C# third index of a character in a string

Question

is there a command that can get the third index of a character in a string? For example:

error: file.ext: line 10: invalid command [test:)]

Answer 1

int pos = -1;
for ( int k = 0; k < 3; ++k )
{
  pos = s.indexOf( ':', pos+1 );
  // Check if pos < 0...
}

Answer 2

String.IndexOf will get you the index of the first, but has overloads giving a starting point. So you can use a the result of the first IndexOf plus one as the starting point for the next. And then just accumulate indexes a sufficient number of times:

var offset = myString.IndexOf(':');
offset = myString.IndexOf(':', offset+1);
var result = myString.IndexOf(':', offset+1);

Add error handling unless you know that myString contains at least three colons.

Answer 3

Please see this answer on a similar question: https://stackoverflow.com/a/46460083/7673306
It provides a method for you to find the index of nth occurrence of a specific character within a designated string.

In your specific case it would be implemented like so:

int index = IndexOfNthCharacter("error: file.ext: line 10: invalid command [test:)]", 3, ':');

Answer 4

Simply split the string by the char. This gives you an array that you can then use to target what you want.

var stringToSplit = "one_two_three_four";
var splitString = stringToSplit.Split("_");          
if (splitString.length > 3){
    var newString = $"{splitResult[0]}_{splitResult[1]}_{splitResult[2]}";
}

Answer 5

You could write something like:

    public static int CustomIndexOf(this string source, char toFind, int position)
    {
        int index = -1;
        for (int i = 0; i < position; i++)
        {
            index = source.IndexOf(toFind, index + 1);

            if (index == -1)
                break;
        }

        return index;
    }

EDIT: Obviously you have to use it as follows:

int colonPosition = myString.CustomIndexOf(',', 3);

Answer 6

I am guessing you want to parse that string into different parts.

public static void Main() {
    var input = @"error: file.ext: line 10: invalid command [test (: ]";
    var splitted = input .Split(separator: new[] {": "}, count: 4, options: StringSplitOptions.None);

    var severity = splitted[0]; // "error"
    var filename = splitted[1]; // "file.ext"
    var line = splitted[2];     // "line 10"
    var message = splitted[3];  // "invalid command [test (: ]"
}