Convert List to List> using Linq [duplicate]

Answer 1

var output = Enumerable.Range(0, input.Count / 2)
                       .Select(i => Tuple.Create(input[i * 2], input[i * 2 + 1]))
                       .ToList();

Answer 2

You could use this:

IEnumerable<KeyValuePair<string, string>> list = 
        input.Where((s, i) => i % 2 == 0)
             .Select((s, i) => new KeyValuePair<string, string>(s, input.ElementAt(i * 2 + 1)));

Answer 3

You can use LINQ Aggregate() function (the code is longer than a simple loop):

var result = 
input.Aggregate(new List<List<string>>(),
                (acc, s) =>
                {
                    if (acc.Count == 0 || acc[acc.Count - 1].Count == 2)
                        acc.Add(new List<string>(2) { s });
                    else
                        acc[acc.Count - 1].Add(s);
                    return acc;
                })
                .Select(x => new KeyValuePair<string, string>(x[0], x[1]))
                .ToList();

N.B.
this works even if your initial input becomes a generic IEnumerable<string> and not specifically a List<string>

Answer 4

I wouldn't suggest using LINQ here as there is really no reason to and you don't gain anything by using LINQ, but simply using a normal for loop and increasing your counting variable by two in each iteration:

var result = new List<KeyValuePair<string, string>>();

for (int index = 1; index < input.Count; index += 2)
{
    result.Add(new KeyValuePair<string, string>(input[index - 1], input[index]));
}

Note that I'm starting my index with 1 so I don't run into an exception for accessing an invalid index in case the number of items in input is odd, i.e. if input ends with a "half pair" of values.