将类中的字符串添加到List中的简便方法 <string> ？

Question

I have the following C# code:

List<string> names = new List<string>();
if (myObject.myClass != null)
{
     foreach (var foo in myObject.myClass.subClass)
     {
          names.Add(foo.Name);
     }
}

Is there a shorter way of writing this without the need to iterate through each instance of subClass to add myObject.myClass.subClass.Name into the names List<string> object?

Also baring in mind myObject.myClass can be null.

Answer 1

It sounds like you could use:

List<string> names = myObject.myClass == null
    ? new List<string>()
    : myObject.myClass.subclass.Select(x => x.Name).ToList();

Note that this expression: myObject.myClass.subclass suggests you're violating the Law of Demeter fairly nastily - and I hope the naming doesn't actually reflect reality though... if you could provide a more indicative set of expressions, that would help a lot.

Answer 2

You can use the AddRange method to add all elements of an IEnumerable to a list:

if (myObject.myClass != null) {
    names.AddRange(myObject.myClass.subClass.Select(c => c.Name));
}

Answer 3

您可以在List上使用AddRange方法。

Answer 4

您可以使用LINQ来构建列表，但请注意，它仍然是枚举以构建列表：

var names = myObject.myClass.subClass.Select(x => x.Name).ToList();

Answer 5

It's not clear what is a collection and what is not. So i assume that myObject.myClass is already a collection( IEnumerable<myClass> ) and can be null and myClass.subClass is an IEnumerable<subClass> and you want all of their names.

var classNames = from c in myObject.myClass
                 where c != null
                 from subC in c.subClass
                 where subC != null
                 select subC.Name;
List<String> names = classNames.ToList();

This is a LINQ query, it's the equivalent of Enumerable.SelectMany in method syntax.

Note that you need to add using System.Linq .