I write a WCF service for Insert and delete operation here we used generic method but it gives following error
"System.Runtime.Serialization.InvalidDataContractException: Type 'T' cannot be exported as a schema type because it is an open generic type. You can only export a generic type if all its generic parameter types are actual types."
here "EntityBase2" is base class for all entities
[ServiceContract]
[ServiceKnownType(typeof(EntityBase2))]
public interface IBackupUtility
{
[OperationContract]
void Delete<T>(T entity) where T : EntityBase2;
[OperationContract]
void InsertORUpdate<T>(T entity) where T : EntityBase2;
}
Question is how i can expose generic type 'T'?
I think it is imposible, how could it generate the wsdl that way?
You have two options:
You could send the type as a parameter.
If you want to expose crud operations for entities I would recommend to use a code generator, maybe a T4 template for EF.
This post is old indeed, but maybe someone find this solution useful:
WCF and Generics
Answer to this question is both Yes and No. Yes for server prospective and No for client prospective.
We can create a generic Data Contract on server but while using that in any operation contract we have to specify a data type of the generic.
And at client end that data contract will be exposed only as a strongly data type not generic.
[DataContract]
public class MyGenericObject<T>
{
private T _id;
[DataMember]
public T ID
{
get { return _id; }
set { _id = value; }
}
}
[OperationContract]
MyGenericObject<int> GetGenericObject();
This is what we have in Server we can see while using generic data contract we have to specify the type otherwise it’ll give compile time error.
On client what we get from WSDL is a follow:
[DataContract]
public class MyGenericObjectOfint
We can see here what we get from WSDL is not a generic data contract WSDL proxy generate a class with a new name using some convention.
Convention used is
Generic Class Name + "Of" + Type Parameter Name + Hash
Hash is not always generated, it’ll be generated only when there is a chance of name collision.
Related
I have a ServiceContract which returns dynamic type and looks like following:
public dynamic LoginViaOpenId(string openIdUrl)
The dynamic return type could be a DataContract that I have defined, or a string. But since I have not used my DataContract on the service, client does not know anything about it and cannot access it.
My DataContract is something like below:
[DataContract]
public enum OpenIdStatus
{
[EnumMember]
Authenticated,
[EnumMember]
Authenticating,
[EnumMember]
Cancelled,
[EnumMember]
Failed,
[EnumMember]
RedirectToLogon
}
I know if I had hierarchical types I could have used KnownType to conquer this, but am out of idea for this scenario.
Any idea?
A dynamic DataContract is an oxymoron. A DataContract is a predetermined and mutually agreed-upon data structure, and dynamic is an object whose structure is not predetermined and thus cannot be agreed-upon, since it can be anything.
It doesn’t appear you actually need to return a dynamic data type, but rather a varying data type. The difference is that a varying data type is one of a set of fixed data types, whereas a dynamic data type is one which does not have a predetermined structure. Since your return value is one of several knows shapes, there is no need to use the "shapeless" (or "freeform") dynamic type, which isn't supported by WCF.
Instead, you could have the [OperationContract] method return a type with a [DataContract] that will act as a wrapper object that has a single data member of type object, and use [KnownType] on the wrapper object to specify the possible types that may be returned inside the wrapper. Since everything inherits from object, there is already a hierarchy in place.
[DataContract]
[KnownType(typeof(OpenIdStatus))]
[KnownType(typeof(string))]
public class ReturnValue
{
[DataMember]
public object Value { get; set; }
}
I think that WCF is going to have issues serializing / deserializing your dynamic type. I would recommend that you set up a contract for the method return based on a defined interface. Alternatively, you could take responsibility for the serialization yourself and make your service return a string. The client will have to have knowledge of what type to de-serialize the string to. There is a similar question on this here:-
How to return dynamic List from WCF HTTP Service
I am trying to use WCF service to upload GZip files. Im trying to compress files using Gzip and then passing it through to WCF service to be uploaded to server.
Every time I'm running the code I get this error message
'System.IO.Compression.GZipStream' cannot be serialized. Consider
marking it with the DataContractAttribute attribute, and marking all
of its members you want serialized with the DataMemberAttribute
attribute.
I have marked this property member to be [DataMember]. I have also done the [DataContract] and below that added [Serialiable] which is not needed to be honest.
Can any one help?
I am not too sure this is a proper way, but it worked for me.
