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Cannot serialize member ... because it implements IDictionary

Cat de cunoscuta vi se pare urmatoarea eroare:
Cannot serialize member [FooMember]
... because it implements IDictionary.
Primul lucru pe care oamenii il spun cand intalnesc aceasta eroare este: "Pai logic ca crapa, un dictionar nu e serializabil". Da, intr-o oarecare masura enuntul de mai sus este adevarat, dar nu in totalitate.
Nu toate serializatoarele sunt capabile sa serializeze un IDictionary. Cele mai dese probleme de acest gen apare cand se lucreaza cu XmlSerializer. Trebuie tinut cont ca aceasta problema nu apare la serializare ci la deserializare. Deserializatorul nu stie cu ce obiecte lucreaza, nu gaseste nici o informatie despre tipul lor.
O solutie destul de simpla, care este la indemana oricui este sa folosim DataContractSerializer pentru a serializa/deserializa un dictionar. Schimbariile care trebuie facute pentru a trece de la XmlSerializer la DataContractSerializer sunt destul de putin.
Primul pas este sa marcam clasa pe care o dorim sa o serializam cu DataContract, iar toate elementele pe care dorim sa le serializam cu atributul DataMember. Acest pas nu este obligatoriu pentru .NET 3.5 SP1 +. Daca folositi .NET 3.5 SP1, .NET 4.0 sau .NET 4.5 acest pas este optional. By default tot ce e public se serializare. In cazul in care aveti propietati pe care nu vreti sa le serializati, este nevoie sa adaugati aceste atribute.
Urmatorul pas este sa folosim pentru serializare si deserializare DataContractSerializer, iar metodele Serializer si Deserialize o sa fie inlocuite cu WriteObject si ReadObject.
Mai jos puteti sa gasiti un exemplu de cod in C# 4.5 care poate sa fie folosit pe Windows 8 Metro Style App fara nici o problema:
// Serialize
using (MemoryStream stream = new MemoryStream())
{
DataContractSerializer serializer = new DataContractSerializer(obj.GetType());
using (StreamWriter streamWriter = new StreamWriter(stream, _encoder.Current))
{
using (XmlWriter xmlWriter = XmlWriter.Create(streamWriter))
{
serializer.WriteObject(xmlWriter, obj);
xmlWriter.Flush();
}
stream.Seek(0, SeekOrigin.Begin);
// TODO: save or manipulate streamWriter
}
}
// Deserialize
using (StringReader reader = new StringReader(_encoder.ToString(content)))
{
XmlReader xmlReader = XmlReader.Create(reader);
XmlSerializer serializer = GetSerializer(typeof (TEntity));

return (TEntity) serializer.Deserialize(xmlReader);
}
Daca am fi fost intr-o aplicatie non-metro style am fi putut lucra cu XmlTextWriter unde sa avem propietatea Formatting setata cu valoare Formating.Indented. In acest caz XML generat ar fi fost mult mai usor de citit de catre oameni. Dar putem sa traim fara nici o problema fara aceasta optiune.
Enjoy!

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