What is the most elegant way to implement GetTextAfterMarker()

Question

Here is another old function I have from my C# 1 days, what would be a more elegant way to write it:

//method: gets the text in a string in front of a marker, if marker is not there, then return empty string
//example: GetTextAfterMarker("documents/jan/letter043.doc","/") returns "documents"
//example: GetTextAfterMarker("letter043.doc","/") returns ""
//rank:8
public static string GetTextAfterMarker(string line, string marker)  {
    string r = "";

    int pos = line.IndexOf(marker);
    if(pos != -1) {
        r = line.Substring(pos+(marker.Length),line.Length-pos-(marker.Length));
    } else {
        r = "";
    }

    return r;
}

Answer 1

You could use regular expressions:

    public static string GetTextBeforeMarker(string line, string marker)
    {
        if (String.IsNullOrEmpty(line))
            throw new ArgumentException("line is null or empty.", "line");
        if (String.IsNullOrEmpty(marker))
            throw new ArgumentException("marker is null or empty.", "marker");
        string EscapedMarker = Regex.Escape(marker);
        return Regex.Match(line, "([^" + EscapedMarker + "]+)" + EscapedMarker).Groups[1].Value;
    }

Answer 2

I find the name somewhat strange, given that it should return the text appearing before the first marker. But this one does the same job, I think (I took the liberty to change the name):

public static string GetTextBeforeMarker(string line, string marker)
{
    if (line == null)
    {
        throw new ArgumentNullException("line");
    }

    if (marker == null)
    {
        throw new ArgumentNullException("marker");
    }

    string result = line.Split(new string[] { marker }, StringSplitOptions.None)[0];
    return line.Equals(result) ? string.Empty : result;
}

Explanation: split the string into an array using the marker as split argument. If the first element of the result is the same as the input, the marker was not in the string, so we return an empty string, otherwise we return the first element (which is the text up to the first occurrence of the marker).

Answer 3

Am I missing something? Wouldn't this be more simple? Also I prefer Substring to Split.

public static string GetTextAfterMarker(string line, string marker)  {
    int pos = line.IndexOf(marker);
    if (pos == -1)
       return string.Empty;
    return line.Substring(0,pos);
}

Answer 4

public static string GetTextBeforeMarker(string line, string marker)  {
    return GetTextAfterMarker(string line, string marker);
}