Copy of class instance

[Chris Pratt]

I'm sorry to ask such a fundamental question, but is it possible to create a
copy of an object in VB.Net 2005?

I have an app which, on load, creates an instance of a class, into which it
reads a load of data from XML. What I want is to be able to declare a new
instance of this class and make it a copy of the existing instance. This
way I can spawn various instances with their own updated properties

The code "Dim NewInst as MyClass = OldInst" creates a reference to the
existing instance and, therefore, changing any properties of NewInst are
reflected in OldInst.

Is there a simple way to do what I need?

Many thanks for any help.

[Chris]

Re: Copy of class instance

Chris Pratt wrote:

I'm sorry to ask such a fundamental question, but is it possible to create a
copy of an object in VB.Net 2005?
>
I have an app which, on load, creates an instance of a class, into which it
reads a load of data from XML. What I want is to be able to declare a new
instance of this class and make it a copy of the existing instance. This
way I can spawn various instances with their own updated properties
>
The code "Dim NewInst as MyClass = OldInst" creates a reference to the
existing instance and, therefore, changing any properties of NewInst are
reflected in OldInst.
>
Is there a simple way to do what I need?
>
Many thanks for any help.
>
>

I don't know of a way to automatically do this, but you really need to
make a clone method and then inside the clone method set all the
properties to what they are in the current instance.

You may be able to do this with reflection in just a couple lines of
code. This sample code will do all the public properties.

Dim NewInstance As New IPEGCompany
Dim myType As Type = GetType(IPEGCom pany)
Dim myProperties() As Reflection.Prop ertyInfo =
myType.GetPrope rties((Reflecti on.BindingFlags .Public Or
Reflection.Bind ingFlags.Instan ce))
' Loop thru the public properties
Dim PropertyItem As Reflection.Prop ertyInfo
For Each PropertyItem In myProperties
PropertyItem.Se tValue(NewInsta nce,
Reader.GetValue (Reader.GetOrdi nal(PropertyIte m.Name)), Nothing)
Next

[Jim Wooley]

Re: Copy of class instance

I'm sorry to ask such a fundamental question, but is it possible to

create a copy of an object in VB.Net 2005?
>
I have an app which, on load, creates an instance of a class, into
which it reads a load of data from XML. What I want is to be able to
declare a new instance of this class and make it a copy of the
existing instance. This way I can spawn various instances with their
own updated properties
>
The code "Dim NewInst as MyClass = OldInst" creates a reference to the
existing instance and, therefore, changing any properties of NewInst
are reflected in OldInst.
>
Is there a simple way to do what I need?
>

You need to have your object implement IClonable and use the .Clone method
to get a copy of your object. You will be responsible for doing the cloan,
either with a serialize dehydrate/hydrate mechanism or manual property setting.
Jim Wooley

http://devauthority.com/blogs/jwooley/default.aspx

[Chris Pratt]

Re: Copy of class instance

Thanks Chris, that was really helpful. It allowed me to write a generic
function which I can use for all cases, as below:
Public Sub CopyObject(ByVa l ObjectType As Type, _
ByVal ExistingInstanc e As Object, _
ByRef NewInstance As Object)

Dim Props() As Reflection.Prop ertyInfo = _
ObjectType.GetP roperties(Refle ction.BindingFl ags.Public Or _
Reflection.Bind ingFlags.Instan ce)

For Each PropItem As Reflection.Prop ertyInfo In Props

If PropItem.CanWri te Then
PropItem.SetVal ue(NewInstance, _
PropItem.GetVal ue(ExistingInst ance, Nothing), Nothing)
End If

Next

End Sub

Incidentally, what does the Reader object refer to in your example? Is this
a better way of extracting the property values than the way I have done it?

"Chris" <no@spam.comwro te in message
news:ubFB$1asGH A.4596@TK2MSFTN GP04.phx.gbl...

Chris Pratt wrote:

>I'm sorry to ask such a fundamental question, but is it possible to
>create a copy of an object in VB.Net 2005?
>>
>I have an app which, on load, creates an instance of a class, into which
>it reads a load of data from XML. What I want is to be able to declare a
>new instance of this class and make it a copy of the existing instance.
>This way I can spawn various instances with their own updated properties
>>
>The code "Dim NewInst as MyClass = OldInst" creates a reference to the
>existing instance and, therefore, changing any properties of NewInst are
>reflected in OldInst.
>>
>Is there a simple way to do what I need?
>>
>Many thanks for any help.

>
I don't know of a way to automatically do this, but you really need to
make a clone method and then inside the clone method set all the
properties to what they are in the current instance.
>
You may be able to do this with reflection in just a couple lines of code.
This sample code will do all the public properties.
>
Dim NewInstance As New IPEGCompany
Dim myType As Type = GetType(IPEGCom pany)
Dim myProperties() As Reflection.Prop ertyInfo =
myType.GetPrope rties((Reflecti on.BindingFlags .Public Or
Reflection.Bind ingFlags.Instan ce))
' Loop thru the public properties
Dim PropertyItem As Reflection.Prop ertyInfo
For Each PropertyItem In myProperties
PropertyItem.Se tValue(NewInsta nce,
Reader.GetValue (Reader.GetOrdi nal(PropertyIte m.Name)), Nothing)
Next