Don't worry. Not everyone knows it...

Importance of UI in performance Simple UI tricks, such as progress bars, redirecting user's attention using animation, or placing slower loading sections at the bottom of a page or off-screen, can often ‘fix’ a performance problem without the need to tune the underlying code. These UI tricks are an important tool to have in your performance tuning toolbox and can be much quicker and easier than addressing the underlying issue. They can act as a holdover until you have the time to devote to the core problem. So, one should never underestimate the UI while tackling performance issues. Isn't it interesting :)

Yes, if you are in a loop and adding to a string, then a StringBuilder *could* be most appropriate. However, the overhead of spinning up a StringBuilder instance makes the following pretty dumb:      var sb = new StringBuilder();  sb.Append("This is "); sb.Append("not more efficient"); sb.Append(" solution."); var str= sb.ToString();   Instead, use String.Join , which is typically more performant than spinning up a StringBuilder instance for a limited number of strings. It’s my go-to concat option:             string myString = String.Join(" ", new String[] { "This", "is", "a", "much", "better", solution, "."});   The first variable of " " can just be set to "" when you don’t want a delimiter. For loops that do a lot of looping, sure, use a StringBuilder. But just don’t assume it’s the de facto solution in all, or even the majority of cases. My rule of thumb ...