Skip to main content

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);
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.


Popular posts from this blog

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

Entity Framework (EF) TransactionScope vs Database.BeginTransaction

In today blog post we will talk a little about a new feature that is available on EF6+ related to Transactions.
Until now, when we had to use transaction we used ‘TransactionScope’. It works great and I would say that is something that is now in our blood.
using (var scope = new TransactionScope(TransactionScopeOption.Required)) { using (SqlConnection conn = new SqlConnection("...")) { conn.Open(); SqlCommand sqlCommand = new SqlCommand(); sqlCommand.Connection = conn; sqlCommand.CommandText = ... sqlCommand.ExecuteNonQuery(); ... } scope.Complete(); } Starting with EF6.0 we have a new way to work with transactions. The new approach is based on Database.BeginTransaction(), Database.Rollback(), Database.Commit(). Yes, no more TransactionScope.
In the followi…

GET call of REST API that contains '/'-slash character in the value of a parameter

Let’s assume that we have the following scenario: I have a public HTTP endpoint and I need to post some content using GET command. One of the parameters contains special characters like “\” and “/”. If the endpoint is an ApiController than you may have problems if you encode the parameter using the http encoder.
using (var httpClient = new HttpClient()) { httpClient.BaseAddress = baseUrl; Task<HttpResponseMessage> response = httpClient.GetAsync(string.Format("api/foo/{0}", "qwert/qwerqwer"))); response.Wait(); response.Result.EnsureSuccessStatusCode(); } One possible solution would be to encode the query parameter using UrlTokenEncode method of HttpServerUtility class and GetBytes method ofUTF8. In this way you would get the array of bytes of the parameter and encode them as a url token.
The following code show to you how you could write the encode and decode methods.