Where we should add ServiceKnownType in WCF?

Sujeet Suman

10y4.5k

What is the good practice to write ServiceKnownType In WCF.

Either with the interface or with the method?

7 Replies

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Ramesh Kartik10y ago
Accepted answer
Hello Sujeet,

Service Contract level is the right choice for your requirement as your service has more than 50 methods. This is no where related to any performance issue, infact knowntype keyword conveys the class relationship to the DataContractSerializer to deserialize the content. You can go-ahead with this approach

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Ramesh Kartik10y ago
Hello Sujeet,

In the place of parent type if you are returning child type from service then you must use Knowntype which will never degrade your service performance
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Sujeet Suman10y ago
Hi Ramesh again thanks for your reply.
Can you pls clear my one more doubt.
Is adding known type at service level will attached those all known type with all methods. Is in this way many unwanted known type will added with many method. And that will degrade service performance.

Is there something like that ?????
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Sujeet Suman10y ago
Thank you so much Ramesh.
You answer is really worthy. But I am having some doubt.

(01.)When need to add known type at method level, then we should add at OperationContract level.

(02.)When need to add known type at service level, then we should add at ServiceContract level.

(03.) If need for many service contract, then add at DataContract level.

Suppose in my service there are more than 50 methods & many user defined type repeatedly need to write on many operation contract.

So suppose I am writing globally, then is this degrade my service performance.?????
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Ramesh Kartik10y ago
Hello Sujeet,

KnownType should be used when the type of data is not known during the client service communication in WCF.In most scenarios, like the data the service is sending back to the client is not the actual data of the contract but a derived type of it. In that case you need to go for a Known type.

Sujeet, Its not about a good practice to write ServiceKnownType in WCF,its about going with a interface or method level is based upon your requirement. If you want your type should be globally known to all the service contracts,operation contracts then go for a DataContract Level, If you want your type should be known to a particular service,then go for a Service Contract Level, If you want your type should be known to a particular method then for a Operation Contract Level. According to your requirements you can decide it by own.

Do you think am confusing me? Please read this article,
http://www.c-sharpcorner.com/UploadFile/rkartikcsharp/knowntypes-of-data-contract-in-wcf/
If am answered your question,please mark it as "ACCEPTED ANSWER"
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Sujeet Suman10y ago
Thanks Prakash for reply.

But I am asking about best practice.
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Prakash Kumar10y ago
Interface
[ServiceKnownType("GetKnownTypes", typeof(Helper))]
[ServiceContract()]
public interface ICatalog
{
    // Any object type can be inserted into a Hashtable. The
    // ServiceKnownTypeAttribute allows you to include those types
    // with the client code.
    [OperationContract]
    Hashtable GetItems();
}
refer the below link,
https://msdn.microsoft.com/en-us/library/system.servicemodel.serviceknowntypeattribute(v=vs.110).aspx
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