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
Related
I am wondering if there is a way to get XmlSerializer in C# to change what it outputs for one property of one object. For example, if I have something like:
public class MyClass
{
public string prop1{get;}
public uint prop2{get;}
public MyClass2 class2{get;}
public MyClass3 class3{get;}
}
public class MyClass2
{
public string prop3{get;}
}
public class MyClass3
{
//Lots of properties that I want to serialize as normal
}
Now in somewhere in my code, I have something like this:
private void SerializeStuff(List<MyClass> list, string path)
{
XmlSerializer serialize = new XmlSerializer(typeof(List<MyClass>));
TextWriter writer = new StreamWriter(path);
serialize.Serialize(writer, list);
writer.Close();
}
What I want is for the serialization to work as normal, but with prop3 replaced with some other stuff. Example:
<MyClass>
<prop1>whatever</prop1>
<prop2>345</prop2>
<class2>
<somethingNotProp3>whatever</somethingNotProp3>
<somethingElseNotProp3>whatever</somethingElseNotProp3>
</class2>
<class3>
...
</class3>
</MyClass>
Is there a way to customize XmlSerializer so I don't have to write the entire Xml file manually, or is there no way to do that?
Edit:
I am pretty sure that the solution could have something to do with implementing ISerializable's GetObjectData method; however, I am not exactly sure how to implement it. I tried making MyClass2 inherit from ISerializable and implementing GetObjectData, but nothing changed. prop3 was still output in the XML file.
Use the attributes in the System.Xml.Serialization namespace to affect the way that the instance is serialized.
If you need very specialized serialization for MyClass3 that the attributes cannot handle, then implement the IXmlSerializable interface which will give you complete control over the serialization process (you can even decide on an instance-by-instance basis how to serialize the content/property).
Based on the comments, it would seem that you want to implement IXmlSerializable, as you want to change the name of the property and the value; the attributes will let you change the name of the property/element/attribute, but not allow you to perform transformations on the value (and I assume you don't want to corrupt your representation and add an extra property/value for this purpose).
Can anyone explain how to control the XML generated ?
I have a simple test class, NumberService ...
[Serializable]
public class NumberService
{
public int Number1 { get; set; }
public int Number2 { get; set; }
}
Now if I use an XmlSerializer to deserialise an instance, I get what I expected ...
<NumberService>
<Number1>23</Number1>
<Number2>45</Number2>
</NumberService>
but I was attempting to send this and Fiddler was showing ...
<NumberService>
<_x003C_Number1_x003E_k__BackingField>10</_x003C_Number1_x003E_k__BackingField>
<_x003C_Number2_x003E_k__BackingField>2</_x003C_Number2_x003E_k__BackingField>
</NumberService>
Poking around I've read that this is because of my use of automatic properties, and indeed if I changed to ...
public class NumberService
{
private int _number1;
public int Number1
{
get { return _number1; }
set { _number1 = value; }
}
public int Number2 { get; set; }
}
indeed the XML changes to ...
<NumberService>
<_number1>4</_number1>
<_x003C_Number2_x003E_k__BackingField>6</_x003C_Number2_x003E_k__BackingField>
</NumberService>
But of course I can't change _number1 to Number1 as it'd conflict with the property :-(
So how can you control the XML ?
... and a bit more reading ...
this is involving WCF data contracts
This has to do with how the DataContractSerializer handles items with the Serializable attribute applied.
When confronted with the Serializable attribute, the DataContractSerializer will defer to the semantics that you would expect when using the instance with an IFormatter implementation; in other words, it will serialize the underlying fields using the names of the fields as the keys to the data.
Because you are using auto-generated properties, what you are seeing is actually the names of the auto-generated fields that the compiler generates for you.
In order to get around this, you should apply the DataContract attribute to the class and the DataMember attribute to the properties (and you can control the name by specifying it in the attribute if you want it to differ from the property name).
You also have the option of not specifying the DataContract/DataMember attributes at all and using POCO DataContract serialization; this assumes you have a default parameterless constructor along with only serializing public properties/fields.
You should remove the [Serializable] attribute. It is not used by XML Serialization, and it is giving the wrong message to the Data Contract Serializer.
If you are using just XmlSerialization then you can use attributes from System.Xml.Serialization namespace to control Xml-Serialization for example XmlAttributeAttribute.
