumerate all isolated stores for the
  current user using the IsolatedStorageFile static
  method GetEnumerator. GetEnumerator takes
  an IsolatedStorageScope value and returns
  an IsolatedStorageFile enumerator. User is the
  only IsolatedStorageScope value supported.
• GetEnumerator returns an array
  ofIsolatedStorageFiles that are defined for the
  current user.

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• Deleting stores
•  
• IsolatedStorageFile.Remove method can be used in
  two different ways to delete isolated stores.
• 1) The instance method Remove does not take
  any arguments and deletes the store that calls
  it. No permissions are required for this
  operation.
• 2) The static method Remove takes
  the IsolatedStorageScope value User, and deletes
  all the stores for the user running the code.

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ANTICIPATING OUT OF SPACE

• Code that uses isolated storage is constrained by
  a quota that specifies the maximum size for the
  data compartment. This value is specified by
  Administrators.
• If the maximum allowed size is exceeded
  IsolatedStorageException is thrown and the
  operation fails.
• IsolatedStorage.CurrentSize and IsolatedStorage.Ma
  ximumSize. These two properties can be used to
  determine whether writing to the store will cause
  the maximum allowed size of the store to be
  exceeded.

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CREATING FILES AND DIRECTORIES

• To create a directory, CreateDirectory(use)
• instance method of IsolatedStorageFile.  if
  you specify a directory name that contains
  invalid characters, an IsolatedStorageException is
  generated.
• To create and open a file, use the
  IsolatedStorageFileStream constructors, passing
  in the file name, the FileMode value OpenOrCreate
  , and the store in which you want the file
  created.
• Files are case in sensitive.

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FINDING EXSTING FILES AND DIRECTORIES

• Using the GetDirectoryNames instance method
  of IsolatedStorageFile. Both single-character (?)
  and multi-character () wildcard characters are
  supported. 
• To search for a file, use the GetFileNames instanc
  e method of IsolatedStorageFile.
• For example, if there is a match on the
  directory RootDir/SubDir/SubSubDir, SubSubDir will
  be returned in the results array.

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READ AND WRITE TO FILES

• There are a number of ways to open a file within
  a store using the IsolatedStorageFileStream class.
  
• Once an IsolatedStorageFileStream has been
  obtained, it can be used to get
  a StreamReader or StreamWriter. With
  the StreamReader and StreamWriter, we can read
  and write to a file in a store as we would to any
  other file

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DELETING FILES AND DIRECTORIES

• The IsolatedStoreFile class supplies two instance
  methods for deleting directories and
  files, DeleteDirectory and DeleteFile.
•  AnIsolatedStorageFileException is thrown if you
  try to delete a file or directory that does not
  exist.
• If a wildcard character is included in the name,
  then DeleteDirectory throws an IsolatedStorageFile
  Exception while DeleteFile throws
  an ArgumentException.
• DeleteDirectory fails if the directory contains
  any files or subdirectories.

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System.IO.IsolatedStorage Namespace

• This name space contains 4 classes
• IsolatedStorage Represents the abstract base
  class from which all isolated storage
  implementations must derive.
• IsolatedStorageException The exception that is
  thrown when an operation in isolated storage
  fails.
• IsolatedStorageFile Represents an isolated
  storage area containing files and directories.
• IsolatedStorageFileStream Exposes a file within
  isolated storage.

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REFERENCES

• http//msdn.microsoft.com
• http//devcity.net/articles/42/1/isolatedstorage.a
  spx
• http//www.codeproject.com/KB/dotnet/IsolatedStora
  ge.aspx
• http//msdn.microsoft.com/en-us/library/8dzkff1s(v
  VS.80).aspx