Tag: Isolated Storage

Isolated storage in silverlight is used to store information or object therefore we don’t need to go to database to get all the information over and over again but again to use isolated storage or not should be based on case by case. Based on the implementation of the code below, I’ve found that it can compress the isolated storage file from 0.8Mb becoming 0.1 MB which is great enough for me since the quota limit is 1 mb and we try not to exceed that limit.

I’ve got this compression method from Peter Bromberg blog.

This compression method is a wrapper to SharpZip Library for Silverlight, you can download it from here, you need this library before using the code below. You can download the code below from here.

I’ve also created a Isolated Storage File with the assembly version as the file name to make sure that we have clean isolated storage file assuming the uncompressed version of isolated storage is already in production and we need to clean it up. “AssemblyVersion” properties will return the property of the current version no of the running assembly. CheckIsolatedStorageFileVersion will make sure that we always have the clean isolated storage for the new assembly.

Sample of usage
1. How to read/deserialize object from isolated storage

 Dim objMessageCodes As MessageCodes = GetIsolatedStorage(Of MessageCodes)("MyFile.txt")

2. How to write/serialize object to isolated storage

      Dim _messageCodes As New MessageCodes(mListMessage)
      WriteIsolatedStorage(_messageCodes, "myfile.txt")

These are the definition of the above function to serialize/deserialize object from your silverlight, this function is created based on Generic so it’s flexible enough to accept anything

Imports System.Collections.Generic
Imports System.ServiceModel
Imports System.Threading
Imports System.IO
Imports System.IO.IsolatedStorage
Imports System.Xml.Serialization
Imports System.Runtime.Serialization
Imports System.Reflection

Public Class MySL
 Private mAppStorage As IsolatedStorageFile

    ''' 

    ''' This is used to write the compressed object to Isolated Storage
    ''' 
    ''' 
    ''' 
    Private Sub WriteIsolatedStorage(Of T)(ByVal obj As T, ByVal filename As String)
        Try
            Dim xmlByte As Byte() = Compression.SerializeAndCompress(obj)

            Using _stream As IsolatedStorageFileStream = mAppStorage.CreateFile(filename)
                _stream.Write(xmlByte, 0, xmlByte.Length)
            End Using
        Catch ex As Exception
            Throw ex
        End Try
    End Sub

    ''' 

    ''' this is used get the compressed object from Isolated storage
    ''' 
    ''' 
    ''' 
    ''' 
    ''' 
    Private Function GetIsolatedStorage(Of T)(ByVal fileName As String) As T
        Try
            Using _stream As IsolatedStorageFileStream = mAppStorage.OpenFile(fileName, FileMode.Open)
                Using _reader As BinaryReader = New BinaryReader(_stream)
                    Dim tmpBytes As Byte()
                    ReDim tmpBytes(1024)
                    Dim fullBytes As Byte() = Nothing
                    Dim xmlStream As MemoryStream = New MemoryStream()

                    While True
                        Dim read As Integer = _reader.Read(tmpBytes, 0, tmpBytes.Length)

                        If (read <= 0) Then
                            fullBytes = xmlStream.ToArray()
                            Exit While
                        End If

                        xmlStream.Write(tmpBytes, 0, read)
                    End While

                    Dim xmlTempbyte As Byte() = xmlStream.ToArray()
                     Return Compression.DecompressAndDeserialize(Of T)(xmlTempbyte)
                End Using

            End Using

            Return Nothing

        Catch ex As Exception
            Throw ex
        End Try

    End Function

Private _compression As Compression = Nothing

    Private ReadOnly Property Compression() As Compression
        Get
            If (_compression Is Nothing) Then
                _compression = New Compression()
            End If

            Return _compression
        End Get
    End Property

    ''' 

    ''' get the assembly version
    ''' 
    ''' 
    ''' 
    ''' 
    Private ReadOnly Property AssemblyVersion() As String
        Get
            Dim name As String = Assembly.GetExecutingAssembly().FullName
            Dim asmName As AssemblyName = New AssemblyName(name)
            Return asmName.Version.ToString().Replace(".", "")
        End Get
    End Property

''' 

    ''' try to clear isolated storage
    ''' 
    ''' 
    Private Sub CheckIsolatedStorageFileVersion()
        Try
            Dim isoStorage As IsolatedStorageFile = IsolatedStorageFile.GetUserStoreForSite

            If Not mAppStorage.FileExists(AssemblyVersion + ".txt") Then
                'clear all the isolated storage
                isoStorage.Remove()
                mAppStorage.Remove()

                mAppStorage = IsolatedStorageFile.GetUserStoreForApplication()