If you wand to use DataContractSerializer in your Wcf service, you need to mark your class with DataContract attribute and mark all properties with DataMember attribute.
IMHO DataContractSerializer is much more advanced, than old XmlSerialization
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
I have a class that is serializing very nicely - finally!
Now I want to add a property to this class, that I don't want to be serialized at all.
Is it possible to add this new property with some kind of attribute so that when I call serialize or deserialize methods, this property will go unnoticed?
[XmlIgnore]
public int DoNotSerialize { get { ... } set { ... } }
I think your looking for [XmlIgnore] attribute
I noticed the XmlSerializer is more forgiving to adding new members, removing existing ones, etc to the serialized types.
When I did this with the BinaryFormatter, and tried to deserialize the old data, it threw an exception.
What other alternatives are there for forgiving options, i.e. one that doesn't throw an exception just uses default values, skips them, etc?
Are protocol buffers forgiving in this regard?
You mention binary, and indeed BinaryFormatter is very brittle here. The problem is that BinaryFormatter is type and field based. Instead, you want a contract-based serializer, such as XmlSerialzier, DataContractSerializer (3.0), etc.
Or for binary, protobuf-net is a C# implementation of Google's "protocol buffers" wire format, but re-implemented along .NET lines; (note: I'm the author...).
It is (like the others) data-contract based, but instead of <CustomerName>asdasd</CustomerName> etc, it uses numeric tags to identify things instead; so:
[ProtoContract]
public class Customer {
[ProtoMember(1)]
public string Name {get;set;}
// ...
}
As you add more members you give them new unique numbers; this keeps it extensible without relying on any names etc. Plus it is very fast ;-p As with XmlSerializer, it will ignore things it doesn't expect (or it can store them for safe round-trip of unexpected data), and supports the same default things. You can even use your existing xml attributes:
[XmlType]
public class Customer {
[XmlElement(Order=1)]
public string Name {get;set;}
// ...
}
I could talk about this subject all day, so I'd better shut up before [too late].
You could inherit your class from ISerializable and define a custom GetObjectData. I haven't tested this, but such a class might be deserializable from a binary format, even if changes have since been made to the class.
EDIT
I just confirmed that this works. You can use code like the example below to explicitly define how an object is serialized and deserialized. It would then be up to you to make these methods work with older versions of your class. I tested this by serializing an instance of Cereal to a binary file, then making changes to the class and reading the file back in for deserialization.
[Serializable]
private class Cereal : ISerializable
{
public int Id { get; set; }
public string Name { get; set; }
public Cereal()
{
}
protected Cereal( SerializationInfo info, StreamingContext context)
{
Id = info.GetInt32 ( "Id" );
Name = info.GetString ( "Name" );
}
public void GetObjectData( SerializationInfo info, StreamingContext context )
{
info.AddValue ( "Id", Id );
info.AddValue ( "Name", Name );
}
}
I strongly recommend doing your own serialization so that you have well-defined file formats independent of the language schemes.
I actually find that the binary formatter is the most durable in the long run.
It provides excellent forward compatibility. That is to say, if you upgrade the file to a new version, it will not work with the old deserializer.
I generally create some simple data classes that I want to use for serialization. When i need to change the class, I implement the OnDeserialized / OnDeserializing methods. This allows the data to be upgraded.
The binary formatter does not require that you have a public setter for your properties, which to me is a big problem sometimes.
[Serializable]
public class data
{
private int m_MyInteger;
// New field
private double m_MyDouble;
[OnDeserializing]
internal void OnDeserializing(StreamingContext context)
{
// some good default value
m_MyDouble = 5;
}
public int MyInteger
{
get{ return m_MyInteger; }
set { m_MyInteger = value; }
}
}
I think the following post could help you. I also agree with others who said to write your own serializer. It is way better than generated code from xsd.exe .
See the post below:
Serialization and Deserialization into an XML file, C#
You can also look at the OptionalFieldAttribute for use with SerializableAttribute/NonSerializedAttribute and the BinaryFormatter and SoapFormatter
... version 1
[Serializable]
public class MyClass
{
public string field1;
[NonSerialized]
public string field2;
}
... version 2
[Serializable]
public class MyClass
{
public string field1;
[NonSerialized]
public string field2;
[OptionalField]
public string field3;
}