C# get also the key from parsing substring from string

November 17, 2022

I would like to refactor my method. I also need to get which value was first? So which anyOf? Is it possible to get it from here?

Example:

List<string> anyOf = new List<string>(){"at", "near", "by", "above"};
string source = "South Branch Raritan River near High Bridge at NJ"

public static int IndexOfAny(this string source, IEnumerable<string> anyOf, StringComparison stringComparisonType = StringComparison.CurrentCultureIgnoreCase)
{
    var founds = anyOf
        .Select(sub => source.IndexOf(sub, stringComparisonType))
        .Where(i => i >= 0);
    return founds.Any() ? founds.Min() : -1;
}

I would like to get back what is first in string. "near" or "at".

>Solution :

You could use:

public static (int index, string? firstMatch) IndexOfAny(this string source, IEnumerable<string> anyOf, StringComparison stringComparisonType = StringComparison.CurrentCultureIgnoreCase)
{
    return anyOf
        .Select(s => (Index: source.IndexOf(s, stringComparisonType), String: s))
        .Where(x => x.Index >= 0)
        .DefaultIfEmpty((-1, null))
        .First();
}