Bug 10545 - DataContractSerializer uses wrong order of members in class hierarchy
Summary: DataContractSerializer uses wrong order of members in class hierarchy
Status: CONFIRMED
Alias: None
Product: Class Libraries
Classification: Mono
Component: WCF assemblies (show other bugs)
Version: master
Hardware: All All
: Normal normal
Target Milestone: Untriaged
Assignee: Bugzilla
URL:
Depends on:
Blocks:
 
Reported: 2013-02-21 13:40 UTC by Daniel Hilgarth
Modified: 2017-09-06 16:45 UTC (History)
6 users (show)

See Also:
Tags:
Is this bug a regression?: ---
Last known good build:


Attachments
Sample code (1.32 KB, text/plain)
2013-02-21 13:40 UTC, Daniel Hilgarth
Details

Description Daniel Hilgarth 2013-02-21 13:40:23 UTC
Created attachment 3445 [details]
Sample code

According to the MSDN (http://msdn.microsoft.com/en-us/library/ms729813.aspx), the result of serializing an object of a class hierarchy will result in an XML with the members of each level of the hierarchy ordered alphabetically with the members of the top-most class coming first:

"- If a data contract type is a part of an inheritance hierarchy, data members of its base types are always first in the order.
- Next in order are the current type’s data members that do not have the Order property of the DataMemberAttribute attribute set, in alphabetical order.
[...]" 

Mono doesn't take this into account. Instead, Mono orders all members of the complete hierarchy alphabetical.

Steps to reproduce:

Code: See attached file

Compiled with: $> mcs DataContractSerializerBug.cs -r:System.Runtime.Serialization.dll

First run with .NET framework: $> DataContractSerializerBug.exe
Output:

<Test.Derived2 xmlns="http://schemas.datacontract.org/2004/07/" xmlns:i="http://www.w3.org/2001/XMLSchema-instance"><F>F</F><T>T</T><D>D</D><J>J</J><V
>V</V><A>A</A><E>E</E><G>G</G><K>K</K><U>U</U><Z>Z</Z></Test.Derived2>

As expected: First the members of Base (F, T), then the members of Derived (D, J, V) and finally the members of Derived2

Second run with mono: $> mono DataContractSerializerBug.exe
Output:

<Derived2 xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.datacontract.org/2004/07/"><A>A</A><D>D</D><E>E</E><F>F</F><G>G</G
><J>J</J><K>K</K><T>T</T><U>U</U><V>V</V><Z>Z</Z></Derived2>

Not as expected, the order is incorrect.

This is a real problem, because the ASP.NET Web API - or more likely, the deserialization of DataContractSerializer - requires the members in that specific order.
If that order is not correct, it will silently ignores parts of the posted request and set the corresponding properties to null / default, because it thinks the data was not provided.

There exists a workaround:
1. Add a DataContract attribute to all classes in the hierarchy
2. Annotate all members of the class hierarchy with the DataMember attribute and set the Order property. Important: The order needs to be unique not only in the current class but in all base classes, too.
Comment 1 Daniel Hilgarth 2013-02-21 13:45:46 UTC
Please ignore the small mishap with the sample. I put everything in the class Test instead of only putting the Main in that class. Fixing this doesn't change the result, though.
Comment 2 Bryan Moulton 2013-03-18 20:46:46 UTC
Confirmed this is the case. A web service hosted on a .NET environment (WCF) will not interface properly with Mono clients for this reason (and vice-versa).
Comment 3 Rodrigo Kumpera 2013-05-27 12:18:06 UTC
Martin, could you take a look at this one?

Thanks,
Rodrigo
Comment 4 Chris Turner 2014-07-08 18:59:40 UTC
bug 21073 is related to this. I have confirmed in my own testing that if I take the string data generated from a mono datacontractserializer and reorder it according to type, then the normal windows .net datcontractserializer (the one used in webapi) will indeed deserialize correctly.

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