Develop Reference

Serialize an object to XML without using attributes

Is it possible to control XmlSerializer/DataContractSerializer behavior without specifying any serialization attributes?
To be more specific, I want to control the serialization (XmlIgnore, custom attribute name etc.), but without decorating my properties.
Use cases:
A large existing class, which I don't wish to pollute with serialization attributes
Serializing a class for which no source code is available
Switching from using XmlSerializer to DataContractSerializer to JSON without changing class code
For example, how would I serialize the following without uncommenting the attributes:
// [Serializable]
public MyClass
{
// [XmlIgnore] - The following property should not be serialized, without uncommenting this line
public int DontSerializeMeEvenThoughImPublic { get; set; }
// [XmlAttribute("another_name")] - should be serialized as 'another_name', not 'SerializeMeAsXmlAttribute'
public double SerializeMeAsXmlAttribute { get; set; }
// [DataMember] - should be included
private string IWantToBeSerializedButDontDecorateMeWithDataMember { get; set; }
}

You can't (do it elegantly).
The only way to modify the way the XmlSerializer serializes classes is by using attributes (by the way SerializableAttribute is not required). The DataContractSerializer is even worse.
One possible solution is to create intermediate classes for XML serialization/desrialization and use Automapper to copy the data between the "real" class and mediator.
I've used this approach to keep the front end XML serialization concerns outside of my business logic data types.

I know this is an old question, but for the XmlSerializer part, it's interesting that no one has suggested the use of Attribute overrides.
Although not solving the Private property, but AFAIK you can't do that with attributes either, so the only route there would be the IXmlSerializable interface.
But what you can do by adding Attributes should be possible with overrides as well.
The following should work for the change wishes reflected by the outcommented XmlAttributes:
public class Program
{
public static void Main()
{
XmlAttributeOverrides overrides = new XmlAttributeOverrides();
overrides.Add(typeof(MyClass), "DontSerializeMeEvenThoughImPublic", new XmlAttributes { XmlIgnore = true });
overrides.Add(typeof(MyClass), "SerializeMeAsXmlAttribute", new XmlAttributes { XmlAttribute = new XmlAttributeAttribute("another_name") });
XmlSerializer serializer = new XmlSerializer(typeof(MyClass), overrides);
using (var writer = new StringWriter())
{
serializer.Serialize(writer, new MyClass());
Console.WriteLine(writer.ToString());
}
}
}

Serialization via XmlSerializer should work without the attributes.

how to serialize some attribute in some condition

When using XML serialization to serialize a class, how to make some attribute be outputted conditionally. i.e. In some case, it output this attribute, in other cases, it does not.

You can create an additional property which is called MyPropertySpecified, which returns a boolean.
When this property returns true, the MyProperty property will be serialized. When it returns false, it will not be serialized.
Also, you'd want to decorate that property with the XmlIgnoreAttribute, so that this specific property is not serialized.
Example:
public class Person
{
public string Name
{
get;
set;
}
[XmlIgnore]
public bool NameSpecified
{
get { return Name != "secret"; }
}
}

While works and is a rather short solution, the propertyNameSpecified pattern has some drawbacks in my opinion (pollutes the interface of your class; relies on property names; introduces implicit behavior).
If you only need to implement a simple condition (e.g. don't serialize a default value), then the DefaultValue attribute is a better choice.
For example:
public class PurchaseOrder
{
[DefaultValue("2002")]
public string Year;
}
If Year has the value "2002", it will be omitted from the XML output.

You can use OnSerializingAttribute while serializing which allows us to invoke method before serialization. You can get more information about it here

Imho you would need to implement IXmlSerializable on the class and implement the WriteXml and ReadXml methods in such a way that they only write the attribute based upon the conditions you specify and can handle reading with or without that particular attribute present upon deserialization.
IXmlSerializable at Msdn

How to serialize a class with a complex property using XML serialization in .NET?

I want to serialize a class. In this class there's a property of type Class1 that in turn has its own properties.
public abstract class ComponentBase
{
[ToSerialize] //An attribute defined my me, indicating whether or not to serialize this property.
public ComponentArgs Parameters { get; set; }
}
public class ComponentArgs
{
public string WorkingPath { get; set; }
public IList<Language> Languages { get; set; }
public string ComponentOutputPath { get; set; }
}
The information serialized must be put into a Dictionary<string,string>, such as
ComponentSettings[str_Name] = str_Value;
The method used in reading this value is Reflection
// pinfo: Property Info got via Type.GetProperties();
componentSettings.Add(pinfo.Name, pinfo.GetValue((object)this, null).ToString());
The information after serialization is:
<Parameters>MS.STBIntl.Pippin.Framework.ComponentArgs</Parameters>
instead of the value of ComponentArgs.WorkingPath.
The solution I thought of is to append to the following line an if judgement:
componentSettings.Add(pinfo.Name, pinfo.GetValue((object)this, null).ToString());
if(pinfo is ComponentArgs)
componentSettings.Add(pinfo.Name, pinfo.GetValue(
(ComponentArgs)this, null).WorkingPath+"\n"+
LanguageList+"\n"+ //Language list is a concatinated string of all elements in the list.
(ComponentArgs)this, null).ComponentOutputPath+"\n"+
);
When deserializing, add a judgement of whether the value contains more than 2 "\n", if so, extract each value from the string.
But this way seems clumsy and much more like an workaround. I wonder if there's any more professional way of doing it? My reviewer is very particular and he won't accept such a solution. If you know a way, could you please share it with me? Thanks a lot.

