Cloning of objects in VB. NET-using memory streaming images and serialization

Cloning of objects in VB. NET

Hou Yongfeng

In 3DMAX, after creating an object (parent object), you can select Clone in the Edit menu. The following three options are available: Copy (to generate a child object of the same appearance, operations on both objects do not affect each other. Instance (parent-child interaction, parent object operations also affect child objects, and child objects) also has a Reference (not considered for the moment ).

In VB. NET, this problem also occurs. Create an instance of a complex object (which may have many different data types). After performing a series of operations, you want one or more intermediate variables (another instance) to save its status, we usually assign values to variables one by one, sometimes writing a long code :) this is actually the above Copy problem. For Instance, it is very easy to create an Instance and point it to the following:

Dim objA As New CResume 'cresume is a custom class that records resume information.

Then perform initialization, for example:

ObjA. Name = "AAA"

ObjA. Address = "Shanghai, China"

......

Dim objB As New CResume 'create an instance

ObjB = objA

In this case, objB and objA are in the same State. It is worth noting that objB changes a Name, for example:

ObjB. Name = "BBB"

In fact, the Name of objA also changes to "BBB", and the reason is very simple. They point to the same memory space.

Next we will focus on Object Clone, that is, the objects after Copy do not affect each other. The key is how to use a simple method to solve our problem, memoryStream and Binformatter can be used together to easily clone objects.

MemoryStream, as I mentioned before, is a stream that supports the storage area as memory.

Binformatter, mainly serialized and deserialized objects in binary format.

Main ideas:

First use the Serialize method of Binformatter to store the object in the MemoryStream (the operation is the same as that of other streams), and then Deserialize deserialization to get a streaming data, convert to the type of the original object. Is it easy? Haha. Let's take a look at the Code:

Code of the CResume class:

Imports System. IO

Imports System. Runtime. Serialization. formatters

Public Class CResume

'Note that the Serializable () attribute is added before the class; otherwise, serialization cannot be performed.

Dim m_Name As String 'name

Dim m_Address As String 'address

Public Property Address () As String

Get

Return m_Address

End Get

Set (ByVal NewAddress As String)

M_Address = NewAddress

End Set

End Property

Public Property Name () As String

Get

Return m_Name

End Get

Set (ByVal NewName As String)

M_Name = NewName

End Set

End Property

Public Function Clone () As CResume

Dim BF As New Binary. Binaryformatter ()

Dim MS As New MemoryStream ()

BF. Serialize (MS, Me)

MS. Position = 0

Return (CType (BF. Deserialize (MS), CResume ))

End Function

End Class

In form, you can call

Dim Resume1 As New CResume ()

Dim Resume2 As New CResume ()

Resume1.Name = "AAA"

Resume1.Address = "Shanghai, China"

Resume2 = Resume1.Clone ()

Resume1.Name = "BBB"

Resume1.Address = "Beijing, China"

Debug. WriteLine (Resume1.Name) 'is still AAA

Debug. WriteLine (Resume1.Address)

Summary: It mainly calls the stream and serialization Technology of VB. NET, which saves the tedious read/write operations and simplifies the code for object cloning.