I'm currently using XmlSerializer to, surprisingly enough :), handle de/serialization of my data structures - I find it wonderfully simple to use, but at the cost of flexibility. At the moment, I'm using it for a tree-based structure; since XmlSerializer doesn't handle cyclic structures, I've added [XmlIgnore] to my Parent property, and do a post-deserialization iteration over the tree to fix up node parents.
Is there a better way to handle this using XmlSerializer, or would it be better to rewrite the code using XmlReader/XmlWriter? I suppose implementing IXmlSerializable would work, but it seems like a fair amount of work, while still retaining the cons of XmlSerializer.
The current post-deserialization step is OK, but I'm adding a data structure that has to be serialized to a separate XML file: basically a flat list of items that need a Parent property referencing a node from the previous tree structure. This would require yet a post-deserialization step, as well as keeping both a Parent attribute as well as as ParentId (or some trickery) in the new data structure.
So, any smart (and non-fragile) ideas? Or XmlReader/XmlWriter it is?
Solution
DataContractSerializer turned out to be a pretty decent solution, with pretty much the same simplicity as XmlSerializer. I opted not to use the automatic cycle handling but instead defining and OnDeserialized decorated method to handle setting the parent node; that way, the generated XML is standard-conforming.
One thing that confused me for a while was that I got crashes on some properties after deserializing, with the backing members set to null - couldn't figure out how this was possible since the backing members were definitely initialized in all possible constructors. Debugging showed constructors were never called, and after some googling I found this SO post with an explanation.
You could try binary serialization (BinarySerializer or DataContractSerializer), which I think handles cyclic graphs somewhat better, at the cost of not having a human-readable representation of the data. Alternatively, you can try the SoapFormatter as detailed here.
Use DataContractSerializer. Mark your classes with [DataContract(IsReference = true)].
Related
I'm attempting to write a generic serializer using protobuf.net v2. However I'm running into some issues which make me wonder if perhaps what I'm doing is impossible. The objects to be serialized are of an indeterminate type to which I don't have access so I'm attempting to walk the object and add its properties to the type model.
var model = TypeModel.Create();
List<string> propertiesToSerialize = new List<string>();
foreach (var property in typeToSerialize.GetProperties())
{
propertiesToSerialize.Add(property.Name);
}
model.AutoAddMissingTypes = true;
model.Add(typeToSerialize, true).Add(propertiesToSerialize.ToArray());
For simple objects which contain only primitives this seems to work just fine. However when working with an object which contains, say, a Dictionary<string,object> I encounter an error telling me that no serializer is registered for Object.
I did look at serializing a Dictionary<string,object> in ProtoBuf-net fails but it seems the suggested solution requires some knowledge and access to the object being serialized.
Any suggestions on how I might proceed?
protobuf-net does not set out to be able to serialize every scenario (especially those dominated by object), in exactly the same way that XmlSerializer and DataContractSerializer have scenarios which they can't model. In particular, the total lack of metadata in the protobuf format (part of why it is very efficient) means that it is only intended to be consumed by code that knows the structure of the data in advance - which is not possible if too much is object.
That said, there is some support via DynamicType=true, but that would not currently be enabled for the dictionary scenario you mention.
In most cases, though, it isn't really the case that the data can be anything; more typically there are a finite number of expected data types. When that is the case, the object problem can be addressed in a cleaner way using a slightly different model (specifically, a non-generic base-type, a generic sub-type, and a few "include" options). As with most serialization, there are scenarios were it may be desirable to have a separate "DTO" model, that looks closer to the serialization output than to your domain model.
A final note: the GetProperties()/Add() approach is not robust, as GetProperties() does not guarantee any particular order to the members; with protobuf-net in the way you show, order is important, as this helps determine the keys to use. Even if the order was fixed (sorting alphabetically, for example), note that adding a member could be a breaking change.
I have a class Node something like this :
class Node {
IEnumerable<Node> inputs;
}
Which basicly defines a simple graph.
I want to serialize my graph to a human-readable form, so normally I'd say xml would be the way to go.
But XML wasn't made with cyclic dependencies in mind :)
So - what would be the best way to go for serialization of my graph ?
I can think of a few ways :
ditch XML, create my own format.
use XML, tag each node with a unique ID, store connection-lists separate from the Nodes and resolve after loading
But I think other people must have had this same problem before, so there might be some better options.
Does anyone know of a solid approach ?
For xml, I would go with the id approach (changing the DTO model such that it isn't cyclic).
Note that DataContractSerializer can support cyclic object graphs automatically by passing in true for the preserveObjectReferences option in the overloaded constructors; it won't be quite as simple as XmlSerializer output, but it will still be readable.
If you switch to WCF DataContractSerializer, you can preserve the Object References (in 3.5 SP 1 and later)
[DataContract(IsReference=true)]
Sowmy has a good write up here
I'm writing a document-based client application and I need a DOM or WPF-like, but non-visual model that:
Is a tree composed of elements
Can accept an unlimited number of custom properties that
get/set any CLR type, including collections.
