首先要说明的是，该方法仅对将session存放于sql server中有效。很多人说session存放于sql server中效率太低，我觉得这只能说低一些，不能说太低。这其中的好处更大一些，如果将session存放在进程内，应用程序一重启就没了，有时候很麻烦；存放在进程外和存放在数据库中效率几乎一样。

这个类是从.net framework的源码里得到的，删除了updatesession的部分，只保留了获得session的部分，可以单独作为一个类或者放在类中做私有类使用。

#Region "分析Session的私有类"
    Private Class altSerialization
        ' Methods
        Shared Sub New()
            Dim typeArray1 As Type() = New Type(21) {}
            typeArray1(1) = GetType(String)
            typeArray1(2) = GetType(Integer)
            typeArray1(3) = GetType(Boolean)
            typeArray1(4) = GetType(DateTime)
            typeArray1(5) = GetType(Decimal)
            typeArray1(6) = GetType(Byte)
            typeArray1(7) = GetType(Char)
            typeArray1(8) = GetType(Single)
            typeArray1(9) = GetType(Double)
            typeArray1(10) = GetType(SByte)
            typeArray1(11) = GetType(Short)
            typeArray1(12) = GetType(Long)
            typeArray1(13) = GetType(UInt16)
            typeArray1(14) = GetType(UInt32)
            typeArray1(15) = GetType(UInt64)
            typeArray1(16) = GetType(TimeSpan)
            typeArray1(17) = GetType(Guid)
            typeArray1(18) = GetType(IntPtr)
            typeArray1(19) = GetType(UIntPtr)
            altSerialization.s_serializedTypes = typeArray1
        End Sub

        Private Sub New()
        End Sub

        Public Shared Function ReadValueFromStream(ByVal reader As BinaryReader) As Object
            Dim numArray1 As Integer()
            Dim num1 As Integer
            Dim buffer1 As Byte()
            Dim formatter1 As System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
            Dim obj1 As Object = Nothing
            Select Case CType(reader.ReadByte, TypeID)
                Case CType(CType(CType(1, TypeID), TypeID), TypeID)
                    Return reader.ReadString
                Case CType(CType(CType(2, TypeID), TypeID), TypeID)
                    Return reader.ReadInt32
                Case CType(CType(CType(3, TypeID), TypeID), TypeID)
                    Return reader.ReadBoolean
                Case CType(CType(CType(4, TypeID), TypeID), TypeID)
                    Return New DateTime(reader.ReadInt64)
                Case CType(CType(CType(5, TypeID), TypeID), TypeID)
                    numArray1 = New Integer(4) {}
                    num1 = 0
                    GoTo Label_00CA
                Case CType(CType(CType(6, TypeID), TypeID), TypeID)
                    Return reader.ReadByte
                Case CType(CType(CType(7, TypeID), TypeID), TypeID)
                    Return reader.ReadChar
                Case CType(CType(CType(8, TypeID), TypeID), TypeID)
                    Return reader.ReadSingle
                Case CType(CType(CType(9, TypeID), TypeID), TypeID)
                    Return reader.ReadDouble
                Case CType(CType(CType(10, TypeID), TypeID), TypeID)
                    Return reader.ReadSByte
                Case CType(CType(CType(11, TypeID), TypeID), TypeID)
                    Return reader.ReadInt16
                Case CType(CType(CType(12, TypeID), TypeID), TypeID)
                    Return reader.ReadInt64
                Case CType(CType(CType(13, TypeID), TypeID), TypeID)
                    Return reader.ReadUInt16
                Case CType(CType(CType(14, TypeID), TypeID), TypeID)
                    Return reader.ReadUInt32
                Case CType(CType(CType(15, TypeID), TypeID), TypeID)
                    Return reader.ReadUInt64
                Case CType(CType(CType(16, TypeID), TypeID), TypeID)
                    Return New TimeSpan(reader.ReadInt64)
                Case CType(CType(CType(17, TypeID), TypeID), TypeID)
                    buffer1 = reader.ReadBytes(16)
                    Return New Guid(buffer1)
                Case CType(CType(CType(18, TypeID), TypeID), TypeID)
                    If (IntPtr.Size = 4) Then
                        Return New IntPtr(reader.ReadInt32)
                    End If
                    GoTo Label_01D3
                Case CType(CType(CType(19, TypeID), TypeID), TypeID)
                    If (UIntPtr.Size = 4) Then
                        Return New UIntPtr(reader.ReadUInt32)
                    End If
                    GoTo Label_0201
                Case CType(CType(CType(20, TypeID), TypeID), TypeID)
                    formatter1 = New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
                    Return formatter1.Deserialize(reader.BaseStream)
                Case CType(CType(CType(21, TypeID), TypeID), TypeID)
                    GoTo Label_022B
            End Select
            Return obj1
Label_00BD:
            numArray1(num1) = reader.ReadInt32
            num1 = (num1 + 1)
Label_00CA:
            If (num1 < 4) Then
                GoTo Label_00BD
            End If
            Return New Decimal(numArray1)
Label_01D3:
            Return New IntPtr(reader.ReadInt64)
Label_0201:
            Return New UIntPtr(reader.ReadUInt64)
Label_022B:
            Return Nothing
        End Function

        ' Fields
        Private Shared s_serializedTypes As Type()

        ' Nested Types
        Private Enum TypeID
            ' Fields
            [Boolean] = 3
            [Byte] = 6
            [Char] = 7
            DateTime = 4
            [Decimal] = 5
            [Double] = 9
            Guid = 17
            Int16 = 11
            Int32 = 2
            Int64 = 12
            IntPtr = 18
            [Null] = 21
            [Object] = 20
            SByte = 10
            [Single] = 8
            [String] = 1
            TimeSpan = 16
            UInt16 = 13
            UInt32 = 14
            UInt64 = 15
            UIntPtr = 19
        End Enum
    End Class
#End Region