[英]Using Linq Select to create a list that contains more items than the original list
I have a list of items.我有一个项目清单。 For example (although the list could be any length):例如(尽管列表可以是任意长度):
var inputList = new List<Input1>()
{
new Input1() { Test = "a" },
new Input1() { Test = "b" }
};
What I want to do is create a new list of:我想要做的是创建一个新列表:
a1, a2, b8, b9
That is the value of Test
(ie a) with a suffix based on the value of Test
.那是Test
的值(即 a),其后缀基于Test
的值。
In that order.以该顺序。 Obviously, this is a minimum workable example, not the actual problem.显然,这是一个最小的可行示例,而不是实际问题。 So I'd like to use something like the .Select
to split the data - something like this:所以我想使用类似.Select
的东西来分割数据 - 像这样:
var outputList = inputList.Select(x =>
{
if (x.Test == "a")
{
return new Input1() { Test = "a1" };
//return new Input1() { Test = "a2" };
}
else if (x.Test == "b")
{
return new Input1() { Test = "b8" };
//return new Input1() { Test = "b9" };
}
else
{
return x;
}
});
Input1
for completeness: Input1
完整性:
class Input1
{
public string Test { get; set; }
}
That is, to return a list that contains items that were not in the original list.也就是说,返回一个列表,其中包含不在原始列表中的项目。
I realise I can use a foreach
, but I'm interested if there's a better / more concise way.我意识到我可以使用foreach
,但如果有更好/更简洁的方法,我很感兴趣。
Suppose you have a method that transforms your single input into multiple inputs:假设您有一个将单个输入转换为多个输入的方法:
public static Input1[] Transform(Input1 x)
{
if (x.Test == "a") return new[] {new Input1("a1"), new Input1("a2")};
if (x.Test == "b") return new[] {new Input1("b8"), new Input1("b9")};
return new[] {x};
}
(This is just from your toy example - I guess you actually need a transformation that is more meaningful.) (这只是来自您的玩具示例 - 我想您实际上需要一个更有意义的转换。)
Then you can just use SelectMany
to get your desired result in the correct order:然后您可以使用SelectMany
以正确的顺序获得所需的结果:
inputList
.SelectMany(Transform);
If you're using C# 8.0 or above, you may use switch expression as follows:如果您使用的是 C# 8.0 或更高版本,则可以使用如下switch 表达式:
var outputList =
inputList.SelectMany(x => x.Test switch
{
"a" => new[] { new Input1() { Test = "a1" }, new Input1() { Test = "a2" } },
"b" => new[] { new Input1() { Test = "b8" }, new Input1() { Test = "b9" } },
_ => new[] { x }
})
.ToList();
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