Yes, generics is a good choice. The key to achieving type-safety (and being identify the type with the Type property is to add an abstraction between the list and Field<T> class. Have Field<T> implement the interface IField. This interface doesn’t need any members. Then declare your list as being List<IField>. That way you constrain the … Read more
This wont Clone each item in the list but will create you a new list var new1 = new List<MyObject>(a1); If you want to clone each Item in the list you can implement ICloneable on MyObject var new1 = new List<MyObject>(a1.Select(x => x.Clone())); EDIT: To make it a bit clearer both will copy the elements … Read more
Adding the Required attribute to a list-style property doesn’t really do what you want. The will complain if the list isn’t created, but won’t complain if the list exists with 0 item in it. However, it should be easy enough to derive your own data annotations attribute and make it check the list for Count … Read more
The easiest way to get a new list would be: List<long> unique = longs.Distinct().ToList(); Is that good enough for you, or do you need to mutate the existing list? The latter is significantly more long-winded. Note that Distinct() isn’t guaranteed to preserve the original order, but in the current implementation it will – and that’s … Read more
Give this a try: foreach (PropertyInfo propertyInfo in obj.GetType().GetProperties()) { // do stuff here } Also please note that Type.GetProperties() has an overload which accepts a set of binding flags so you can filter out properties on a different criteria like accessibility level, see MSDN for more details: Type.GetProperties Method (BindingFlags) Last but not least … Read more
(I assume here that Bar and Baz are both subtypes of Foo.) List<? extends Foo> means a list of elements of some type, which is a subtype of Foo, but we don’t know which type. Examples of such lists would be a ArrayList<Foo>, a LinkedList<Bar> and a ArrayList<Baz>. As we don’t know which subtype is … Read more
Type type = pi.PropertyType; if(type.IsGenericType && type.GetGenericTypeDefinition() == typeof(List<>)) { Type itemType = type.GetGenericArguments()[0]; // use this… } More generally, to support any IList<T>, you need to check the interfaces: foreach (Type interfaceType in type.GetInterfaces()) { if (interfaceType.IsGenericType && interfaceType.GetGenericTypeDefinition() == typeof(IList<>)) { Type itemType = type.GetGenericArguments()[0]; // do something… break; } }
I would suggest writing an extension method for this: public static IEnumerable<T> Select<T>(this IDataReader reader, Func<IDataReader, T> projection) { while (reader.Read()) { yield return projection(reader); } } You can then use LINQ’s ToList() method to convert that into a List<T> if you want, like this: using (IDataReader reader = …) { List<Customer> customers = reader.Select(r … Read more
var distinctItems = items.GroupBy(x => x.Id).Select(y => y.First());
Shuffle any (I)List with an extension method based on the Fisher-Yates shuffle: private static Random rng = new Random(); public static void Shuffle<T>(this IList<T> list) { int n = list.Count; while (n > 1) { n–; int k = rng.Next(n + 1); T value = list[k]; list[k] = list[n]; list[n] = value; } } Usage: … Read more