i hope this is not a repeated question.
I've a class like this :
[Serializable]
class MyClass
{
int type;
List <FileStream> listfile;
string content_text;
public MyClass(int t)
{
type = t;
}
public MyClass()
{
type = 0;
}
}
i need to send an object of Myclass in a Socket with the method Socket.Send(byte []).
So i've to serialize this object. But also if i add [Serializable], FileStream isn't serializable, and i get an exception runtime.
Someone can help me ?
Thank you very much.
When you add Serializable to a class it doesn't change anything, it simply just tells the CLR that your class can be serialized.
Beacuse of this, any classes that are part of an object and are not by default Serializable will not get changed in anyway, and as such will cause the exception you see when you attempt to.
The following link will show you the MSDN documentation for the Serializable attribute :
http://msdn.microsoft.com/en-us/library/system.serializableattribute(v=vs.110).aspx
You can however mark individual properties in your class as not serializable by using the 'NonSerializedAttribute' as follows:
[Serializable]
class MyClass
{
int type;
[NonSerialized]
List<FileStream> listfile;
string content_text;
public MyClass(int t)
{
type = t;
}
public MyClass()
{
type = 0;
}
}
This will prevent the exception occurring, BUT it will do so by removing the actual property from the serialized output, which means if your wanting to pass the filestream objects over your socket, then your fresh out of luck unfortunately because your just not going to be able to.
Now, that said, you can attempt to read the contents of the file stream(s) into byte arrays, and you could then easily send those byte arrays as 'byte[]' is serializable without any issues.
I would however recommend that if your going to start sending byte[] arrays of arbitrary length over a socket, that you look at using a binary streaming protocol (Perhaps Google Proto Buffers) rather than the default text serialized objects you get out of the box.
Related
I have a library of fairly heavy-weight DTOs that is currently being used by some WCF services. We are attempting to bring it into protobuf-net world, with as little modification as possible. One particular set of items is giving me trouble in serialization. I'm going to simply them here because it gets a little complicated, but the gist of the problem is:
public class Key
{
public string Id {get; set;}
}
public class KeyCollection : IEnumerable<Key>
{
private readonly List<Key> list;
#region IEnumerable
// etc...
#endregion
}
public class Item
{
public long Id { get; set; }
}
public abstract class ContainerBase
{ }
public abstract class ContainerBase<T> : ContainerBase
where T : Item
{ }
public abstract class ContainerType1Base : ContainerBase<Item>
{
public KeyCollection Keys { get; set; }
}
public class ContainerType1 : ContainerType1Base
{ }
I've left out the decorators because I don't they're the problem, mostly because if I add void Add(Key item) { } to KeyCollection the whole thing seems to work. Otherwise, I run into problems attempting to serialize an instance of ContainerType1.
Actually, changing the signature of KeyCollection is kind of prohibitive, so I'm attempting to follow this answer to try to do it programatically. Specifically, setting itemType and defaultType to null on the "Keys" ValueMember of ContainerType1, ContainerType1Base and ContainerBase<Item>. I also set IgnoreListHandling to true on KeyCollection... which totally doesn't work. I get a generic "failed to deserialize" exception on the client, which I can post here if it would help. On the server side, I serialize it out using Serializer.Serialize(), and I spit out Serializer.GetProto<>() as well as JSON of the object, and they all seem to be work okay.
How can I turn off the list handling? Related to that, is there a way to turn on extra debugging while serializing to try to get some more information of the problem?
Fundamentally, the code shown looks fine. Unfortunately, there's currently a "feature" in gRPC that means that it discards the original exception when a marshaller (serializer) fails for some reason, so gRPC does not currently expose the actual problem. I have submitted a fix for this - it may or may not be accepted.
In the interim, I suggest that you simply remove gRPC from the equation, and simulate just the marshaller workload; to do this, on the server: generate the data you are trying to send, and do:
var ms = new MemoryStream();
Serializer.Serialize(ms, yourDataHere);
var payload = Convert.ToBase64String(ms.ToArray());
and obtain the value of payload (which is just a string). Now at the client, reverse this:
var ms = new MemoryStream(Convert.FromBase64String(thatStringValue));
Serialize.Deserialize<YourTypeHere>(ms);
My expectation here is that this should throw an exception that will tell you what the actual problem is.
