使用双精度列表中的 foreach 循环创建字符串列表。 每两个值必须压缩成一个字符串，然后添加到列表中

Question

I hope someone has a good was of solving this problem.

So I have a list of doubles these being coordinates, example -123123, 12313. shown in image below.

List of doubles

these are being used in this foreach loop:

foreach (var coord in element.geometry.coordinates)
{


}

I'm trying to make a list of said coordinates - but instead of them being a list of single coordinates I need them to be compressed into two.

So rather than a list of

• -1213123
• 1345
• -345
• 1234535

I need a list of strings like so.

• -1213123, 1345
• -345, 1234535

using var 'coord' this being a single coordinate when coming out of the foreach loop. how can I create a list pairing every two values that come out of the loop.

Thanks for any help given :)

Answer 1

if the foreach loop is compulsory, then

string[] lst = new string[element.geometry.coordinates.Count() / 2];

int i=0;
foreach (var coord in element.geometry.coordinates)
{
    if (i % 2 == 1) 
        lst[i-1] = $"{lst[i-1]}, coord";
    else
        lst[i] = coord

    ++i;

}

Answer 2

I know it looks a little bit weird, but you can you Linq.Zip method.

        var coordinates = element.geometry.coordinates;
        var result = coordinates
            .Where((_, index) => index % 2 == 0) // Get even numbers
            .Zip(
                coordinates.Where((_, index) => index % 2 == 1), // Get odd numbers
                (first, second) => $"{first}, {second}") // Zip them together
            .ToList(); // If you need the result as List<string>

Answer 3

You cannot take a step other than 1 in a foreach loop. Therefore I propose to use a for loop instead. It can be set to step 2.

var doubles = new List<double> { -1213123, 1345, -345, 1234535 };
var strings = new List<string>();

for (int i = 0; i < doubles.Count; i += 2)
{
    strings.Add(doubles[i] + ", " + doubles[i + 1]);
}

Do not need extra conditional if statements. This solution turns out to be as simple and effective as possible.