如何在LINQ中获得数组索引 [英] How to get an array index in LINQ

问题描述

我从两个单独的来源(我无法控制)获得两个字符串作为输入.第一个字符串strInput将包含一个"X"，其位置应等于pattern字符串中元素的值.我需要pattern中元素的索引.

我已经使用``for''循环在常规代码中工作了，但是想使用LINQ和/或lambda使其更加简洁.以下返回值4，但我需要的是索引，在这种情况下为"1".

I get two strings as input from two separate sources (over which I have no control). The first string strInput will contain one ''X'', the position of which should be equal to the value of an element in the pattern string. I need the index of the element in pattern.

I''ve got it working in regular code using ''for'' loops but would like to use LINQ and/or lambdas to make it more succinct. The following returns the value 4, but what I need is the index, which in this case is ''1''.

string strInput = "    X       ";           // String from form (this is 4 spaces followed by X followed by n spaces
string pattern = "0,4,6,8,11";              // String containing matching positions of X in string

string place = strInput.IndexOf("X").ToString();        // Get position of X
string[] positions = pattern.Split(',');

var thisIndex = from pos in positions
                where (pos == place)
                select pos.First();

foreach (var x in thisIndex)
{
    Console.WriteLine("This is the index of X: {0}", x);
    Console.ReadLine();
}

任何帮助将不胜感激.

Any help would be appreciated.

推荐答案

安妮，你好！

试试这个.

Hi Annie!

Try this.

string strInput = "    X       "; // String from form (this is 4 spaces followed by X followed by n spaces
string pattern = "0,4,6,8,11"; // String containing matching positions of X in string

string place = strInput.IndexOf("X").ToString();        // Get position of X (4)
string[] positions = pattern.Split(",");

//Create a temporary structure saving the positions along with their positions.
var result = positions.Select((s, i) => new { Pos = i, Str = s }) 
            .Where(o => o.Str == place) //Pick the item with a position matching the input
            .FirstOrDefault();

if (result != null)
{
    var output = result.Pos;
}

此解决方案更为简洁，但请注意，它要求输入始终有效，因此您可能需要进行一些初始检查.

This solution is much more succinct, but note that it requires the input to always be valid, so you might want to do some initial checking.

string strInput = "    X       ";           // String from form (this is 4 spaces followed by X followed by n spaces
string pattern = "0,4,6,8,11";              // String containing matching positions of X in string

int place = strInput.IndexOf("X");        // Get position of X (4)
var positions = pattern.Split(",").Select(s => int.Parse(s));

int result = positions.TakeWhile((p, i) => p != place)
                      .Count();

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