int IDuser = 100;
           int[] IDUserkey = { 94, 96, 98, 100 };

           if (! IDUserkey.Contains(IDuser))
           {
               // ID User is not present
               // your code here..... 
           }
           else
           {
               // ID User is present
           }

注意：使用系统添加此命名空间

using System.Linq;

Cheeck

Cheeck

bool result = IDUserkey.Contains( IDuser);

如果您知道数组已排序，您可以使用：



bool exists = Array.BinarySearch（ array_1，variable_1）> = 0;

那将是O（log n）ra比O（n）（所有其他都是），但它确实需要先排序数组。



就我个人而言，我通常选择第一种形式 - 假设您使用的是.NET 3.5或更高版本。



如果您需要检查多个项目并且数组很大，您可能需要创建一个HashSet< int>



HashSet< int> hashSet = new HashSet< int>（array_1）;

bool exists = hashSet.Contains（variable_1）

If you know that the array is sorted, you can use:

bool exists = Array.BinarySearch(array_1, variable_1) >= 0;
That will be O(log n) rather than O(n) (which all the others are), but it does require the array to be sorted first.

Personally I normally go with the very first form - assuming you are using .NET 3.5 or higher.

If you need to check for several items and the array is large, you may want to create a HashSet <int>

HashSet <int> hashSet = new HashSet <int>(array_1);
bool exists = hashSet.Contains(variable_1)