I have a custom base class Entity decorated with [DataContract(IsReference = true)] and deriving from UndoableBase of CSLA.net. Keeping IsReference is important to preserve object reference data.
[Serializable]
[DataContract(IsReference = true)]
public abstract class Entity : UndoableBase
I am getting exception upon serialization using below code snippet:
public void SerializeToFile(string fileName, T obj)
{
_serializer = new DataContractSerializer(typeof(T));
Serialize(fileName, obj);
}
private void Serialize(string fileName, T obj)
{
using (var fs = File.Open(fileName, FileMode.Create))
{
_serializer.WriteObject(fs, obj);
fs.Close();
}
}
System.Runtime.Serialization.InvalidDataContractException
The IsReference setting for type 'Entity' is 'True', but the same
setting for its parent class 'Csla.Core.UndoableBase' is 'False'.
Derived types must have the same value for IsReference as the base
type. Change the setting on type 'Entity' to 'False', or on type
'Csla.Core.UndoableBase' to 'True', or do not set IsReference
explicitly.
If I remove this IsReference attribute altogether I start getting following error:
Object graph for type 'XYZ' contains cycles and cannot be serialized
if reference tracking is disabled.
Now my question is how to solve it by changing the IsReference setting for Csla.Core.UndoableBase during serialization using some API.
While researching on this topic I came across this post, which talks about using DataContractSurrogate. Please help how to use it specifically if it is helpful in this case or suggest any other technique solving it.
How to serialize class that derives from class decorated with DataContract(IsReference=true)?
After quite a struggle I was finally able to find the answer to this question. There is an overloaded constructor which takes preserveObjectReferences flag to instruct the serializer to preserve the References. In my case, I have now removed IsReference annotation from all over and used below overload for serialization and life is good.
var serializer = new DataContractSerializer(typeof(T), knownTypes,
int.MaxValue /*maxObjectsInGraph*/,
false /*ignoreExtensionDataObject*/,
true /*preserveObjectReferences*/,
null /*dataContractSurrogate*/);
Reference: Preserving Object Reference in WCF
Related
I am trying to serialize an object graph. It works up until I have to load a child entity that is an entity set. The system won't allow it to serialize... it gives me this error:
Type 'System.Data.Linq.EntitySet`1[NetDataContractSerializerTest.JobService]' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. If the type is a collection, consider marking it with the CollectionDataContractAttribute. See the Microsoft .NET Framework documentation for other supported types.
Here is the code I am using:
DataClasses1DataContext dataAccessContext = new DataClasses1DataContext();
MemoryStream stream = new MemoryStream();
DataLoadOptions dataloadOptions = new DataLoadOptions();
dataloadOptions.LoadWith<JN>(j => j.nh);
dataloadOptions.LoadWith<JN>(j => j.JobServices);// this is the child entity set
dataAccessContext.LoadOptions = dataloadOptions;
var jn= dataAccessContext.JN.Where(j => j.LocnID.Trim() == "HT").ToList();
var netDataContractSerializer = new NetDataContractSerializer();
netDataContractSerializer.Serialize(stream, jn); //the error happens here
If I remove the
dataloadOptions.LoadWith(j => j.JobServices)
the data will serialize with the JN and nh tables intact. But when I put
dataloadOptions.LoadWith(j => j.JobServices)
back in I get the error.
I personally think that it wants me to add a ToList() to the JobServices, unfortunately I can't do
dataloadOptions.LoadWith(j => j.JobServices.ToList())
This throws an error.
Any ideas?
The error message is very informative: the JobService class is not marked to be serialized as a data contract.
You'll need to decorate it with the DataContractAttribute attribute, and decorate the members with DataMember attribute.
[DataContract]
public class JobService
{
[DataMember]
public string SomeProperty { get; set;}
}
Well well well.... look what I found..... This seemed to serialize and deserialize my stuff just fine. Instead of using NetDataContractSerializer.Serialize() to it, this guy wrote serialize and deserialize functions that used DataContractSerializer, XMLWriter and XMLReader
Check the link below
http://www.codeproject.com/Tips/47054/How-to-serialize-list-of-linq-entities-ex-from-DBM
I have a complex model serialized/deserialized with protobuf-net, and we had several bugs with this "feature" of not serializing default values.
