C# Linq Where(expression).FirstorDefault() vs .FirstOrDefault(expression) [英] C# Linq Where(expression).FirstorDefault() vs .FirstOrDefault(expression)

问题描述

这两个 Linq 查询有什么区别:

What is the difference between these two Linq queries:

var result = ResultLists().Where( c=> c.code == "abc").FirstOrDefault();
// vs.
var result = ResultLists().FirstOrDefault( c => c.code == "abc");

• 语义是否完全相同?
• 如果语义相等，FirstOrDefault 的谓词形式比 Where() 加上普通的 FirstOrDefault() 提供任何理论或实际性能优势?
• Are the semantics exactly the same?
• Iff sematically equal, does the predicate form of FirstOrDefault offer any theoretical or practical performance benefit over Where() plus plain FirstOrDefault()?

推荐答案

哪个都行.

它们都懒惰地运行 - 如果源列表有 100 万个项目，但第 10 个项目匹配，那么它们都只会从源中迭代 10 个项目.

They both run lazily - if the source list has a million items, but the tenth item matches then both will only iterate 10 items from the source.

性能应该几乎相同，任何差异都将完全无关紧要.

Performance should be almost identical and any difference would be totally insignificant.

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