转换IEnumberable＆LT; T＆GT;列出＆LT; T＆GT;在LINQ的结果，巨大的性能损失 [英] Converting IEnumberable<T> to List<T> on a LINQ result, huge performance loss

问题描述

在一个LINQ的结果，你喜欢这样的：

On a LINQ-result you like this:

var result = from x in Items select x;
List<T> list = result.ToList<T>();

不过，了ToList＆LT; T＆GT; 实在是太慢了，它榜上无名可变的，因此，转换速度慢？

However, the ToList<T> is Really Slow, does it make the list mutable and therefore the conversion is slow?

在大多数情况下，我能设法只是我的的IEnumerable 或 Paralell.DistinctQuery ，但现在我想项目绑定到一个DataGridView，所以因此我需要的不是的IEnumerable ，建议我如何将获得的了ToList或更换性能？

In most cases I can manage to just have my IEnumerable or as Paralell.DistinctQuery but now I want to bind the items to a DataGridView, so therefore I need to as something else than IEnumerable, suggestions on how I will gain performance on ToList or any replacement?

在10畅想记录在的IEnumerable 的 .ToList＆LT; T＆GT; 需要6秒左右。

On 10 milion records in the IEnumerable, the .ToList<T> takes about 6 seconds..

推荐答案

.ToList（）是比较慢的什么的？

如果你是比较

var result = from x in Items select x;
List<T> list = result.ToList<T>();

到

var result = from x in Items select x;

您应该注意，由于查询被懒洋洋地评估，第一行并没有做很多的。它不检索任何记录。 延迟执行的使这种比较的完全不公平的的。

you should note that since the query is evaluated lazily, the first line doesn't do much at all. It doesn't retrieve any records. Deferred execution makes this comparison completely unfair.

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