Question

I am trying to create a function like

        public static TResponse Run<TService, TResponse>(Controller mvcController,            IServiceController serviceController, Func<TService, TResponse> action, bool suppressErrors)
        where TService : ICommunicationObject
        where TResponse : ResponseBase<TResponse>
    {
        TResponse response = serviceController.Run<TService, TResponse>(action);
        if (!suppressErrors)
            response.Result.Errors.ToList().ForEach(i => mvcController.ModelState.AddModelError(UniqueKey.ValidationMessage, i.Message));
        return response;
    }

and class has been defined as

[DataContract]
public class ResponseBase<T> where T: new()
{
    public ResponseBase()
    {
        Result = new Result<T>();
    }

    [DataMember]
    public Result<T> Result { get; set; }
}

I am getting the compilation error as TResponse must be a non abstract type with a parameterless constructor in order to use it as parameter TResponse

Any help would be appreciated..

Answer 1

Although you’ve defined the new() constraint for T in ResponseBase<T>, the compiler requires you to declare the same constraint in other classes that use ResponseBase<T> generically.

All you have to do is add the new() constraint to TResponse in your method:

public static TResponse Run<TService, TResponse>(Controller mvcController, IServiceController serviceController, Func<TService, TResponse> action, bool suppressErrors)
    where TService : ICommunicationObject
    where TResponse : ResponseBase<TResponse>, new()