Capturing strings between stopwords

private string StringBetween(string beginTag, string endTag, string texteToParse)
{
    System.Collections.Specialized.StringCollection coll = StringsBetween(beginTag, endTag, texteToParse);
    if (coll.Count == 0) return "";
    else return coll[0];
}
private System.Collections.Specialized.StringCollection StringsBetween(string beginTag, string endTag, string texteToParse)
{
    System.Collections.Specialized.StringCollection result = new System.Collections.Specialized.StringCollection();
    int pos1, pos2;
    pos1 = 0;
    pos2 = -1;
    pos1 = texteToParse.IndexOf(beginTag);
    while (pos1 > -1)
    {
        pos2 = texteToParse.IndexOf(endTag, pos1 + beginTag.Length);
        if (pos2 > -1)
        {
            result.Add(texteToParse.Substring(pos1 + beginTag.Length, pos2 - (pos1 + beginTag.Length)));
            pos1 = texteToParse.IndexOf(beginTag, pos2 + endTag.Length);

        }
        else
            pos1 = -1;

    }
    return result;
}