1) Create a Data Transfer Object class
[DataContract]
class ZippedDataDTO
{
[DataMember]
public byte[] RawData {get;set;}
//other relevant metadata
}
2) Once data is compressed, get bytes from the stream, smth like .ToArray()
3) Assign the zipped raw bytes to DTO's RawBytes
4) Return this DTO as a part of your WCF service contract
[ServiceContract]
interface IService
{
[OperationContract]
ZippedDataDTO GetZippedData();
...
}
[DataContract()]
public class Contract
{
.........
Some Properties with DataMembers Attribute.
............
..............
[DataMember(Name = "FirstName")]
public string Name { get; set; }
}
I have above class and I have two web methods (operations)
In 1st web method I want to expose Name as FirstName and in 2nd web method expose Name as LastName.
I don't want to create separate data contracts.
Please tell me how to achieve this?
You can use reflection and change the value of the attribute at runtime depending on which method you in currently. Check out these links on StackOverflow:
How to set attributes values using reflection
Change Attribute's parameter at runtime
But I think the best way would be to either have 2 separate contracts or create a contract with both properties.
You can also implement a surrogate to special-case this type during serialization. As an example, see the Data Contract Surrogate sample.
I've got several data contract classes like this:
[DataContract]
public class FooData
{
[DataMember]
public string Name;
// ... many more members
public FooData (string name) // again, many more arguments
{
Name = name;
// ...
}
}
Since FooData is always used to transport Foo objects over the wire, I'd like to add an constructor that takes a Foo object and sets all fields accordingly instead of doing it manually (new FooData (myFoo.Name)).
However, this would require the user of FooData to include the Foo type, which is supposed to be internal to the server. Ordinarily, this issue would be solved by making the constructor taking the Foo internal, but in my case FooData is in a different assembly than Foo.
How should I deal with this? My thoughts so far include using an interface instead of a class to transport data as well, or using an "extension constructor". Any better ideas?
Including the Foo type on the constructor should not be a problem as long as you don't expose that type in a public property marked with DataMember. WCF will take care of serializing only the properties marked with DataMember, so you can internally use your server types in the data contract. However, the client will not able to see that constructor that receives the "Foo" type, so it will have to set all the data in the contract manually
Thanks
Pablo.
Hey, I can't seem to access the returned value from a method I called on my Host.
//Service---------------------------------------------------------
[DataMember]
private List<CalculationRecord> History = new List<CalculationRecord>();
public IEnumerable<CalculationRecord> CalculationHistory()
{
return (IEnumerable<CalculationRecord>)History;
}
public CalculationResult Calculate(CalculationNode problem)
{
CalculationResult calcResult = new CalculationResult();
//Calculates results of expression
CalculationEvaluation Evaluator = new CalculationEvaluation();
Evaluator.Calculate(problem, calcResult);
return calcResult;
}
//interface---------------------------------------------------------
[ServiceContract]
public interface ICalculate
{
[OperationContract]
CalculationResult Calculate(CalculationNode problem);
[OperationContract]
IEnumerable<CalculationRecord> CalculationHistory();
}
//Client------------------------------------------------------------
CalculatorClient client = new CalculatorClient();
ICalculate calcProxy = client.ChannelFactory.CreateChannel();
CalculationNode calcRootNode = parser.Parse(expression);
CalculationResult result = calcProxy.Calculate(calcRootNode);//result is null
You're under a wrong impression - the DataContract that the server exposes can (and should) only contain data - never any behavior. As such, you can never share an object between client and host - all you can share are service methods to call, and concrete types to use on those methods. That's it.
The process is this: when the client connects up to the server, it will download the metadata for the service - it can find out what service methods are available, what data those take - but it cannot infer any additional methods on the data contract. It just can't. The client then builds up an exact copy of the data contract type - but it's a totally separate class, and it only matches the server-side data contract class as far as its serialized representation in XML is concerned. It is not the same class - it just look the same.
Because in the end, all that happens between the server and the client is an exchange of a serialized message - basically a XML text document. You are not sending across a .NET object! All you're exchanging is a data representation of your data contract, nothing more.
So in your case, the client side proxy will have a new class that looks like the one the server uses - at least on the serialized level on the wire - but it will not contain the Calculate method. The Calculate method you're calling is on the service contract - it's not the one on the data member you have.
In your concrete example, too - you seem to be intermixing [DataMember] and service interface definition. Avoid this at all costs. Also, all the types involved in the calculation - most definitely CalculationNode and CalculationResult - must be exposed as [DataContract] elements containing a number of [DataMember] fields or properties. This is not clear from the snippet of code you posted.