C# 检查 list<t> 是否包含任何其他列表
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Check if list<t> contains any of another list
提问by gdp
I have a list of parameters like this:
我有一个这样的参数列表：
public class parameter
{
public string name {get; set;}
public string paramtype {get; set;}
public string source {get; set;}
}
IEnumerable<Parameter> parameters;
And a array of strings i want to check it against.
和我想检查的字符串数组。
string[] myStrings = new string[] { "one", "two"};
I want to iterate over the parameter list and check if the source property is equal to any of the myStrings array. I can do this with nested foreach's but i would like to learn how to do it in a nicer way as i have been playing around with linq and like the extension methods on enumerable like where etc so nested foreachs just feel wrong. Is there a more elegant preferred linq/lambda/delegete way to do this.
我想遍历参数列表并检查源属性是否等于任何 myStrings 数组。我可以用嵌套的 foreach 来做到这一点，但我想学习如何以更好的方式做到这一点，因为我一直在玩 linq 并且喜欢可枚举的扩展方法，比如 where 等，所以嵌套的 foreachs 感觉不对。有没有更优雅的首选 linq/lambda/delegete 方式来做到这一点。
Thanks
谢谢
采纳答案by BrokenGlass
You could use a nested Any()for this check which is available on any Enumerable:
您可以使用嵌套Any()进行此检查，该检查可用于任何Enumerable：
bool hasMatch = myStrings.Any(x => parameters.Any(y => y.source == x));
Faster performing on larger collections would be to project parametersto sourceand then use Intersectwhich internally uses a HashSet<T>so instead of O(n^2) for the first approach (the equivalent of two nested loops) you can do the check in O(n) :
在较大的集合上更快地执行将是投影parameters到source然后使用Intersectwhich 在内部使用HashSet<T>so 而不是 O(n^2) 对于第一种方法（相当于两个嵌套循环），您可以在 O(n) 中进行检查：
bool hasMatch = parameters.Select(x => x.source)
.Intersect(myStrings)
.Any();
Also as a side comment you should capitalize your class names and property names to conform with the C# style guidelines.
另外作为旁注，您应该将类名和属性名大写以符合 C# 样式指南。
回答by Masoud Darvishian
Here is a sample to find if there are match elements in another list
这是一个示例，用于查找另一个列表中是否存在匹配元素
List<int> nums1 = new List<int> { 2, 4, 6, 8, 10 };
List<int> nums2 = new List<int> { 1, 3, 6, 9, 12};
if (nums1.Any(x => nums2.Any(y => y == x)))
{
Console.WriteLine("There are equal elements");
}
else
{
Console.WriteLine("No Match Found!");
}
回答by Umang Agarwal
If both the list are too big and when we use lamda expression then it will take a long time to fetch . Better to use linq in this case to fetch parameters list:
如果两个列表都太大，并且当我们使用 lamda 表达式时，那么 fetch 将需要很长时间。在这种情况下最好使用 linq 来获取参数列表：
var items = (from x in parameters
join y in myStrings on x.Source equals y
select x)
.ToList();