Can inherit their values from their parent
Can inherit their default values from an ancestor
Can be derived/calculated from other properties, ancestors, or descendants
Support event bubbling / tunneling
There will be a core set of properties but other plugins may add their own or even create custom documents
Supports full inspection by the owning document in order to persist the tree and attributes in an XML format.
I realize that's a tall order but I was really hoping there would be something out there to help me get started. Unfortunately WPF DependencyObjects are too closed, proprietary, and coupled to WPF to be of any use as a document model. My needs also have a strong resemblance to the HTML DOM but I haven't been able to find any clean DOM implementations that could be decoupled from HTML or ported to .NET.
My current platform is .NET/C# but if anyone knows of anything that might be useful for inspiration or embedding, regardless of the platform, I'd love to know.
I don't think that it meets all of the requirements you specified, but have you considered working with an XML DOM (as opposed to an HTML DOM)? You can create an XML document programmatically in .NET and manipulate it using DOM methods and properties, and also do things like XPath queries. Check out .NET's XmlDocument object. This might be a reasonable starting point.
Maybe XMLBeans could help.
Eclipse EMF might help, but it might also be overkill for you. IMHO good designed language should make such a task extremely easy...
Netbeans platform pretty much does exactly what you want.
Are you looking for advice for an object model? How about:
// C#-ish code that probably doesn't compile
class Element {
public object GetAttribute(string attribute) {
if (this.Attributes.HasKey(attribute))
return this.Attributes[attribute];
else
return this.Parent.GetAttribute(attribute);
}
private IDictionary<string,object> Attributes;
private Element Parent;
private IList<Element> Children; // maybe not needed
// etc.
}
and go from there?
Right now, I'm currently serializing a class like this:
class Session
{
String setting1;
String setting2;
...etc... (other member variables)
List<SessionAction> actionsPerformed;
}
Where SessionAction is an interface that just has one method. All implementations of the SessionAction interface have various properties describing what that specific SessionAction does.
Currently, I serialize this to a file which can be loaded again using the default .Net binary serializer. Now, I want to serialize this to a template. This template will just be the List of SessionActions serialized to a file, but upon loading it back into memory at another time, I want some properties of these SessionActions to require input from the user (which I plan to dynamically generate GUI controls on the fly depending on the property type). Right now, I'm stuck on determining the best way to do this.
Is there some way I could flag some properties so that upon using reflection, I could determine which properties need input from user? Or what are my other options? Feel free to leave comments if anything isn't clear.
For info, I don't recommend using BinaryFormatter for anything that you are storing long-term; it is very brittle between versions. It is fine for short-lived messages where you know the same version will be used for serialization and deserialization.
I would recommend any of: XmlSerializer, DataContractSerializer (3.0), or for fast binary, protobuf-net; all of these are contract-based, so much more version tolerant.
Re the question; you could use things like Nullable<T> for value-types, and null for strings etc - and ask for input for those that are null? There are other routes involving things like the ShouldSerialize* pattern, but this might upset the serialization APIs.
If you know from start what properties will have that SessionAction, you must implement IDeserializationCallback and put to those props the attribute [NonSerialized]. When you implement the OnDeserialization method you get the new values from the user.
I am currently saving a .net ( c# ) usercontrol to the disk as a XML file by saving each property as an element in the xml document. The file is used for later recreation of the controls at runtime. I am wondering if it is possible or better to save the control as a binary file. There would be many controls so I guess it would have to have a header section describing the location and length of each saved controls. Thoughts?
Brad
BTW this is a windows app
EDIT:
what I currently have inplace is a public member function that uses the propertyDescriptior class to itinerate through all the properties and create an xml document from that.
PropertyDescriptorCollection pdc = TypeDescriptor.GetProperties(this);
for (int i = 0; i <= pdc.Count - 1; i++)
{ pdc[i].Name
pdc[i].PropertyType
pdc[i].Category
}
I will look into creating the class Serializable - thanks
We had to do this for a data-driven application where a user could create persistable views. We did an XML version to start but moved to using BinaryFormatter and the ISerializable interface as this allows us to control exactly what gets persisted and which constructors to use. For the controls we actually persisted the CodeCompileUnit that the designer has created, but that means you have to actually use a designer to lay them out.
Winforms controls don't serialize especially well, and you might have a lot of difficulty getting the base-classes (i.e. not your code) to play ball. Things like Color, for example, regularly provide surprisingly troublesome to serialize.
Xml would be an obvious (if somewhat predictable) choice, but you generally need to nominate sub-classes ahead of time. And of course, the base-classes won't be marked serializable. BinaryFormatter would avoid some of that, but as a field-based serializer, you'd have problems with the "handles" etc in the base-classes, which are meaningless serialized.
I'm not saying it can't be done - but it won't be trivial either. As a starter, you'd want to look at TypeConverter.GetProperties, and use the Converter of each to get the value as an invariant string.
just had a thought: maybe you dont need to serialize the base/sub-classes. maybe you could write another searializer that only serializes the top tier of the class inheritance hierarchy? only serializing your classes (you wrote) and maybe storing meta-data for the base classes you may derive from (so that you can re-map this on de-serialization)?? this could just be pie-in-the-sky too.