Example:
[DataContract]
class Foo{
public Foo(){
// Value forced by constructor
this.Value = 1;
}
// Buggy, when Value is set to zero
[DataMember(Order = 1)]
public double Value {get; set}
}
When Value = 0, it is not serialized by protobuf-net, but during deserialization, the constructor forces Value to 1 (and protobuf-net do not change this).
In order to make it work, I need to force protobuf-net to serialize values, with:
// Works fine
[DataMember(Order = 1, IsRequired = true)]
public double Value {get; set}
But, as we already got bugs because of this feature, we'd like to force protobuf-net for the whole model, instead of marking every property.
Is it possible?
Yes, this feature is fully supported. Actually, if I was forced to admit to bad design decisions in v1, the implicit-zero-defaults would be one of them - but for backwards compatibility the behaviour is retained by default. What you are looking for is RuntimeTypeModel.UseImplicitZeroDefaults, which is true by default.
To avoid changing the behaviour of code relying on v1 behaviour (via Serilaizer.*), you cannot change this feature on the default model, so what you need to do is:
define your own model/serializer-instance
set UseImplicitZeroDefaults = false, before using it
in your serialize/deserialize code, use this instance rather than Serializer.*
for example:
private static readonly RuntimeTypeModel serializer;
static MyType() { // your type-initializer for class MyType
serializer = TypeModel.Create();
serializer.UseImplicitZeroDefaults = false;
}
... then when needed:
serializer.Serialize(stream, obj);
...
ObjType obj = (ObjType)serializer.Deserialize(stream, null, typeof(ObjType));
Another approach I could perhaps consider in the future is allowing for assembly-level attributes; this would help in particular for anyone using "precompiler" (for example, targeting mobile devices or WinRT) - so (just thinking aloud):
// this feature ***does not currently exist***
[assembly:ProtoDefaults(UseImplicitZeroDefaults=false, SkipConstructor=true)]
which would then apply to all types in that assembly. Just a thought. Another obvious advantage is that it would work with code that uses the classic Serializer.* API.
I have an application with plugin architecture. The plugins have their own data containers, which all inherit from the base interface IPluginDataStorage. The DataStorage object, which is serialized to preserve state, contains a list of these subclasses along with other data. The DynamicType flag is set to true, as it's not known until run time which plugins are in use.
[Serializable]
[ProtoContract]
public class DataStorage
{
[ProtoMember(200, DynamicType = true)]
public List<IPluginDataContainer> PluginDataStorage { get; set; }
When serializing this setup works okay, but I'm having problems deserializing the list reliably. If I try to deserialize the object without having access to all those plugins that were used when it was serialized, I, naturally, get an exception about a missing type.
Unable to resolve type: NOSMemoryConsumptionPlugin.NOSMemoryConsumptionData, NOSMemoryConsumptionPlugin, Version=1.2.0.17249, Culture=neutral, PublicKeyToken=null (you can use the TypeModel.DynamicTypeFormatting event to provide a custom mapping)
The exception gives a hint that I could provide the format through the event, but I don't see how that could be helpful as the problem is that I don't have that type available. What I'd like to do in these cases is to completely ignore deserializing that object. The list item could even default to a dummy instance of the base class in these cases. But how to do this?
That (choosing to skip or default) is a fascinating use-case that I don't think I have considered fully; however, you can probably do this yourself, via:
public class NilContainer : IPluginDataContainer {}
and then subscribe to the DynamicTypeFormatting event; if you don't recognise the type, supply typeof(NilContainer).
i.e.
RuntimeTypeModel.Default.DynamicTypeFormatting += (sender, args) =>
{
Type type;
if(!yourTypeMap.TryGetValue(args.FormattedName, out type))
{
type = typeof (NilContainer);
}
args.Type = type;
};
(completely untested)
Using C# .NET 2.0, I have a composite data class that does have the [Serializable] attribute on it. I am creating an XMLSerializer class and passing that into the constructor:
XmlSerializer serializer = new XmlSerializer(typeof(DataClass));
I am getting an exception saying:
There was an error reflecting type.
