题目

In this kata you will create a function that takes a list of non-negative integers and strings and returns a new list with the strings filtered out.

Example

ListFilterer.GetIntegersFromList(new List<object>(){1, 2, "a", "b"}) => {1, 2}
ListFilterer.GetIntegersFromList(new List<object>(){1, 2, "a", "b", 0, 15}) => {1, 2, 0, 15}
ListFilterer.GetIntegersFromList(new List<object>(){1, 2, "a", "b", "aasf", "1", "123", 231}) => {1, 2, 231}

代码

using System.Collections;
using System.Collections.Generic;

public class ListFilterer
{
   public static IEnumerable<int> GetIntegersFromList(List<object> listOfItems)
   {
      foreach(var obj in listOfItems){
        if(obj is int){
        yield return (int)obj;
        }
      }
   }
}

参考资料

1. yield：https://docs.microsoft.com/zh-cn/dotnet/csharp/language-reference/keywords/yield
2. is:https://docs.microsoft.com/zh-cn/dotnet/csharp/language-reference/keywords/is