Question

Look at the following code:

StringBuilder row = TemplateManager.GetRow("xyz"); // no control over this method 
StringBuilder rows = new StringBuilder();

foreach(Record r in records)
{
    StringBuilder thisRow = new StringBuilder(row.ToString());
    thisRow.Replace("%firstName%", r.FirstName)
       .Replace("%lastName%", r.LastName)
          // all other replacement goes here
       .Replace("%LastModifiedDate%", r.LastModifiedDate);

    //finally append row to rows
    rows.Append(thisRow);
}

Currently 3 StringBuilders and row.ToString() is inside a loop. Is there any room for further optimization here?

Answer 1

I thought it might be quicker to replace thisRow with a string, but I did some tests and StringBuilder won.

String.Replace() creates a new string, which is expensive. StringBuilder.Replace() modifies the string in its buffer, which is less expensive. In my test I used a string of 500 chars and performed 6 Replace()‘s. StringBuilder was about 5% faster, including creating a new one each iteration.

However, one thing you should do is move the row.ToString() outside the loop. Calling it for each record is wasting cycles by creating a new string.

String row = TemplateManager.GetRow("xyz").ToString();
StringBuilder rows = new StringBuilder(); 

foreach(Record r in records) 
{ 
    StringBuilder thisRow = new StringBuilder(row);  
    thisRow.Replace("%firstName%", r.FirstName) 
                   .Replace("%lastName%", r.LastName) 
                   .Replace("%LastModifiedDate%", r.LastModifiedDate); 
    rows.Append(thisRow);
}