WCF - Error handling in service layer

Hi,

I am working on a WCF service and working on a exception handling.
I'd like to know the best practice for returning exception.

Option 1 :  use request/response pattern

public ServiceResponse MethodTest(ServiceRequest)
{
}

Class ServiceResponse
{
        ResponseObject;
        FaultException;
        ValidationError;
}

1. If there is any exception than faultexception object will contain the error and remaining 2 object will be null
2. If there is Business rule failure than ValidationError will have all the error and remaining 2 objects will be null
3. If it is sucess responseobject will contain the data

Option 2 : returning faultexception

public ResponseObject MethodTest(string)
{
}

1. If there is any exception than throw faultexception with error
2. If there is Business rule failure than throw faultexception with validationerror
3. If it is sucess return responseobject will contain the data


I am not able to decide between this 2 options, which option should I use , please suggest.

Thanks,
Y KAsked:
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Vel EousResearch & Development ManagerCommented:
I would be more inclined to use your second option, for example:

public ResponseObject DoSomething(int x)
{
    var responseObject = new ResponseObject();
    try
    {
        // do some work
        responseObject.Property = "FooBar";
        // test some buisiness logic
        if (!Equals(x, 1)) // fail
        {
            throw new FaultException("Failed business rule.");
        }
    }
    catch (FaultException ex)
    {
        throw;
    }
    catch
    {
        throw new FaultException("Something went horribly wrong!");
    }
    return responseObject;
}

public class ResponseObject
{
    public string Property { get; set; }
}

try
{
    var ret = this.DoSomething(2);
}
catch (Exception ex)
{
    Debug.WriteLine(ex.Message);
}

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Y KAuthor Commented:
Hi Tchuki,

Thanks for your quick response.

Can you please let me know below

1. What is the benefits of using 2nd option.
2. how can I use to send multiple business rule validation error at once.

Thanks,
0
Vel EousResearch & Development ManagerCommented:
My preference for the second option is that it feels more natural and standard than the first option, either your client gets an object in response (all is good) or an exception (something went wrong).

If you want to pass additional useful information over the wire aside from just a simple string (as per my previous example), you can make use of FaultException<TDetail>.

An example extending the previous to use FaultException<T>:

public ResponseObject DoSomething(int x)
{
    var responseObject = new ResponseObject();
    try
    {
        // do some work
        responseObject.Property = "FooBar";
        // test some buisiness logic
        if (!Equals(x, 1)) // fail
        {
            var error = new BusinessValidationError()
            {
                Message = "Failed business rule(s).",
                ValidationErrors = new List<string> { "Failed bussines rule A", "Failed business rule B"}
            };
            throw new FaultException<BusinessValidationError>(error);
        }
    }
    catch (FaultException ex)
    {
        throw;
    }
    catch
    {
        throw new FaultException("Something went horribly wrong!");
    }
    return responseObject;
}

public class ResponseObject
{
    public string Property { get; set; }
}

[DataContract]
public class BusinessValidationError
{
    [DataMember]
    public string Message { get; set; }
    [DataMember]
    public List<string> ValidationErrors { get; set; }
}

[ServiceContract]
public interface IBusinessService
{
    [OperationContract]
    [FaultContract(typeof (BusinessValidationError))]
    ResponseObject DoSomething(int x);
}

try
{
    var ret = this.DoSomething(2);
}
catch (FaultException<BusinessValidationError> ex)
{
    Debug.WriteLine(ex.Detail.Message);
    ex.Detail.ValidationErrors.ForEach(Debug.WriteLine);
}
catch (Exception ex)
{
    Debug.WriteLine(ex.Message);
}

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