Inside the data class there is another composite object. Does this also need to have the [Serializable] attribute, or by having it on the top object, does it recursively apply it to all objects inside?
Look at the inner exception that you are getting. It will tell you which field/property it is having trouble serializing.
You can exclude fields/properties from xml serialization by decorating them with the [XmlIgnore] attribute.
XmlSerializer does not use the [Serializable] attribute, so I doubt that is the problem.
Remember that serialized classes must have default (i.e. parameterless) constructors. If you have no constructor at all, that's fine; but if you have a constructor with a parameter, you'll need to add the default one too.
I had a similar problem, and it turned out that the serializer could not distinguish between 2 classes I had with the same name (one was a subclass of the other). The inner exception looked like this:
'Types BaseNamespace.Class1' and 'BaseNamespace.SubNamespace.Class1' both use the XML type name, 'Class1', from namespace ''. Use XML attributes to specify a unique XML name and/or namespace for the type.
Where BaseNamespace.SubNamespace.Class1 is a subclass of BaseNamespace.Class1.
What I needed to do was add an attribute to one of the classes (I added to the base class):
[XmlType("BaseNamespace.Class1")]
Note: If you have more layers of classes you need to add an attribute to them as well.
Most common reasons by me:
- the object being serialized has no parameterless constructor
- the object contains Dictionary
- the object has some public Interface members
Also be aware that XmlSerializer cannot serialize abstract properties.. See my question here (which I have added the solution code to)..
XML Serialization and Inherited Types
All the objects in the serialization graph have to be serializable.
Since XMLSerializer is a blackbox, check these links if you want to debug further into the serialization process..
Changing where XmlSerializer Outputs Temporary Assemblies
HOW TO: Debug into a .NET XmlSerializer Generated Assembly
If you need to handle specific attributes (i.e. Dictionary, or any class), you can implement the IXmlSerialiable interface, which will allow you more freedom at the cost of more verbose coding.
public class NetService : IXmlSerializable
{
#region Data
public string Identifier = String.Empty;
public string Name = String.Empty;
public IPAddress Address = IPAddress.None;
public int Port = 7777;
#endregion
#region IXmlSerializable Implementation
public XmlSchema GetSchema() { return (null); }
public void ReadXml(XmlReader reader)
{
// Attributes
Identifier = reader[XML_IDENTIFIER];
if (Int32.TryParse(reader[XML_NETWORK_PORT], out Port) == false)
throw new XmlException("unable to parse the element " + typeof(NetService).Name + " (badly formatted parameter " + XML_NETWORK_PORT);
if (IPAddress.TryParse(reader[XML_NETWORK_ADDR], out Address) == false)
throw new XmlException("unable to parse the element " + typeof(NetService).Name + " (badly formatted parameter " + XML_NETWORK_ADDR);
}
public void WriteXml(XmlWriter writer)
{
// Attributes
writer.WriteAttributeString(XML_IDENTIFIER, Identifier);
writer.WriteAttributeString(XML_NETWORK_ADDR, Address.ToString());
writer.WriteAttributeString(XML_NETWORK_PORT, Port.ToString());
}
private const string XML_IDENTIFIER = "Id";
private const string XML_NETWORK_ADDR = "Address";
private const string XML_NETWORK_PORT = "Port";
#endregion
}
There is an interesting article, which show an elegant way to implements a sophisticated way to "extend" the XmlSerializer.
The article say:
IXmlSerializable is covered in the official documentation, but the documentation states it's not intended for public use and provides no information beyond that. This indicates that the development team wanted to reserve the right to modify, disable, or even completely remove this extensibility hook down the road. However, as long as you're willing to accept this uncertainty and deal with possible changes in the future, there's no reason whatsoever you can't take advantage of it.
Because this, I suggest to implement you're own IXmlSerializable classes, in order to avoid too much complicated implementations.
...it could be straightforward to implements our custom XmlSerializer class using reflection.
