C# 我们在 IEnumerable 中有“包含”方法吗
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Do we have a "Contains" method in IEnumerable
提问by Bohn
I have a class in my code that is already deriving from IEnumerable. I was wondering if there is a way that I can use a "Contains" method on its instnaces to look for a something in that list?
我的代码中有一个类已经从 IEnumerable 派生。我想知道是否有一种方法可以在其实例上使用“包含”方法来查找该列表中的某些内容？
采纳答案by Jon Skeet
Do you reallyimplement the non-generic IEnumerable, or the generic IEnumerable<T>? If you can possibly implement the generic one, your life will become a lot simpler - as then you can use LINQ to Objects, which does indeed have a Containsextension method.
你真的实现了非泛型IEnumerable，还是泛型IEnumerable<T>？如果你可以实现通用的，你的生活就会变得简单得多——因为这样你就可以使用LINQ to Objects，它确实有一个Contains扩展方法。
Otherwise, you could potentially convert from the non-generic to generic using Castor OfType, e.g.
否则，您可能会使用Castor将非泛型转换为泛型OfType，例如
bool found = nonGeneric.Cast<TargetType>().Contains(targetItem);
It would be nicer if you just implemented the generic interface to start with though :)
如果您只是实现了通用接口，那就更好了:)
回答by Darin Dimitrov
No, there's no such method in the IEnumerable<T>interface. There's an extension methodthough that you could use.
不，IEnumerable<T>界面中没有这样的方法。有一个extension method虽然你可以使用。
using System.Linq;
and then:
进而：
IEnumerable<string> foos = new[] { "foo", "bar", "baz" };
bool IsThereABar = foos.Contains("bar");
回答by Smagin Alexey
public static bool Contains<T>(this IEnumerable source, T value)
{
foreach (var i in source)
{
if (Equals(i, value))
return true;
}
return false;
}
If you want, you can add custom comparer as parameter ti extension method Contains
如果需要，您可以添加自定义比较器作为参数 ti 扩展方法包含
