I'm trying to serialize the Outer class shown below, and create an XElement from the serialized XML. It has a property which is of type Inner. I'd like to change the name of both Inner (to Inner_X) and Outer (to Outer_X).
class Program
{
static void Main(string[] args)
{
using (MemoryStream memoryStream = new MemoryStream())
{
using (TextWriter streamWriter = new StreamWriter(memoryStream))
{
var xmlSerializer = new XmlSerializer(typeof(Outer));
xmlSerializer.Serialize(streamWriter, new Outer());
XElement result = XElement.Parse(Encoding.ASCII.GetString(memoryStream.ToArray()));
}
}
}
}
[XmlType("Outer_X")]
public class Outer
{
public Outer()
{
this.InnerItem = new Inner();
}
public Inner InnerItem { get; set; }
}
[XmlType("Inner_X")]
public class Inner
{
}
This creates an XElement which looks like this:
<Outer_X xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<InnerItem />
</Outer_X>
What I would like is:
<Outer_X xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Inner_X />
</Outer_X>
I want to keep the information about how a class should be renamed with that class. I thought I could do this with the XmlType attribute. However, this is ignored and the property name is used instead.
I've looked here and here, amongst other places, and feel like this should work. What am I missing?
Clarification
By "keep(ing) the information about how a class should be renamed with that class", what I mean is that the term Inner_X should only appear in the Inner class. It should not appear at all in the Outer class.
When XmlSerializer serializes a type, the type itself controls the names of the elements created for its properties. I.e. the property name becomes the element name, unless overridden statically by XmlElementAttribute.ElementName. XmlTypeAttribute.TypeName generally only controls the element name when an instance of the type to which it is applied is not being serialized as the property of some containing type -- for instance, when it is the root element, or when it is contained in a collection that is being serialized with an outer container element. This design avoids name collisions in cases where there are multiple properties of the same type within a given type.
However, there is an exception in the case of polymorphic property types. For these, XmlSerializer has an option to use the XML type name of each of the possible polymorphic types as the element name, thereby identifying the actual c# type from which the element was created. To enable this functionality, one must add multiple [XmlElement(typeof(TDerived))] attributes to the property, one for each possible type TDerived.
You can use this capability to generate the XML you require by introducing a psuedo-polymorphic proxy property:
[XmlType("Outer_X")]
public class Outer
{
public Outer()
{
this.InnerItem = new Inner();
}
[XmlIgnore]
public Inner InnerItem { get; set; }
[XmlElement(typeof(Inner))]
[XmlElement(typeof(object))]
[Browsable(false), EditorBrowsable(EditorBrowsableState.Never), DebuggerBrowsable(DebuggerBrowsableState.Never)]
public object InnerItemXmlProxy
{
get
{
return InnerItem;
}
set
{
InnerItem = (Inner)value;
}
}
}
Then the output is as you require:
<Outer_X xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Inner_X />
</Outer_X>
Prototype fiddle.
However, as #evk commented, if your Outer class contains multiple properties of the same type, this cannot be done.
One other option to think about: if you simply don't want to manually duplicate the "Inner_X" type name strings in multiple locations (i.e. in both the [XmlType(string name)] and [XmlElement(string name)] attributes) you could centralize the type names by making them be public const:
[XmlType(Outer.XmlTypeName)]
public class Outer
{
public const string XmlTypeName = "Outer_X";
public Outer()
{
this.InnerItem = new Inner();
}
[XmlElement(Inner.XmlTypeName)]
public Inner InnerItem { get; set; }
}
[XmlType(Inner.XmlTypeName)]
public class Inner
{
public const string XmlTypeName = "Inner_X";
}
Update
I just noticed your comment I intend Inner to be an abstract base class, each subclass of which will serialize to different element names. If this is the case, then XmlSerializer can indeed be made to use the XML type name as the element name -- but only when it can determine statically that the property type is actually polymorphic due to the presence of multiple [XmlElement(typeof(TDerived))] attributes. Thus the following classes will generate the XML you require:
[XmlType("Outer_X")]
public class Outer
{
public Outer()
{
this.InnerItem = new InnerX();
}
[XmlElement(typeof(InnerX))]
[XmlElement(typeof(Inner))] // Necessary to inform the serializer of polymorphism even though Inner is abstract.
public Inner InnerItem { get; set; }
}
public abstract class Inner
{
}
[XmlType("Inner_X")]
public class InnerX : Inner
{
}
You need to set the element name of the property, not the xml type of the inner class.
