Question

I have a stringbuilder that I’m manipulating several times, and I need to replace strings within it with strings of varying lengths.

sb = new StringBuilder("This has {Count} Values.  Your search was '{SearchText}'.  Did you mean '{DidYouMean}'?")
//get the replacement areas, this would search for the field names within {}
MatchCollection matches = GetReplacementAreas(sb);

int indexOffset=0;
foreach(Match m in matches)
{
   //fields is a dictionary containing keys that match the fields
   sb.ReplaceAt(m.Index,m.Length,fields[m.Value]); 
}

Obviously ReplaceAt doesnt exist. I’m about to write it myself. Anybody else already done so?

Answer 1

public static class StringBuilderExtensions
{
#if EXTENSIONS_SUPPORTED
    public static StringBuilder ReplaceAt(this StringBuilder sb, string value, int index, int count)
    {
        return StringBuilderExtensions.ReplaceAt(sb, value, index, count);
    }
#endif

    public static StringBuilder ReplaceAt(StringBuilder sb, string value, int index, int count)
    {
        if (value == null)
        {
            sb.Remove(index, count);
        }
        else
        {
            int lengthOfValue = value.Length;

            if (lengthOfValue > count)
            {
                string valueToInsert = value.Substring(count);
                sb.Insert(index + count, valueToInsert);
            }
            if (lengthOfValue < count)
            {
                sb.Remove(index + count, lengthOfValue - count);
            }

            char[] valueChars = value.ToCharArray();
            for (int i = 0; i < lengthOfValue; i++)
            {
                sb[index + i] = valueChars[i];
            }
        }

        return sb;
    }
}