I just got the same error and discovered that a property of type IEnumerable<SomeClass> was the problem. It appears that IEnumerable cannot be serialized directly.
Instead, one could use List<SomeClass>.
I've discovered that the Dictionary class in .Net 2.0 is not serializable using XML, but serializes well when binary serialization is used.
I found a work around here.
I recently got this in a web reference partial class when adding a new property. The auto generated class was adding the following attributes.
[System.Xml.Serialization.XmlElementAttribute(Order = XX)]
I needed to add a similar attribute with an order one higher than the last in the auto generated sequence and this fixed it for me.
I too thought that the Serializable attribute had to be on the object but unless I'm being a complete noob (I am in the middle of a late night coding session) the following works from the SnippetCompiler:
using System;
using System.IO;
using System.Xml;
using System.Collections.Generic;
using System.Xml.Serialization;
public class Inner
{
private string _AnotherStringProperty;
public string AnotherStringProperty
{
get { return _AnotherStringProperty; }
set { _AnotherStringProperty = value; }
}
}
public class DataClass
{
private string _StringProperty;
public string StringProperty
{
get { return _StringProperty; }
set{ _StringProperty = value; }
}
private Inner _InnerObject;
public Inner InnerObject
{
get { return _InnerObject; }
set { _InnerObject = value; }
}
}
public class MyClass
{
public static void Main()
{
try
{
XmlSerializer serializer = new XmlSerializer(typeof(DataClass));
TextWriter writer = new StreamWriter(#"c:\tmp\dataClass.xml");
DataClass clazz = new DataClass();
Inner inner = new Inner();
inner.AnotherStringProperty = "Foo2";
clazz.InnerObject = inner;
clazz.StringProperty = "foo";
serializer.Serialize(writer, clazz);
}
finally
{
Console.Write("Press any key to continue...");
Console.ReadKey();
}
}
}
I would imagine that the XmlSerializer is using reflection over the public properties.
Sometime, this type of error is because you dont have constructur of class without argument
I had a situation where the Order was the same for two elements in a row
[System.Xml.Serialization.XmlElementAttribute(IsNullable = true, Order = 0, ElementName = "SeriousInjuryFlag")]
.... some code ...
[System.Xml.Serialization.XmlElementAttribute(IsNullable = true, Order = 0, ElementName = "AccidentFlag")]
When I changed the code to increment the order by one for each new Property in the class, the error went away.
I was getting the same error when I created a property having a datatype - Type. On this, I was getting an error - There was an error reflecting type. I kept checking the 'InnerException' of every exception from the debug dock and got the specific field name (which was Type) in my case. The solution is as follows:
[XmlIgnore]
public Type Type { get; set; }
Also note that you cannot serialize user interface controls and that any object you want to pass onto the clipboard must be serializable otherwise it cannot be passed across to other processes.
I have been using the NetDataSerialiser class to serialise
my domain classes. NetDataContractSerializer Class.
The domain classes are shared between client and server.
I had the same issue and in my case the object had a ReadOnlyCollection. A collection must implement Add method to be serializable.
I have a slightly different solution to all described here so far, so for any future civilisation here's mine!
I had declared a datatype of "time" as the original type was a TimeSpan and subsequently changed to a String:
[System.Xml.Serialization.XmlElementAttribute(DataType="time", Order=3)]
however the actual type was a string
public string TimeProperty {
get {
return this.timePropertyField;
}
set {
this.timePropertyField = value;
this.RaisePropertyChanged("TimeProperty");
}
}
by removing the DateType property the Xml can be serialized
[System.Xml.Serialization.XmlElementAttribute(Order=3)]
public string TimeProperty {
get {
return this.timePropertyField;
}
set {
this.timePropertyField = value;
this.RaisePropertyChanged("TimeProperty");
}
}
[System.Xml.Serialization.XmlElementAttribute("strFieldName", Form = System.Xml.Schema.XmlSchemaForm.Unqualified)]
Or
[XmlIgnore]
string [] strFielsName {get;set;}
Using C# .NET 2.0, I have a composite data class that does have the [Serializable] attribute on it. I am creating an XMLSerializer class and passing that into the constructor:
XmlSerializer serializer = new XmlSerializer(typeof(DataClass));
I am getting an exception saying:
There was an error reflecting type.