If the gRPC change gets merged, then the fault should be available via:
catch (RpcException fault)
{
var originalFault = fault.Status.DebugException;
// ^^^
}
I am having some trouble deserializing an object to XML. I am trying to deserialize something which doesn't have an empty constructor thus I need to use the BinaryFormatter? I have:
A DLL which consists of a class I want to deserialize into XML.
From reflecting the type I can see that it has no parameterless constructor.
This class contains properties of which some do not have empty constructors either.
My question is, is it possible to deserialize this class into XML? I did find a way whereby I used:
BinaryFormatter
Loaded the contents into a stream
Used a FileStream to write its contents but ended up with rubbish
Thanks in advance. I found something called FormatterServices... but don't know whether you could use this in conjunction with the XmlSerializer?
Deserialize the binary data back into an object.
Copy your object into a surrogate object.
Xml serialize your surrogate object.
Assume the type of your original non-xml serializable object is "Foo"
[XmlRoot]
public class FooSurrogate {
public FooSurrogate() { }; // note the empty constructor for xml deserialization
public FooSurrogate(Foo foo) { // this constructor is used in step 2
// in here you copy foo's state into this object's state
this.Prop1 = foo.Prop1; // this prop can be copied directly
this.Bar = new BarSurrogate(foo.Bar); // this prop needs a surrogate as well
}
[XmlAttribute] // note your surrogate can be used to xml-format too!
public string Prop1 { get; set; }
[XmlElement]
public BarSurrogate Bar { get; set; }
}
public class BarSurrogate {
...
}
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;}
This is one i struggled with for ages so thought I'd document somewhere. (Apologies for asking and answering a question.)
(C# .net 2.0)
I had a class that was being serialized by XmlSerializer, I added a new public property however it wasn't being included in the output XML.
It's not mentioned in the docs anywhere I could find, but public properties must have a set as well as a get to be serialized! I guess this is because it assumes that if you're going to serialize then you'll want to deserialize from the same file, so only serializes properties that have both a set and a get.
As mentioned, most properties must have both a getter and setter; the main exception to this is lists - for example:
private readonly List<Foo> bar = new List<Foo>();
public List<Foo> Bar {get { return bar; } } // works fine
which will work fine; however, if XmlSerializer finds a setter - it demands that it is public; the following will not work:
public List<Foo> Bar {get; private set;} // FAIL
Other reasons it might not serialize:
it isn't public with get and set (or is readonly for a field)
it has a [DefaultValue] attribute, and is with that value
it has a public bool ShouldSerializeFoo() method that returned false
it has a public bool FooSpecified {get;set;} property or field that returned false
it is marked [XmlIgnore]
it is marked [Obsolete]
Any of these will cause it not to serialize
The point about getter+setter is made in the 3rd paragraph on the "Intro to Xml Serialization" page. It's actually in a call-out box. Can't miss it!
Intro-to-XML Serialization http://www.freeimagehosting.net/uploads/2f04fea2db.png
(having a little too much fun with Freeimagehosting.net)
Also properties that return null are not serialized!
if you don't want to implement proper Setters (because maybe you are neither wanting to deserialize or change an objects value) you can just use dummy setters like this set { }, so that the XMLSerializer works, but nothing happens if you use the Setter...
i.E.
public string ID { get { return _item.ID.ToString(); } set { } }
And if your class inherits a list and also has its own members, only the elements of the list get serialized. The data present in your class members is not captured.
Took some time figuring out this!
One more thing to add about serialization of collections:
The XmlSerializer ignores collections of interfaces!
And by that I mean ignore. While you will get an exception for a line like:
public IFoo Foo { get; set; }
you will not get an exception for:
public ICollection<IFoo> LotsOfFoos { get { return this.fooBackingField; } }
You can implement the IXmlSerializer and do the serialization manually, and benefit from serializing properties, and vice versa, deserializing them using constructors / private field assignment.
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;}