Search list elements with partial strings

Question

I have a List<string> who receives the phone number of all the contacts on the phone, until there is no problem, but I want to perform some operations with the elements of that list, but I am with some problems.

An example of possible result:

lst = {"*126", "[phone]", "12345678", "87654321", "3498761232"};

If you look, they’re all phone numbers, and I’ve stored them as a string to make it easier. Now I have to perform a search in this list, in all elements of the same (I do not know how many elements the list will have, because it depends on the user’s agenda).

Example: Typed user 123 in the textbox num and at the push of the button I search my list, the result should be:

[phone]
12345678
3498761232

For if we look, they are the only elements of the list that contains the typed string (123).

So briefly, how to search in a list of indeterminate size, a string that can be anywhere in the element (start, middle, end, etc), the search should return at most 3 values, that is, if we have another element as for example 51234251, despite containing 123 it would not be returned, because we already found 3 elements with 123 before him.

Sorry if you got confused, it was the most detailed way I could report, in short, is to search a partial string in a list and return the first three elements that contain that string. But I could not accomplish such a task, I hope someone can help me, because it has been a lot of work and time to figure out how to take the number of contacts and store in the list.

Answer 1

• Uses the extension Enumerable.Where to filter the list by a predicate.
• In this case, the predicate is: "the string must contain '123'". For this we can use String.Contains
• Usa Enumerable.Take to get the first n result elements and discard the remaining.

var input = "123";

var filtered = list.Where(s => s.Contains(input))
                   .Take(3)
                   .ToList();

https://dotnetfiddle.net/R0tiro