c#删除数组中符合条件的元素(正确写法)

List<int> list = new List<int>() { 1, 2, 3, 4 };
for (int i = 0; i < sz; i++)
    {
        if (i == 1 || i == 2)
            list.RemoveAt(i);
    }

using System.Linq; // Where在Linq里
List<int> list = new List<int>() { 1, 2, 3, 4 };
int sz = list.Count;
list = list.Where((val, idx) => (idx != 1 && idx != 2)).ToList();

            List<int> list = new List<int>() { 1, 2, 3, 4 };
            List<int> list_backup = new List<int>();
            int nIndex = 0;
            int sz = list.Count;
            //list = list.Where((val, idx) => (idx != 1 && idx != 2)).ToList();
            for (int i = 0; i < sz; i++)
            {
                if (i == 1 || i == 2)
                {
                    //list.RemoveAt(i);
                }
                else
                {
                    list_backup.Add(list[i]);
                }
            }
            list = list_backup;

int[] numbers = { 1, 2, 3, 4, 5, 6 };
//移除的元素
int valueToRemove = 5;
//新建一个数组，长度为操作数组的长度-1
int[] newNumbers = new int[numbers.Length - 1];
int index = 0;
for (int i = 0; i < numbers.Length; i++)
{
   if (numbers[i] != valueToRemove)
   {
      newNumbers[index] = numbers[i];
      index++;
   }
}
numbers = newNumbers;
Console.WriteLine(String.Join(",", numbers ));
//结果为：1 2 3 4 6

int[] numbers = { 1, 3, 4, 5, 4, 2 };
//移除的元素
int valueToRemove = 5;
numbers = numbers.Where(val => val != valueToRemove).ToArray()
Console.WriteLine(String.Join(",", numbers));
//结果：1 3 5 2

int[] array = { 1, 3, 4, 5, 4, 2 };
int valueToRemove = 4;
array = Array.FindAll(array, i => i != valueToRemove).ToArray();
Console.WriteLine(String.Join(",", array));
//结果：1 3 5 2

int[] array = { 1, 3, 4, 5, 4, 2 };
int item = 4;
array = array.Except(new int[] { item }).ToArray();
Console.WriteLine(String.Join(",", array));
//结果：1 3 5 2

List<int> numbers = new List<int> {1, 3, 4, 5, 4, 2  };
int valueToRemove = 4;
numbers.RemoveAll(x => x == valueToRemove);
Console.WriteLine(String.Join(",", numbers));
//结果：1 3 5 2

List<int> nums= new List<int> {1, 3, 4, 5, 4, 2  };
int item= 4;
nums.RemoveAt(nums.IndexOf(item));
Console.WriteLine(String.Join(",", nums));
//结果：1 3 5 4 2