Thank You for the answe!
You are right, but I have 2 problems with ISerializable.
1)Serializing with ISerializable is whinchester place wasteful. This is
because SerializationInfo.AddValue(string name, object value, Type type)
uses possibly different 'name's for every object. I was testing this, and
found, that when I used the same name parameter in all the instances of a
certain type, the framework intelligently noticed this, and placed the name
paramater only in one instance. But, it is not perfect, and if my object
graph has even a little complexity, it loses this intelligence.
2)The framework saves the type of all the serialized objects in the form of
a string. This string is constructed of the namespace names and the name of
the class. I can not specify an alternative name for the framework to use
for this purpose. It would be good if for example the SerializableAttribute
had such a parameter in its constructor. But it does not have. This
involves, that if I want to keep the ability to read in a document that was
serialized out with an older version of my application, I may not change the
names of my classes during the development, I may not change the names of
the namespaces, and I may not put my classes into other namspaces. I think,
these are big constraints.
----- Original Message -----
From: "Paul Stevens" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, August 11, 2004 9:55 AM
Subject: Re: serialization with varying class schema
> ---------------------- Information from the mail
header -----------------------
> Sender: "Unmoderated discussion of advanced .NET topics."
> <[EMAIL PROTECTED]>
> Poster: Paul Stevens <[EMAIL PROTECTED]>
> Subject: Re: serialization with varying class schema
> --------------------------------------------------------------------------
-----
>
> By implementing custom serialisation, you can handle any exceptions that
> occur when the class is de-serialized and the class signature has changed=
> .
> For example, in the overloaded ctor of the class used for custom
> de-serialisation the following line would check to see if a value exists =
> in
> the de-serialised stream, if it does it will assign the value to the obje=
> ct,
> if not it will create a new instance of the object.
>
> mRows =3D (info.GetValue("mRows", mRows.GetType())=3D=3Dnull?new
> RowDefinitionCollection():(Novasoft.Tomahawk.Base.RowDefinitionCollection=
> )in
> fo.GetValue("mRows", mRows.GetType()));
>
>
>
> -----Original Message-----
> From: T=F3th Zolt=E1n [mailto:[EMAIL PROTECTED]
> Sent: 05 August 2004 11:29 PM
> To: [EMAIL PROTECTED]
> Subject: [ADVANCED-DOTNET] serialization with varying class schema
>
> Hi,
>
> (Sorry for my bad English)
>
> I want to develop a windows application (an integrated development
> environment). The user should be able to edit the document (his/her
> program), save it, open it. Because of the characteristic of the document=
>
> type, I can not use XML serialization, a textual representation would be
> very inefficient. I want to use BinaryFormatter.
>
> The schema of the document will be quit complex, many classes and many
> data-fields in the classes. The difficulty is that the data-fields of any=
>
> class are not exactly known yet. I will have to add new fields to a class=
>
> (and delete existing ones) during the development. For example:
> Suppose I represent the if ... then ... else ... program structure with
>
> class If
> {
> =20 BoolExpression Condition;
> =20 Block IfTrue;
> =20 Block IfFalse;
> }
>
> the application is ready, works. I edit a 'program' with it. Then I decid=
> e
> to add a new field:
>
> class If
> {
> =20 string Comment; <<<----
> =20 BoolExpression Condition;
> =20 Block IfTrue;
> =20 Block IfFalse;
> }
>
> to make it possible for the user to attach a comment for his/her If
> structure.
> Now with the new version of my application I want to open a document that=
>
> was saved with the previous version of my application.
>
> Using the built-in .Net serialization mechanism with BinaryFormatter, the=
> =201.
> error message is about the version mismatch. I could avoid this problem w=
> ith
> specifying a concrete version writing it into the sourcecode. Now a 2.,
> bigger problem appeared: for each object Obj the .Net serializes out the
> number of member fields of Obj that have to be serialized when serializin=
> g
> Obj. Because I want to add new fields continuously, this number is varyin=
> g.
> During deserialization the .Net framework detects this variance and throw=
> s
> an exception. As the MSDN advises I tried to find a solution with the
> ISerializable interface. The problem remained, .Net still serializes the
> number of (string, value) pairs that I specify in the function
> GetObjectData.
>
> Because of this difficulty (possibly limit) I developed an own serializat=
> ion
> mechanism working similarly to .Net (through reflection). This solved my
> problem, it works (and also produces smaller files then the built-in
> mechanism :-) ).
>
> I write this letter to ask you: did I really had to develop this own
> serialization mechanism or the problem can be solved with the .Net framew=
> ork
> as well. I ask this because now I decided to review this mechanism, and m=
> ake
> it much better quality. This would take much time and I do not want to wo=
> rk
> on it needlessly.
>
> Zoli
>
>
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> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> This list is hosted by DevelopMentor=AE http://www.develop.com
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>
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>
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