Try this:
[XmlType("Outer_X")]
public class Outer
{
public Outer()
{
this.InnerItem = new Inner();
}
[XmlElement("Inner_X")]
public Inner InnerItem { get; set; }
}
public class Inner
{
}
This is extremely simple to achieve. You need to use the XmlRootAttribute for the class and the XmlElementAttribute for the members as explained here on MSDN.
[XmlRoot(ElementName = "Outer_X")]
public class Outer
{
[XmlElement(ElementName = "Inner_X")]
public Inner InnerItem { get; set; } = new Inner();
}
public class Inner { }
I have created a working .NET Fiddle to exemplify this. This SO Q & A seemed to address this similar concern. Finally, when decoding the XML to a string you should probably use a different encoding, no? According to this, strings are UTF-16 encoded -- not a big deal, but figured I'd call attention to it.
The fiddle I shared results in the following XML:
<Outer_X xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Inner_X />
</Outer_X>
Update
After you updated your question with the clarification, I now understand what you'd asking. Unfortunately, (to my knowledge) this cannot be controlled as you desire via attributes. You'd have to either create your own XML serializer / deserializer or accept the fact that there are limitations with the attribute support.
Related
I am successfully using XML serializer to serialize a Microsoft.VisualStudio.Services.Common.SerializableDictionary<T1, T2>.
Now I want to add a guid string to SerializableDictionary and serialize it as well. I therefore created the following class:
public class SerializableDictWithGuid<T1, T2> : SerializableDictionary<T1, T2>, IMyInterface
{
[XmlElement(ElementName = idXml001)]
public string Guid { get; set; } = string.Empty;
}
When serializing SerializableDictWithGuid with the below code, the guid string is missing in the XML output.
public class XmlSerializeHelper<T> where T : class
{
public static string Serialize(T obj)
{
try
{
System.Xml.Serialization.XmlSerializer xsSubmit = new System.Xml.Serialization.XmlSerializer(typeof(T));
using (var sww = new StringWriter())
{
using (XmlTextWriter writer = new XmlTextWriter(sww) { Formatting = Formatting.Indented })
{
xsSubmit.Serialize(writer, obj);
}
return sww.ToString();
}
}
catch (Exception ex)
{
logger.log(ex);
}
return string.Empty;
}
}
Minimal reproducible example
SerializableDictWithGuid <string, string> test = new SerializableDictWithGuid <string, string>() { Guid = "123" };
XmlSerializeHelper<SerializableDictWithGuid <string, string>>.Serialize(test);
Question: how can I add properties to SerializableDictionary and include them in XML serialization?
XmlSerializer does not support dictionaries, so SerializableDictionary<T1, T2> works by implementing IXmlSerializable. I.e., it serializes itself manually using handcrafted code. As such, that code knows nothing about the properties of subclasses, and doesn't have any code to discover and serialize them automatically.
Luckily it appears that IXmlSerializable.ReadXml() and IXmlSerializable.WriteXml() were not implemented explicitly, so it should be possible to re-implement them via interface re-implementation and still call the base class methods. And, while in general it's tricky to implement IXmlSerializable, if you make your Guid be an XML attribute rather than an element, implementation becomes simple because, while the design of IXmlSerializable doesn't allow for derived classes to inject child elements, it does allow for derived classes to inject custom attributes:
public class SerializableDictWithGuid<T1, T2> : SerializableDictionary<T1, T2>, IMyInterface, IXmlSerializable // Re-implement IXmlSerializable
{
const string idXml001 = "idXml001";
public string Guid { get; set; } = string.Empty;
public new void ReadXml(XmlReader reader)
{
reader.MoveToContent();
// At this point the reader is positioned on the beginning of the container element for the dictionary, so we can get any custom attributes we wrote.
