Comments by halex2005 (Top 4 by date)

Reason for my vote of 3
Reading "effective c " book solve this unprofessional thinking.

Reason for my vote of 3
Check my comment with three corrections. Your exapmle runs very fast and error of elapsed time calculation occurs. I don't belive in your current result.

I think that time results have an errors of calculation.

1) Try to use more precise System.Diagnostics.Stopwatch class for elapsed time calculations.

2) Make time calculation for loop:
{
get time
loop (counter in range(0,n))
{
your string concat/format test
}
get time, calculate elapsed time
}
I recommend you select variable n to value that corresponds elapsed time about one second for one of resuls.

3) insert space in format string between parameters {0} and {1} for correct result of concatenation.