Inside the data class there is another composite object. Does this also need to have the [Serializable] attribute, or by having it on the top object, does it recursively apply it to all objects inside?
Look at the inner exception that you are getting. It will tell you which field/property it is having trouble serializing.
You can exclude fields/properties from xml serialization by decorating them with the [XmlIgnore] attribute.
XmlSerializer does not use the [Serializable] attribute, so I doubt that is the problem.
Remember that serialized classes must have default (i.e. parameterless) constructors. If you have no constructor at all, that's fine; but if you have a constructor with a parameter, you'll need to add the default one too.
I had a similar problem, and it turned out that the serializer could not distinguish between 2 classes I had with the same name (one was a subclass of the other). The inner exception looked like this:
'Types BaseNamespace.Class1' and 'BaseNamespace.SubNamespace.Class1' both use the XML type name, 'Class1', from namespace ''. Use XML attributes to specify a unique XML name and/or namespace for the type.
Where BaseNamespace.SubNamespace.Class1 is a subclass of BaseNamespace.Class1.
What I needed to do was add an attribute to one of the classes (I added to the base class):
[XmlType("BaseNamespace.Class1")]
Note: If you have more layers of classes you need to add an attribute to them as well.
Most common reasons by me:
- the object being serialized has no parameterless constructor
- the object contains Dictionary
- the object has some public Interface members
Also be aware that XmlSerializer cannot serialize abstract properties.. See my question here (which I have added the solution code to)..
XML Serialization and Inherited Types
All the objects in the serialization graph have to be serializable.
Since XMLSerializer is a blackbox, check these links if you want to debug further into the serialization process..
Changing where XmlSerializer Outputs Temporary Assemblies
HOW TO: Debug into a .NET XmlSerializer Generated Assembly
If you need to handle specific attributes (i.e. Dictionary, or any class), you can implement the IXmlSerialiable interface, which will allow you more freedom at the cost of more verbose coding.
public class NetService : IXmlSerializable
{
#region Data
public string Identifier = String.Empty;
public string Name = String.Empty;
public IPAddress Address = IPAddress.None;
public int Port = 7777;
#endregion
#region IXmlSerializable Implementation
public XmlSchema GetSchema() { return (null); }
public void ReadXml(XmlReader reader)
{
// Attributes
Identifier = reader[XML_IDENTIFIER];
if (Int32.TryParse(reader[XML_NETWORK_PORT], out Port) == false)
throw new XmlException("unable to parse the element " + typeof(NetService).Name + " (badly formatted parameter " + XML_NETWORK_PORT);
if (IPAddress.TryParse(reader[XML_NETWORK_ADDR], out Address) == false)
throw new XmlException("unable to parse the element " + typeof(NetService).Name + " (badly formatted parameter " + XML_NETWORK_ADDR);
}
public void WriteXml(XmlWriter writer)
{
// Attributes
writer.WriteAttributeString(XML_IDENTIFIER, Identifier);
writer.WriteAttributeString(XML_NETWORK_ADDR, Address.ToString());
writer.WriteAttributeString(XML_NETWORK_PORT, Port.ToString());
}
private const string XML_IDENTIFIER = "Id";
private const string XML_NETWORK_ADDR = "Address";
private const string XML_NETWORK_PORT = "Port";
#endregion
}
There is an interesting article, which show an elegant way to implements a sophisticated way to "extend" the XmlSerializer.
The article say:
IXmlSerializable is covered in the official documentation, but the documentation states it's not intended for public use and provides no information beyond that. This indicates that the development team wanted to reserve the right to modify, disable, or even completely remove this extensibility hook down the road. However, as long as you're willing to accept this uncertainty and deal with possible changes in the future, there's no reason whatsoever you can't take advantage of it.
Because this, I suggest to implement you're own IXmlSerializable classes, in order to avoid too much complicated implementations.
