如何获得比数组字符串少的值

Question

string[] str = new string[] {"sun", "mon", "tue", "wed", "thu", "fri","sat"};

是否可以使用LINQ在输入字符串之前获取索引列表：即，如果输入字符串是thu ，我的结果应该是： sun,mon,tue,wed,thu 。

Answer 1

You can use the Take() extension method:

str.Take(Array.IndexOf(str, "thu") + 1).ToArray();
// --> returns `["sun", "mon", "tue", "wed", "thu"]`

Answer 2

If you want the items before the input string you can write:

res = str.TakeWhile (s => s != "thu");

This will however not include thu itself.

But can by fixed by writing:

res = str.TakeWhile (s => s != "thu").Concat(new[]{"thu"});

But the fastest way of doing it would probably be:

var i = Array.IndexOf(str, "thu");
if(i != -1)
{
    var target = new string[i + 1];
    Array.Copy(str, target, i + 1);
}

Answer 3

You can try the IndexOf with Where method on a list instead of an array. Here is the code:

string[] str = new string[] { "sun", "mon", "tue", "wed", "thu", "fri", "sat" };

var strList = str.ToList();

var targetIndex = strList.IndexOf("thu");

var result = strList.Where((s, index) => index <= targetIndex).ToList();
//result = sun, mon, tue, wed, thu

Answer 4

var query = str.TakeWhile(s => s != "thu").Concat(new string[] { "thu" }).ToArray();