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Desserialize a Custom Class that had its structure changed

Posted on 2010-09-22
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Last Modified: 2012-06-27
Hi experts.

Suppose that I have a Class that defines a Product in my catalog. This class have 2 attributes: Product_Code and Product_Description, both as string.

A instance of this class was serialized as XML and saved to the disk.

Now, suppose that a new attribute, called Product_Supplier was added to the class. What will happen if I try to deserialize the XML file that was previously saved? Is there a way to perform this action sucessfully, including when attributes are deleted or have it's names changed?

Thanks a lot.
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Question by:regisdaniel
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4 Comments
 
LVL 55

Assisted Solution

by:Jaime Olivares
Jaime Olivares earned 600 total points
ID: 33740640
There is no problem is a property is missing in the xml. It will keep the default or existent value.
If the attribute name is changed then you will have a problem with deserialization.
If you want to handle this kind of situation, you can do custom serialization and ignore not-known tags.
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LVL 2

Assisted Solution

by:DmitryVasiliev
DmitryVasiliev earned 600 total points
ID: 33741358
You can use SoapAttribure and SoapElement parameters to deserialize fields with changed name

[SoapAttribute(DataType = "date", AttributeName = "CreationDate")]
[SoapElement(DataType = "nonNegativeInteger", ElementName = "PosInt")]

See details here: http://msdn.microsoft.com/en-us/library/system.xml.serialization.soapattributeattribute(v=VS.90).aspx
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LVL 16

Accepted Solution

by:
kris_per earned 800 total points
ID: 33748604

By default,
if new attribute added in class: old xml will serialize fine; new attribute field in class will be left untouched with the default value.

if an attribute is deleted in class: old xml will serialize fine; If you still want to check/process the old value, then you can use UnknownAttribute event handler of XmlSerializer (or UnknownNode event for nodes)

if attribute name changed: by default this is like an attribute with old name is deleted and a new attribute is added. But you can force attribute name in xml whatever the field name is using XmlAttribute attribute like:
[XmlAttribute(AttributeName = "CreationDate")]
public DateTime Today; // though field name is Today, attribute in xml will be CreationDate


For more details, check out this msdn link => http://msdn.microsoft.com/en-us/library/system.xml.serialization.xmlserializer.aspx
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Author Closing Comment

by:regisdaniel
ID: 33809074
Thanks a lot!!!
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