Guid = reader.GetAttribute(idXml001);
base.ReadXml(reader);
}
public new void WriteXml(XmlWriter writer)
{
// At this point the container element has been written but nothing else, so it's still possible to add some attributes.
if (Guid != null)
writer.WriteAttributeString(idXml001, Guid);
base.WriteXml(writer);
}
}
This results in XML that looks like:
<SerializableDictWithGuidOfStringString idXml001="123">
<item>
<key>
<string>hello</string>
</key>
<value>
<string>there</string>
</value>
</item>
</SerializableDictWithGuidOfStringString>
The XML Standard states that
Attributes are used to associate name-value pairs with elements.
In general attributes are appropriate for fixed sets of simple, primitive values such as names and IDs. Complex values with multiple internal properties, or values that repeat (i.e. collections) should be child elements, not attributes. Since an identifying Guid is a primitive value, using an attribute is appropriate. See:
XML attribute vs XML element
Should I use Elements or Attributes in XML?
Demo fiddle here.
I was wondering if I have an object that contains a field which has its deserialization process dependant on another field, how can I deserialize the parent object?
Container
class Container
{
public int Id { get; set; }
public object Data { get; set; } //deserialization depends on first field
}
Hierarchy
class FieldType1
{
public string Value { get; set; }
}
class FieldType2
{
public int Numbers { get; set; }
}
Given the example above if I have a Dictionary<int,Type> how can I deserialize an object that comes as a string like the one below?:
var container = new Container { Data = new FieldType1 { Value = "sata" }};
var str = JsonConvert.SerializeObject(container);
var clone = JsonConvert.DeserializeObject<Container>(str);//has dependant field on another field
As you can see in my example above I always have the same container type.but one property differs.
Update
After some answers here could it be possible to keep only one type of parent object and instead have a base type for the second field ?
[JsonSubTypes.KnownSubType(typeof(Child1),1)]
[JsonSubTypes.KnownSubType(typeof(Child2),2)]
public abstract Child
{
}
public class Parent{
public int Id;
public Child child;
}
Can i decorate somehow the parent to know how to deserialize its second field (similar to JsonSubTypes)?
Summing it up i do not want to have P,P1,P2..Pn types for parent.
I want to have one type P for parent with F1,F2...Fn types for its second field.So that when i deserialize i would just say JsonConvert.DeserializeObject<P> while the converter takes care of which concrete type is the second field:
Parent c1=new P{ id=1,child=new Child1()};
Parent c2=new P{ id=2,child=newChild2()};
List<Parent> items=new List<Parent>{c1,c2};
var str=JsonConvert.SerializeObject(items);
var clone=JsonConvert.DeserializeObject<List<Parent>>(str);
At a first glance, I'd simply use a simple function that you could put into a SomeNameParser/Converter class.
Pesudo C# code, something like the following:
var jObject = JObject.Parse(obj.Data);
switch (jObject["firstField"])
{
case "fieldType1":
return JsonConvert.DeserializeObject<string>(str);
case "fieldType2":
return JsonConvert.DeserializeObject<int>(str);
default:
Throw new Exception( make this meaningful)
}
Improvements
You could make the parsing of the firstField do a lookup to return a System.Type, then pass the type to JsonConvert.Deserialize(obj.Data, type) which would save the repetitive JsonConvert.
Hopefully you can see the general pattern.
Imagine having XML structure like the following:
[XmlRoot("Foo")]
public class Foo
{
[XmlElement("Bar")]
public Bar Bar { get; set; }
[XmlElement("SuperImportant")]
public SuperImportant SuperImportant { get; set; }
}
[XmlRoot("Bar")]
public class Bar
{
[XmlElement("Baz")]
public XmlElement Baz { get; set; }
}
[XmlRoot("SuperImportant")]
public class SuperImportant
{
[XmlElement("MegaImportant")]
public string MegaImportant { get; set; }
}
Baz defined as XmlElement for some reason.
