преобразуйте список объектов от одного типа до другого лямбда-выражения использования
У меня есть цикл foreach, читая список объектов одного типа и производя список объектов другого типа. Мне сказали, что лямбда-выражение может достигнуть того же результата.
var origList = List<OrigType>(); // assume populated
var targetList = List<TargetType>();
foreach(OrigType a in origList) {
targetList.Add(new TargetType() {SomeValue = a.SomeValue});
}
Любая справка ценилась бы - я плохо знаком с лямбдой и linq спасибо, s
5 ответов
Try the following
var targetList = origList
.Select(x => new TargetType() { SomeValue = x.SomeValue })
.ToList();
This is using a combination of Lambdas and LINQ to achieve the solution. The Select function is a projection style method which will apply the passed in delegate (or lambda in this case) to every value in the original collection. The result will be returned in a new IEnumerable. The .ToList call is an extension method which will convert this IEnumerable into a List.
I believe something like this should work:
origList.Select(a => new TargetType() { SomeValue = a.SomeValue});
If you know you want to convert from List to List then List will be slightly more efficient than Select/ToList because it knows the exact size to start with:
target = orig.ConvertAll(x => new TargetType { SomeValue = x.SomeValue });
In the more general case when you only know about the source as an IEnumerable, using Select/ToList is the way to go. You could also argue that in a world with LINQ, it's more idiomatic to start with... but it's worth at least being aware of the ConvertAll option.
Вот простой пример ..
List<char> c = new List<char>() { 'A', 'B', 'C' };
List<string> s = c.Select(x => x.ToString()).ToList();
var list1 = new List<Type1>();
var list2 = new List<Type2>();
list1.ForEach(item => list2.Add(new Type2() { Prop1 = value1 }));