Question

I’m doing some calculations of comparing two strings. In case I know they are same length, is it more expensive to call isprefix or If (“string”==”string”) ?

Answer 1

Why not test? Easy enough to use the StopWatch class to compare, and include different length strings and different compare options.

I would expect no significant difference at the core, as IsPrefix is essentially:

public bool IsPrefix(string comp, string prefix) {
  return Compare(comp, 0, prefix.Length, prefix, 0, prefix.Length);
}

However there may be a difference between String’s operator == and CompareInfo class due to level of I18N applied.

In the end, you will need to measure, but I would expect that 99% of cases any difference is not significant to the overall application performance.