                Using _stream As IsolatedStorageFileStream = mAppStorage.CreateFile(AssemblyVersion + ".txt")
                    Using sw As StreamWriter = New StreamWriter(_stream)
                        sw.Write(AssemblyVersion)
                    End Using
                End Using
                'Throw New Exception("Clearing!!!")
            End If

        Catch ex As Exception
            Throw ex
        End Try
    End Sub

End Class

Wrapper Class to SL SharpZipLib

Imports System
Imports System.Text
Imports System.IO
Imports System.Collections
Imports System.Diagnostics
Imports System.Collections.Generic
Imports System.Runtime.Serialization
Imports ICSharpCode.SharpZipLib.Zip.Compression
Imports System.Xml.Serialization
Imports System.Text.RegularExpressions

Public Class Compression

    Public Sub New()
    End Sub

    Public Function Serialize(Of T)(ByVal inst As T) As Byte()
        Dim dcs As New DataContractSerializer(GetType(T))

        Using ms As New MemoryStream
            dcs.WriteObject(ms, inst)
            Return ms.ToArray()
        End Using

    End Function

    Public Function Deserialize(Of T)(ByVal objectData As Byte()) As T
        Dim dcs As New DataContractSerializer(GetType(T))

        Using ms As New MemoryStream(objectData)
            Return CType(dcs.ReadObject(ms), T)
        End Using

    End Function

    Public Function SerializeAndCompress(Of T)(ByVal inst As T) As Byte()
        Dim b As Byte() = Serialize(Of T)(inst)
        Return Compress(b)
    End Function

    Public Function DecompressAndDeserialize(Of T)(ByVal bytData As Byte()) As T
        Dim bytes As Byte() = Decompress(bytData)
        Return Deserialize(Of T)(bytes)
    End Function

    Public Function Compress(ByVal strInput As String) As Byte()
        Try
            Dim bytData As Byte() = System.Text.Encoding.UTF8.GetBytes(strInput)
            Dim ms As New MemoryStream()
            Dim defl As New Deflater(9, False)

            Using s As Stream = New Streams.DeflaterOutputStream(ms, defl)
                s.Write(bytData, 0, bytData.Length)
                s.Close()
            End Using

            Return DirectCast(ms.ToArray(), Byte())
        Catch
            Throw

        End Try
    End Function

    Public Function Compress(ByVal bytData As Byte()) As Byte()
        Try

            Dim ms As New MemoryStream()
            Dim defl As New Deflater(9, False)

            Using s As Stream = New Streams.DeflaterOutputStream(ms, defl)
                s.Write(bytData, 0, bytData.Length)
                s.Close()
            End Using

            Return DirectCast(ms.ToArray(), Byte())
        Catch
            Throw

        End Try
    End Function

    Public Function Compress(ByVal bytData As Byte(), ByVal ParamArray ratio As Integer()) As Byte()

        Dim compRatio As Integer = 9
        Try
            If ratio(0) > 0 Then
                compRatio = ratio(0)
            End If
        Catch

        End Try

        Try
            Dim ms As New MemoryStream()
            Dim defl As New Deflater(compRatio, False)

            Using s As Stream = New Streams.DeflaterOutputStream(ms, defl)
                s.Write(bytData, 0, bytData.Length)
                s.Close()
            End Using

            Return DirectCast(ms.ToArray(), Byte())
        Catch
            Throw
        End Try
    End Function

    Public Function Decompress(ByVal bytInput As Byte()) As Byte()
        Try

            Dim ms As New MemoryStream(bytInput, 0, bytInput.Length)
            Dim bytResult As Byte() = Nothing
            Dim strResult As String = [String].Empty
            Dim writeData As Byte() = New Byte(4095) {}

            Using s2 As Stream = New Streams.InflaterInputStream(ms)
                bytResult = ReadFullStream(s2)
                s2.Close()
            End Using

            Return bytResult
        Catch
            Throw
        End Try
    End Function

    Public Function ReadFullStream(ByVal stream As Stream) As Byte()
        Dim buffer As Byte() = New Byte(32767) {}
        Using ms As New MemoryStream()
            While True
                Dim read As Integer = stream.Read(buffer, 0, buffer.Length)
                If read <= 0 Then
                    Return ms.ToArray()
                End If
                ms.Write(buffer, 0, read)
            End While
        End Using

        Return buffer
    End Function

End Class