generics

问题 I want to create an interface that works for all the IComparable types. For example public interface SortAlgorithm<T> where T : System.IComparable<T> { List<T> Sort(List<T> input); } And I want its implementors to be generic as well with the same specification I provide in the interface. Like the example below public class InsertionSort<T> : SortAlgorithm<T> Here is my purpose for doing this. I want all my sorting algorithms to work with all types that implements the IComparable interface.

问题 I'm working on making EF easier to unit test by writing some helpers that will make properties for me. I have a couple of backing fields private Mock<DbSet<Workflow>> mockedWorkFlows; private Mock<DbSet<WorkflowError>> mockedWorkFlowErrors; And I want a generic function to be able to return me the correct backing field with the following function public Mock<DbSet<T>> Mocked<T>(T t) where T : class { if ( (object)t is Workflow) { return mockedWorkFlows; //cannot Workflow to T } } There are

问题 I believe that a generic class may make one of its methods available only assuming that its type parameters conform to some additional restrictions, something like (syntax improvised on the spot): trait Col[T] extends Traversable[T] { def sum[T<:Int] :T = (0/:this)(_+_) } I guess I could use implicit parameters as evidence... Is there a language feature for this? 回答1: In this case you can only use an implicit parameter, as the type gets determined before the method call. trait Col[T] extends

问题 How to convert List<int> to List<long> in C#? 回答1: Like this: List<long> longs = ints.ConvertAll(i => (long)i); This uses C# 3.0 lambda expressions; if you're using C# 2.0 in VS 2005, you'll need to write List<long> longs = ints.ConvertAll<int, long>( delegate(int i) { return (long)i; } ); 回答2: List<int> ints = new List<int>(); List<long> longs = ints.Select(i => (long)i).ToList(); 回答3: var longs = ints.Cast<long>().ToList(); 来源： https://stackoverflow.com/questions/3295957/convert-listint-to

问题 How to convert List<int> to List<long> in C#? 回答1: Like this: List<long> longs = ints.ConvertAll(i => (long)i); This uses C# 3.0 lambda expressions; if you're using C# 2.0 in VS 2005, you'll need to write List<long> longs = ints.ConvertAll<int, long>( delegate(int i) { return (long)i; } ); 回答2: List<int> ints = new List<int>(); List<long> longs = ints.Select(i => (long)i).ToList(); 回答3: var longs = ints.Cast<long>().ToList(); 来源： https://stackoverflow.com/questions/3295957/convert-listint-to

问题 I am trying to understand bounded types and not quite grasping the point of them. There is an example of bounded generics on which provides this use case: public class NaturalNumber<T extends Integer> { private T n; public NaturalNumber(T n) { this.n = n; } public boolean isEven() { return n.intValue() % 2 == 0; } // ... } If you are going to restrict the classes that can be the parameterized type, why not just forget the parameterization all together and have: public class NaturalNumber {

问题 I am trying to understand bounded types and not quite grasping the point of them. There is an example of bounded generics on which provides this use case: public class NaturalNumber<T extends Integer> { private T n; public NaturalNumber(T n) { this.n = n; } public boolean isEven() { return n.intValue() % 2 == 0; } // ... } If you are going to restrict the classes that can be the parameterized type, why not just forget the parameterization all together and have: public class NaturalNumber {

问题 public K[] toArray() { K[] result = (K[])new Object[this.size()]; int index = 0; for(K k : this) result[index++] = k; return result; } This code does not seem to work, it will throw out an exception: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to ... Could someone tell me how I can create an array with a generic type? Thanks. 回答1: You can't: you must pass the class as an argument: public <K> K[] toArray(Class<K> clazz) { K[] result = (K[])Array.newInstance(clazz,this.size

问题 public K[] toArray() { K[] result = (K[])new Object[this.size()]; int index = 0; for(K k : this) result[index++] = k; return result; } This code does not seem to work, it will throw out an exception: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to ... Could someone tell me how I can create an array with a generic type? Thanks. 回答1: You can't: you must pass the class as an argument: public <K> K[] toArray(Class<K> clazz) { K[] result = (K[])Array.newInstance(clazz,this.size

问题 public K[] toArray() { K[] result = (K[])new Object[this.size()]; int index = 0; for(K k : this) result[index++] = k; return result; } This code does not seem to work, it will throw out an exception: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to ... Could someone tell me how I can create an array with a generic type? Thanks. 回答1: You can't: you must pass the class as an argument: public <K> K[] toArray(Class<K> clazz) { K[] result = (K[])Array.newInstance(clazz,this.size