这code返回不同的值。不过，我要的是返回一个强类型集合，而不是匿名类型 [英] This code returns distinct values. However, what I want is to return a strongly typed collection as opposed to an anonymous type

问题描述

我有以下的code：

var foo = (from data in pivotedData.AsEnumerable()
                   select new
                   {
                     Group = data.Field<string>("Group_Number"),
                     Study = data.Field<string>("Study_Name")
                   }).Distinct();

由于预计今年将返回不同的值。不过，我想是返回一个强类型集合，而不是匿名类型，所以当我做的：

As expected this returns distinct values. However, what I want is to return a strongly-typed collection as opposed to an anonymous type, so when I do:

var foo = (from data in pivotedData.AsEnumerable()
                   select new BarObject
                   {
                     Group = data.Field<string>("Group_Number"),
                     Study = data.Field<string>("Study_Name")
                   }).Distinct();

这不返回不同的值，则返回了他们。有没有一种方法与实际对象做到这一点？

This does not return the distinct values, it returns them all. Is there a way to do this with actual objects?

推荐答案

有关鲜明的（）（和许多其他LINQ功能）工作，类被比较（ BarObject 在你的例子）必须实现实施等于（）和 GetHash code（） ，或者提供一个单独的的IEqualityComparer＆LT; T＆GT; 作为参数传递给鲜明的（） 。

For Distinct() (and many other LINQ features) to work, the class being compared (BarObject in your example) must implement implement Equals() and GetHashCode(), or alternatively provide a separate IEqualityComparer<T> as an argument to Distinct().

许多LINQ方法利用 GetHash code（）的性能，因为在内部，他们会使用的东西，像设置＆LT的; T＆GT; 持有独特的项目，它采用了O（1）查找散列。此外， GetHash code（）可以很快告诉你，如果两个对象的可能的是等价的，哪些是绝对不会 - 只要 GetHash code（）正确实施，当然。

Many LINQ methods take advantage of GetHashCode() for performance because internally they will use things like a Set<T> to hold the unique items, which uses hashing for O(1) lookups. Also, GetHashCode() can quickly tell you if two objects may be equivalent and which ones are definitely not - as long as GetHashCode() is properly implemented of course.

所以，你应该让所有的课程你打算在LINQ比较实施等于（）和 GetHash code（）的完整性，或创建一个单独的的IEqualityComparer＆LT; T＆GT; 实施

So you should make all your classes you intend to compare in LINQ implement Equals() and GetHashCode() for completeness, or create a separate IEqualityComparer<T> implementation.

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