XmlSerializer - There was an error reflecting type

akantro_4653 0
Viewed 264959

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?

.net-2.0 serialization xml .net c#
19 Answers

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.

user_35660

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.

user_35460
Rob_Cooper_8320
Gulzar_43370

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.

user_379710

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.

user_442470

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.

Darren_60650

Sometime, this type of error is because you dont have constructur of class without argument

user_37356900

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; }
user_75966960

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.

user_62760

I have been using the NetDataSerialiser class to serialise my domain classes. NetDataContractSerializer Class.

The domain classes are shared between client and server.

Admin1

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");
    }
}
user_48712630
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