Why doesn't StringBuilder have IndexOf method?

Question

I understand that I can call ToString().IndexOf(...), but I don't want to create an extra string. I understand that I can write a search routine manually. I just wonder why such a routine doesn't already exist in the framework.

Answer 1

I know this is an old question, however I have written a extension method that performs an IndexOf on a StringBuilder. It is below. I hope it helps anyone that finds this question, either from a Google search or searching StackOverflow.

/// <summary> /// Returns the index of the start of the contents in a StringBuilder /// </summary>         /// <param name="value">The string to find</param> /// <param name="startIndex">The starting index.</param> /// <param name="ignoreCase">if set to <c>true</c> it will ignore case</param> /// <returns></returns> public static int IndexOf(this StringBuilder sb, string value, int startIndex, bool ignoreCase) {                 int index;     int length = value.Length;     int maxSearchLength = (sb.Length - length) + 1;      if (ignoreCase)     {         for (int i = startIndex; i < maxSearchLength; ++i)         {             if (Char.ToLower(sb[i]) == Char.ToLower(value[0]))             {                 index = 1;                 while ((index < length) && (Char.ToLower(sb[i + index]) == Char.ToLower(value[index])))                     ++index;                  if (index == length)                     return i;             }         }          return -1;     }      for (int i = startIndex; i < maxSearchLength; ++i)     {         if (sb[i] == value[0])         {             index = 1;             while ((index < length) && (sb[i + index] == value[index]))                 ++index;              if (index == length)                 return i;         }     }      return -1; }