C＃linq从字典中选择

Question

How to get part of dictionary, which keys are true for some conditionals. For example, I have a dictionary.

var dictionary = new Dictionary<string, int>();
dictionary["first"] = 1;
dictionary["firstOfSecond"] = 2;
dictionary["second"] = 3;
dictionary["first-and-second"] = 4;

I need part of this dictionary, which keys are started from "first". How to do it?

Answer 1

var result = dictionary.Where(x => x.Key.Contains("first"));

要么

var result = dictionary.Where(x => x.Key.StartsWith("first"));

Answer 2

var result = dictionary.Where(x => x.Key.StartsWith("first", StringComparison.OrdinalIgnoreCase));

所有以first开头的键，但不包括任何大小写。

Answer 3

You can use StartWith method of string:

var result= dictionary.Where(x => x.Key.StartWith("first"));

StartWith has an overload where you can pass the StringComparison you want to use, eg, the current culture or the invariant culture, word or ordinal sort rules, and be case-sensitive or case-insensitive.

Answer 4

dictionary.Keys.Where（t => t.StartsWith（“ first”））。ToList（）;