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);
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!

Comments

Popular posts from this blog

Windows Docker Containers can make WIN32 API calls, use COM and ASP.NET WebForms

After the last post , I received two interesting questions related to Docker and Windows. People were interested if we do Win32 API calls from a Docker container and if there is support for COM. WIN32 Support To test calls to WIN32 API, let’s try to populate SYSTEM_INFO class. [StructLayout(LayoutKind.Sequential)] public struct SYSTEM_INFO { public uint dwOemId; public uint dwPageSize; public uint lpMinimumApplicationAddress; public uint lpMaximumApplicationAddress; public uint dwActiveProcessorMask; public uint dwNumberOfProcessors; public uint dwProcessorType; public uint dwAllocationGranularity; public uint dwProcessorLevel; public uint dwProcessorRevision; } ... [DllImport("kernel32")] static extern void GetSystemInfo(ref SYSTEM_INFO pSI); ... SYSTEM_INFO pSI = new SYSTEM_INFO(

Azure AD and AWS Cognito side-by-side

In the last few weeks, I was involved in multiple opportunities on Microsoft Azure and Amazon, where we had to analyse AWS Cognito, Azure AD and other solutions that are available on the market. I decided to consolidate in one post all features and differences that I identified for both of them that we should need to take into account. Take into account that Azure AD is an identity and access management services well integrated with Microsoft stack. In comparison, AWS Cognito is just a user sign-up, sign-in and access control and nothing more. The focus is not on the main features, is more on small things that can make a difference when you want to decide where we want to store and manage our users.  This information might be useful in the future when we need to decide where we want to keep and manage our users.  Feature Azure AD (B2C, B2C) AWS Cognito Access token lifetime Default 1h – the value is configurable 1h – cannot be modified

What to do when you hit the throughput limits of Azure Storage (Blobs)

In this post we will talk about how we can detect when we hit a throughput limit of Azure Storage and what we can do in that moment. Context If we take a look on Scalability Targets of Azure Storage ( https://azure.microsoft.com/en-us/documentation/articles/storage-scalability-targets/ ) we will observe that the limits are prety high. But, based on our business logic we can end up at this limits. If you create a system that is hitted by a high number of device, you can hit easily the total number of requests rate that can be done on a Storage Account. This limits on Azure is 20.000 IOPS (entities or messages per second) where (and this is very important) the size of the request is 1KB. Normally, if you make a load tests where 20.000 clients will hit different blobs storages from the same Azure Storage Account, this limits can be reached. How we can detect this problem? From client, we can detect that this limits was reached based on the HTTP error code that is returned by HTTP