score:9

Accepted answer

I would try the following:

count = mylist.Count(s => myString.Contains(s));

score:0

This is one approach, but it's limited to 1 character matches. For your described scenario of numbers from 1-9 this works fine. Notice the s[0] usage which refers to the list items as a character. For example, if you had "12" in your list, it wouldn't work correctly.

string input = "123456123";
var list = new List<string> { "1", "4" };
var query = list.Select(s => new
                {
                    Value = s,
                    Count = input.Count(c => c == s[0])
                });

foreach (var item in query)
{
    Console.WriteLine("{0} occurred {1} time(s)", item.Value, item.Count);
}

For multiple character matches, which would correctly count the occurrences of "12", the Regex class comes in handy:

var query = list.Select(s => new
                {
                    Value = s,
                    Count = Regex.Matches(input, s).Count
                });

score:0

Try

count = myList.Count(s => s==myString);

score:6

It is not perfectly clear what you need, but these are some options that could help:

myList.Where(s => s == myString).Count()

or

myList.Where(s => s.Contains(myString)).Count()

the first would return the number of strings in the list that are the same as yours, the second would return the number of strings that contain yours. If neither works, please make your question more clear.

score:1

If myList is just List<string>, then this should work:

int count = myList.Count(x => myString.Contains(x));

If myList is List<List<string>>:

int count = myList.SelectMany(x => x).Count(s => myString.Contains(s));

score:0

try

var count = myList.Count(x => myString.ToCharArray().Contains(x[0]));

this will only work if the item in myList is a single digit

Edit: as you probably noticed this will convert myString to a char array multiple times so it would be better to have

var myStringArray = myString.ToCharArray();
var count = myList.Count(x => myStringArray.Contains(x[0]));

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