Now check this code:
var template = #"
<Foo>
<Bar>
{0}
</Bar>
<SuperImportant>
<MegaImportant>42</MegaImportant>
</SuperImportant>
</Foo>";
var selfClosed = new StringReader(String.Format(template, "<Baz/>"));
var openClosePair = new StringReader(String.Format(template, "<Baz></Baz>"));
XmlSerializer xmlSerializer = new XmlSerializer(typeof(Foo));
var o1 = (Foo)xmlSerializer.Deserialize(selfClosed);
Console.WriteLine(o1.SuperImportant == null); // True, it's not there
var o2 = (Foo)xmlSerializer.Deserialize(openClosePair);
Console.WriteLine(o2.SuperImportant == null); // False, it's there
As you can see, if some tag, defined as XmlElement in class definition appears to be self closed, the element right after its parent tag is nulled. How can I configure XmlSerializer to treat self-closed tags as open-close pairs? SuperImportant should be deserialized in both cases, but it's not in the former, which is wrong.
You should mark the property Baz with [XmlAnyElement("Baz")] like so:
[XmlRoot("Bar")]
public class Bar
{
[XmlAnyElement("Baz")]
public XmlElement Baz { get; set; }
}
As explained in the docs, this attribute
Specifies that the member (a field that returns an array of XmlElement or XmlNode objects) contains objects that represent any XML element that has no corresponding member in the object being serialized or deserialized.
...
You can also apply the XmlAnyElementAttribute to a field that returns a single XmlElement object. If you do so, you must use the properties and methods of the XmlElement class to recursively iterate through the unknown elements.
Once the attribute is applied, the Baz property will correctly capture both the <Baz/> and <Baz></Baz> elements without interfering with deserialization of subsequent node(s). It does seem odd that [XmlElement("Baz")] causes the inconsistency you are seeing, but since [XmlAnyElement("Baz")] is designed to handle this situation it should be used instead.
Sample working .Net fiddle here.
I have an XML document, and using deserialization, is there a way to combine two elements into one object?
XML example:
<Parameter1>3</Parameter1>
<Parameter2>4</Parameter2>
I want to create a list (of type Parameter) that contains both items, 3 and 4.
I've tried using XmlArrayItem such as:
[XmlArrayItem("Parameter1")]
[XmlArrayItem("Parameter2")]
[XmlArray]
public Parameter[] Parameters; // have also tried this as public List<Parameter> Parameters = new List<Parameter>();
I've tried using XmlElements (but I can't figure out how to combine them):
[XmlElement("Parameter1")]
public List<Parameter> Parameters = new List<Parameter>();
Is there any way to do this without just creating two separate lists and combining them at a later point?
Please note that changing the XML format is not an option.
Your XML has a schema that includes a choice element. A choice element indicates that one of a fixed set of elements -- <Parameter1> and <Parameter2> in your case -- will occur in the XML. XmlSerializer supports choice elements as is explained in Choice Element Binding Support:
If individual choice elements' types differ along with their names, Xsd.exe applies only XmlElementAttribute attributes to a public member. If they differ only by name, Xsd.exe applies an XmlChoiceIdentifierAttribute in addition, and adds extra logic for making the choice.
Thus, you have the following options to deserialize your XML:
Subclass your Parameter class and specify different types for each element name, using [XmlElementAttribute(String, Type)]. The specific Parameter subclass instantiated would thereby capture the XML element name.
I.e. you could do:
public abstract class Parameter
{
[XmlText]
public string Value { get; set; } // Could be int if you prefer.
}
public class Parameter1 : Parameter
{
}
public class Parameter2 : Parameter
{
}
[XmlType("Root")]
public class RootObject
{
[XmlElement("Parameter1", typeof(Parameter1))]
[XmlElement("Parameter2", typeof(Parameter2))]
public Parameter[] Parameters { get; set; }
}
If you want to use the same Parameter type to deserialize both <Parameter1> and <Parameter2> elements, you must introduce an ancillary XmlChoiceIdentifierAttribute array to capture the XML element name:
public class Parameter
{
[XmlText]
public string Value { get; set; }
}
[XmlType("Root")]
public class RootObject
{
[XmlElement("Parameter1", typeof(Parameter))]
[XmlElement("Parameter2", typeof(Parameter))]
[XmlChoiceIdentifier("ParametersElementName")]
public Parameter[] Parameters { get; set; }
[XmlIgnore]
public ParametersChoiceType[] ParametersElementName { get; set; }
}
[XmlType(IncludeInSchema = false)]
public enum ParametersChoiceType
{
Parameter1,
Parameter2,
}
After deserialization, the ParametersElementName array will have the same number of entries as the Parameters array, and the enum values therein will indicate the XML element name actually encountered for each parameter.
