If one calls the .Max() extension method on an IEnumerable<T>, and the objects within do not implement IComparable, one gets System.ArgumentException: At least one object must implement IComparable. Why don't Max and similar methods constrain T to implement IComparable, so that this problem can be caught at compile time instead of at ru...
bool IsTypeAGenericList(Type listType) { typeof(IList<>).IsAssignableFrom(listType.GetGenericTypeDefinition()) } returns false when given typeof(List<int>). I assume this is because the two type parameters can be different, correct? ...
Why can I do this: public T GetMainContentItem<T>(string moduleKey, string itemKey) { return (T)GetMainContentItem(moduleKey, itemKey); } but not this: public T GetMainContentItem<T>(string moduleKey, string itemKey) { return GetMainContentItem(moduleKey, itemKey) as T; } It complains that I haven't restricted the generic t...
I have an interface interface x { A getValue(); } and the implementation class y implements x { public B getValue() { return new B();} } B is a subclass of A. This works because of covariant overriding, I guess. But if I rewrite the interface as interface x{ <T extends A> T getValue(); } I get a warning in the i...
Duplicate In C#, why can’t a List object be stored in a List variable Here is my code: public class Base { protected BindingList<SampleBase> m_samples; public Base() { } } public class Derived : Base { public Derived() { m_samples = new BindingList<SampleDerived>();...
Possible Duplicate: Is there a Set data structure in .Net? Duplicate: this is a duplicate of "Is there a “Set” data structure in .Net?". Please close it as a duplicate and address any further answers to the earlier question. Is there a generic collection analogous to the STL set<T> template in the .NET framework? If not, how w...
How do Concepts (ie those recently dropped from the C++0x standard) differ from Interfaces in languages such as Java? ...
Suppose I have two classes, Input and Output, which are designed to be connected to each other. Output produces values of some type, and Input consumes them. class Input[T] { var output: Option[Output[_ <: T]] = None } class Output[T] { var input: Option[Input[_ >: T]] = None } It's okay if an Input and Output pair don't operate o...
I would like to be able to detirmine the return type of my method call at runtime, but I can not seem to be able to get the Type of T. public <T> T getT() { Object t = null; Class<?> c = t.getClass(); System.out.println(c.getName()); return (T) t; } Is there any way to determine the Type of T at runtime in Java? ...
I have a collection class with an Equals method that I want to pass in a method to do equality checking between each item. Furthermore, I want to allow the delegate type to operate on superclasses of T as well as T itself: public delegate bool EqualityComparer<T>(T x, T y); public class Collection<T> { //... public bool Equals...
Hi I want to create my custom collection, I am deriving my custom collection class from CollectionBase class as below: public class MyCollection : System.Collectio.CollectionBase { MyCollection(){} public void Add(MyClass item) { this.List.Add(item); } } class MyClass { public string name; } Let me ask a f...
Which type cannot be used as generics? ...
This question got me thinking on how one could approach writing a method that would need to contain a variable list of type parameters. One approach would be to accept params Type[] as part of the arguments, such as: public static bool IsOneOf(this object obj, params Type[] types) { return types.Contains(obj.GetType()); } Howeve...
Hello, I have a generic method public static void DoSomething<T>() {...} . Now I want to restrict that T. public static void DoSomething<T>() where T: IInterface1 {...} But what I really want is allowing multiple interfaces, something like public static void DoSomething<T>() where T: IInterface1, IInterface2 {...} But that does...
I have a class Foo with subclass SubFoo, a collection class FooListing. I want to create a generic FooListing<T> where T is either Foo or a subclass of Foo From the wording of the documentation (under 'Wildcards'), it sounds like public class FooListing<T extends Foo> { ... } ...would let me use FooListing<SubFoo>, but not FooListin...
Hello good people! in my long journey to learn about hibernate, i wanted to use generic DAO and came across a good article at the hibernate site and tried out the IMPLEMENTATION WITH HIBERNATE Section.I'm having an error saying :GenericDAOImpl.java:[22,16] name clash: makeTransient(T) in GenericDAOImpl and makeTransient(T) in GenericDAO ...
I am trying to derive the type of an object at runtime. Specifically I need to know two things whether it implements ICollection or IDto. Currently my only solution I have been able to find is this: private static bool IsACollection(PropertyDescriptor descriptor) { bool isCollection = false; foreach (Type type ...
What I want to do is, based on the type of T do different opperations. Below is a simple example of my problem. Public Shared Function Example(Of T)() As T Dim retval As T If TypeOf retval Is String Then Dim myString As String = "Hello" retval = myString ElseIf TypeOf retval Is Integer Then Dim myInt...
When building my application in release mode, I get an internal error URW1135 at the end of one of my files. I searched the internet and found (here) that it could be about arrays of generic types like MyClass <T> = class FArray : array of T; end; So, I applied the proposed workaround (declaring a type TArrayType = array of T) throu...
I have problems to get generics to work in the following scenario: Delphi provides the interface IComparable: IComparable <T> = interface function CompareTo (Value : T) : Integer; end; I add another interface IPersistent: IPersistent = interface function ToString : String; procedure FromString (const Str : String); end; One...