由网友(跟着风走把孤独当自由)分享简介：这仅仅是一个好奇的问题，我想知道如果任何人有一个很好的回答：This is just a curiosity question I was wondering if anyone had a good answer to:在.NET Framework类库，我们有例如这两种方法：In the .NET Frame...

这仅仅是一个好奇的问题，我想知道如果任何人有一个很好的回答：

This is just a curiosity question I was wondering if anyone had a good answer to:

在.NET Framework类库，我们有例如这两种方法：

In the .NET Framework Class Library we have for example these two methods:

public static IQueryable<TSource> Where<TSource>(
    this IQueryable<TSource> source,
    Expression<Func<TSource, bool>> predicate
)

public static IEnumerable<TSource> Where<TSource>(
    this IEnumerable<TSource> source,
    Func<TSource, bool> predicate
)

为什么他们使用 Func键＆LT; TSource，布尔＆GT; 而不是 predicate＆LT; TSource＆GT; ？好像 predicate＆LT; TSource＆GT; 仅由名单，其中，T＆GT; 和阵列＆LT; T＆GT; ，而 Func键＆LT; TSource，布尔＆GT; 用于由pretty的多少均可查询和可枚举方法和扩展方法...有什么回事？

Why do they use Func<TSource, bool> instead of Predicate<TSource>? Seems like the Predicate<TSource> is only used by List<T> and Array<T>, while Func<TSource, bool> is used by pretty much all Queryable and Enumerable methods and extension methods... what's up with that?

推荐答案

在 predicate 已经出台，同时该名单，其中; T＆GT; 和阵列＆LT; T＆GT; ，在.NET 2.0中，不同的 Func键和动作变种来自.NET 3.5。

While Predicate has been introduced at the same time that List<T> and Array<T>, in .net 2.0, the different Func and Action variants come from .net 3.5.

因此​​，那些 Func键 predicates主要用于在LINQ运营商的一致性。作为.NET 3.5，关于使用 Func键＆LT; T＆GT; 和动作＆LT; T＆GT; 的guideline国家的：

So those Func predicates are used mainly for consistency in the LINQ operators. As of .net 3.5, about using Func<T> and Action<T> the guideline states:

确实使用了新的LINQ类型 Func键＆LT;＆GT; 和   防爆pression＆LT;＆GT; 而不是定制   代表和predicates

Do use the new LINQ types Func<> and Expression<> instead of custom delegates and predicates