As a variation of option 2, if you do not need to capture the XML element name and just want to deserialize the values, you could create a "fake" choice array property as follows:
[XmlType("Root")]
public class RootObject
{
[XmlElement("Parameter1", typeof(Parameter))]
[XmlElement("Parameter2", typeof(Parameter))]
[XmlChoiceIdentifier("ParametersElementName")]
public Parameter[] Parameters { get; set; }
[XmlIgnore]
public ParametersChoiceType[] ParametersElementName
{
get
{
if (Parameters == null)
return null;
return Parameters.Select(p => ParametersChoiceType.Parameter1).ToArray();// Arbitrarily return ItemsChoiceType.Parameter1
}
set
{
// Do nothing - don't care.
}
}
}
XmlSerializer requires you to use one of these two options. If it cannot determine a correct element name by type or by item choice identifier, it will throw an InvalidOperationException with the message:
You need to add XmlChoiceIdentifierAttribute to the 'Parameters' member.
Prototype fiddle showing each option.
What if you do something like this:
//get the xml doc
const string str = #"<root>
<Parameter1>3</Parameter1>
<Parameter2>4</Parameter2>
</root>";
var xml = new XmlDocument();
//load it
xml.LoadXml(str);
//get the nodes where the names contain the string parameter
var xnList = xml.SelectNodes("//*[contains(name(),'Parameter')]");
//create a list of parameters
var list = new List<Parameter>();
//populate the list with the value in the node's innertext
foreach (XmlNode xn in xnList)
{
list.Add(new Parameter{ Value = int.Parse(xn.InnerText) } );
}
foreach(var param in list)
Console.WriteLine(param.Value); //should print 3 and 4
I am using this class as an example:
class Parameter{
public int Value { get; set; }
}
Say we have a class like:
using System;
using System.Xml.Serialization;
namespace XmlEntities {
[XmlRoot("Agent")]
public class RootClass {
private string element_description;
[XmlElement("Name")]
public string Name{ get; set; }
}
[XmlElement("Surname")]
public string Surname{ get; set; }
}
}
And we want to serialize into xml only Name XmlElement. How to limit that at serialization?
Have you encountered the [XmlIgnore] attribute? Adding it to members of your class will exclude them from serialization.
So, for example, you can replace [XmlElement("Surname")] with [XmlIgnore], and then your serialized agent will look like this:
<Agent>
<Name>John Doe</Name>
</Agent>
Alternately, if all you really want is just <Name>John Doe</Name>, you could write a wrapper class:
[XmlRoot("Name")]
public class NameElement
{
[XmlText]
public string Name { get; set; }
}
* EDIT *
While it's possible to generate such wrappers at runtime, it's difficult, inefficient, and not very practical.
To do so, I guess you could reflectively examine your object and find the properties you want (root.GetType().GetProperties().Where(p => /* your logic here */)), and use System.Reflection.Emit to generate the appropriate class. While possible, it's not reasonable - it'd be a huge amount of code relative to your actual logic, and you could easily destabilize the runtime and/or leak memory.
A better way to achieve the dynamicism you want is to forego System.Xml.Serialization and use System.Xml.Linq. This would require you to write code that built up the xml yourself, but it's super easy:
public XElement ConvertToXml(RootClass root)
{
return new XElement("Name", root.Name);
}
You can write an XElement to any stream using the element.Save(Stream) instance method on XElement.
Read more about Linq to XML at MSDN
If you want to ignore the element at runtime, at serialization, you can use XmlAttributeOverrides:
XmlAttributeOverrides overrides = new XmlAttributeOverrides();
XmlAttributes attribs = new XmlAttributes();
attribs.XmlIgnore = true;
attribs.XmlElements.Add(new XmlElementAttribute("Surname"));
overrides.Add(typeof(RootClass), "Surname", attribs);
XmlSerializer ser = new XmlSerializer(typeof(RootClass), overrides);
RootClass agent = new RootClass();
agent.Name = "Marc";
agent.Surname = "Jobs";
ser.Serialize(Console.Out, agent);