...it could be straightforward to implements our custom XmlSerializer class using reflection.
I just got the same error and discovered that a property of type IEnumerable<SomeClass> was the problem. It appears that IEnumerable cannot be serialized directly.
Instead, one could use List<SomeClass>.
I've discovered that the Dictionary class in .Net 2.0 is not serializable using XML, but serializes well when binary serialization is used.
I found a work around here.
I recently got this in a web reference partial class when adding a new property. The auto generated class was adding the following attributes.
[System.Xml.Serialization.XmlElementAttribute(Order = XX)]
I needed to add a similar attribute with an order one higher than the last in the auto generated sequence and this fixed it for me.
I too thought that the Serializable attribute had to be on the object but unless I'm being a complete noob (I am in the middle of a late night coding session) the following works from the SnippetCompiler:
using System;
using System.IO;
using System.Xml;
using System.Collections.Generic;
using System.Xml.Serialization;
public class Inner
{
private string _AnotherStringProperty;
public string AnotherStringProperty
{
get { return _AnotherStringProperty; }
set { _AnotherStringProperty = value; }
}
}
public class DataClass
{
private string _StringProperty;
public string StringProperty
{
get { return _StringProperty; }
set{ _StringProperty = value; }
}
private Inner _InnerObject;
public Inner InnerObject
{
get { return _InnerObject; }
set { _InnerObject = value; }
}
}
public class MyClass
{
public static void Main()
{
try
{
XmlSerializer serializer = new XmlSerializer(typeof(DataClass));
TextWriter writer = new StreamWriter(#"c:\tmp\dataClass.xml");
DataClass clazz = new DataClass();
Inner inner = new Inner();
inner.AnotherStringProperty = "Foo2";
clazz.InnerObject = inner;
clazz.StringProperty = "foo";
serializer.Serialize(writer, clazz);
}
finally
{
Console.Write("Press any key to continue...");
Console.ReadKey();
}
}
}
I would imagine that the XmlSerializer is using reflection over the public properties.
Sometime, this type of error is because you dont have constructur of class without argument
I had a situation where the Order was the same for two elements in a row
[System.Xml.Serialization.XmlElementAttribute(IsNullable = true, Order = 0, ElementName = "SeriousInjuryFlag")]
.... some code ...
[System.Xml.Serialization.XmlElementAttribute(IsNullable = true, Order = 0, ElementName = "AccidentFlag")]
When I changed the code to increment the order by one for each new Property in the class, the error went away.
I was getting the same error when I created a property having a datatype - Type. On this, I was getting an error - There was an error reflecting type. I kept checking the 'InnerException' of every exception from the debug dock and got the specific field name (which was Type) in my case. The solution is as follows:
[XmlIgnore]
public Type Type { get; set; }
Also note that you cannot serialize user interface controls and that any object you want to pass onto the clipboard must be serializable otherwise it cannot be passed across to other processes.
I have been using the NetDataSerialiser class to serialise
my domain classes. NetDataContractSerializer Class.
The domain classes are shared between client and server.
I had the same issue and in my case the object had a ReadOnlyCollection. A collection must implement Add method to be serializable.
I have a slightly different solution to all described here so far, so for any future civilisation here's mine!
I had declared a datatype of "time" as the original type was a TimeSpan and subsequently changed to a String:
[System.Xml.Serialization.XmlElementAttribute(DataType="time", Order=3)]
however the actual type was a string
public string TimeProperty {
get {
return this.timePropertyField;
}
set {
this.timePropertyField = value;
this.RaisePropertyChanged("TimeProperty");
}
}
by removing the DateType property the Xml can be serialized
[System.Xml.Serialization.XmlElementAttribute(Order=3)]
public string TimeProperty {
get {
return this.timePropertyField;
}
set {
this.timePropertyField = value;
this.RaisePropertyChanged("TimeProperty");
}
}
[System.Xml.Serialization.XmlElementAttribute("strFieldName", Form = System.Xml.Schema.XmlSchemaForm.Unqualified)]
Or
[XmlIgnore]
string [] strFielsName {get;set;}