First index before a position

Question

I have a string and index in that string, and want to get the first position of a substring before that index.

e.g., in string:

\"this is a test string tha

Answer 1

So you want the last index before a given index...

var myString = "this is a test string that contains other string for testing";
myString = String.SubString(0, 53);
var lastIndexOf = myString.LastIndexOf("string");

Answer 2

You can simply take the substring from 0 to index and on this substring ask for the last index of it

YourString.substring(0,index).LastIndexOf("string");

Answer 3

Like IndexOf() where you can start, lastIndexOf also gives you a place to start from going backwards

var myString = "this is a test string that contains other string for testing";
var lastIndexOf = myString.LastIndexOf("string", 30);

Reports the zero-based index position of the last occurrence of a specified string within this instance. The search starts at a specified character position and proceeds backward toward the beginning of the string.

Answer 4

Try something like:

var res = yourString.Substring(0, index).LastIndexOf(stringToMatch);

Answer 5

I know I am late to the party but this is the solution that I am using:

    public static int FindIndexBefore(this string text, int startIndex, string searchString)
    {
        for (int index = startIndex; index >= 0; index--)
        {
            if (text.Substring(index, searchString.Length) == searchString)
            {
                return index;
            }
        }

        return -1;
    }

I tested it on your example and it gave the expected results.