Finding multiple indexes from source string

Question

Hello,

Basically I need to do String.IndexOf() and I need to get array of indexes from the source string.

Is there easy way to get array of indexes?

Before asking this question I have Googled a lot, but have not found easy solution to solve this simple problem.

Answer 1

How about this extension method:

public static IEnumerable<int> IndexesOf(this string haystack, string needle)
{
    int lastIndex = 0;
    while (true)
    {
        int index = haystack.IndexOf(needle, lastIndex);
        if (index == -1)
        {
            yield break;
        }
        yield return index;
        lastIndex = index + needle.Length;
    }
}

Note that when looking for "AA" in "XAAAY" this code will now only yield 1.

If you really need an array, call ToArray() on the result. (This is assuming .NET 3.5 and hence LINQ support.)

Answer 2

You would have to loop, I suspect:

        int start = 0;
        string s = "abcdeafghaji";
        int index;
        while ((index = s.IndexOf('a', start)) >= 0)
        {
            Console.WriteLine(index);
            start = index + 1;
        }

Answer 3

    var indexs = "Prashant".MultipleIndex('a');

//Extension Method's Class
    public static class Extensions
    {
         static int i = 0;

         public static int[] MultipleIndex(this string StringValue, char chChar)
         {

           var indexs = from rgChar in StringValue
                        where rgChar == chChar && i != StringValue.IndexOf(rgChar, i + 1)
                        select new { Index = StringValue.IndexOf(rgChar, i + 1), Increament = (i = i + StringValue.IndexOf(rgChar)) };
            i = 0;
            return indexs.Select(p => p.Index).ToArray<int>();
          }
    }