There are lots of ways to use inbuilt serialization.
The simplest and oldest is the [Serializable] attribute that tells .NET to serialize the members.
You can also use the WCF [DataContract] attribute to serialize stuff.
There is also the IXMLSerializable interface which allows you to implement custom XML readers and writers for you classes.
The bottom line is, there is no need to roll your own - it has been done.

Programmatically set properties to exclude from serialization

Is it possible to programmatically set that you want to exclude a property from serialization?
Example:
When de-serializing, I want to load up an ID field
When serializing, I want to NOT output the ID field

I believe there are three options here:
Use XmlIgnore attribute. The downside is that you need to know in advance which properties you want the xmlserializer to ignore.
Implement the IXmlSerializable interface. This gives you complete control on the output of XML, but you need to implement the read/write methods yourself.
Implement the ICustomTypeDescriptor interface. I believe this will make your solution to work no matter what type of serialization you choose, but it is probably the lengthiest solution of all.

It depends on serialization type. Here full example for doing this with BinaryFormatter:
You may use OnDeserializedAttribute:
[Serializable]
class SerializableEntity
{
[OnDeserialized]
private void OnDeserialized()
{
id = RetrieveId();
}
private int RetrievId() {}
[NonSerialized]
private int id;
}
And there is another way to do this using IDeserializationCallback:
[Serializable]
class SerializableEntity: IDeserializationCallback
{
void IDeserializationCallback.OnDeserialization(Object sender)
{
id = RetrieveId();
}
private int RetrievId() {}
[NonSerialized]
private int id;
}
Also you may read great Jeffrey Richter's article about serialization: part 1 and part 2.

If you are serializing to XML, you can use XMLIgnore
As in:
class SomeClass
{
[XmlIgnore] int someID;
public string someString;
}

An old post, but I found ShouldSerialize pattern
http://msdn.microsoft.com/en-us/library/53b8022e%28VS.71%29.aspx That is really HELPFUL!!!

If you want to include field during serialization but ignore it during deserialization then you can use OnDeserializedAttribute to run a method which will set default value for ID field.

If you're using XML serialization, use the [XmlIgnore] attribute. Otherwise, how to ignore a particular property is defined by the serializer itself.

The NonSerializedAttribute attribute.
http://msdn.microsoft.com/en-us/library/system.nonserializedattribute.aspx

C# automatic property deserialization of JSON

I need to deserialize some JavaScript object represented in JSON to an appropriate C# class. Given the nice features of automatic properties, I would prefer having them in these classes as opposed to just having fields. Unfortunately, the .NET serialization engine (at least, by default) totally ignores automatic properties on deserialization and only cares about the backing field, which is obviously not present in the JavaScript object.
Given that there's no standard way to name backing fields and to be honest I don't even want to bother with the "let's create a JavaScript object that looks like it had C# backing fields" approach as it sounds a bit dirty, the only way I could serialize JavaScript fields to C# auto-properties if I could force the serialization engine to somehow ignore the backing field and use the property directly. Unfortunately, I can't figure out how this is done or if this can be done at all. Any ideas would be appreciated.
EDIT: Here's an example:
Javascript:
function Cat()
{
this.Name = "Whiskers";
this.Breed = "Tabby";
}
var cat = new Cat();
This is then serialized to "{Name: 'Whiskers'}".
The C# class:
[Serializable()]
public class Cat
{
public string Name { get; set; }
public string Breed { get; set; }
}
And the deserialization code, that fails:
new DataContractJsonSerializer(typeof(Cat)).ReadObject(inputStream);
And it is apparent from the exception that it fails because it is looking for the backing field.
EDIT2: Here's the exception, if that helps (no inner exceptions):
System.Runtime.Serialization.SerializationException
"The data contract type 'Test.Cat'
cannot be deserialized because the
required data members
'<Name>k__BackingField, <Breed>k__BackingField' were not
found."

What's happening here is the deserializer is trying to guess the name of your backing fields.
You can solve this by adding explicit mappings (DataContract/DataMember attributes) like this:
[DataContract]
public class Cat
{
[DataMember]
public string Name { get; set; }
[DataMember]
public string Breed { get; set; }
}

You can do this with JavaScriptSerializer found in the System.Web.Script.Serialization namespace:
JavaScriptSerializer serializer = new JavaScriptSerializer();
Cat c = serializer.Deserialize<Cat>(jsonString);
I have POCO objects with automatic properties and this works just fine.
EDIT: I wrote about JSON Serializers in .NET which compares this serializer with DataContractJsonSerializer.

baretta's answer solved the k__BackingField bloat for me. Just a tiny addendum that you can decorate this class to auto serialize into either XML or JSON in a similar way:
[Serializable, XmlRoot, DataContract]
public class Cat
{
[XmlElement]
[DataMember]
public string Name { get; set; }
[XmlElement]
[DataMember]
public string Breed { get; set; }
}
... and then use a DataContractJsonSerializer or XmlSerializer to prepare it for your endpoint.

I'm assuming you are passing data via a web service. If you are using the WebService class with the ScriptMethod attribute uncommented-out, the web service methods can read JSON natively. They even use the same JavaScriptSerializer that was mentioned above. If you are using WCF I'm a little more fuzzy on the logic.
But make sure your JSON object are returning data for EVERY property in your class. In your error, there is mention of a Breed property that is not in your example.
Also, on the JavaScript side, do to the dynamic nature of JavaScript it is easy to add new properties to your objects. This can sometimes lead to circular references. You should remove any extra data that you might have added (just as you are sending data via the web method, then add it again once you are done).