Thanks Jon for the detailed explanation. Much appreciated.
On Thu, Jun 28, 2012 at 7:37 PM, Jonathan Pryor <j...@xamarin.com> wrote:
> On Jun 28, 2012, at 4:10 AM, Matthew Leibowitz wrote:
> > Although this won't solve your problem, string + string is a bad
> practice. It is better to use a StringBuilder:
>
> string.operator+() _may_ be a bad practice. In this case, it is NOT a bad
> practice; it is fine.
>
> Specifically, StringBuilder is amortized O(n), so it may need to resize
> the internal buffer, allocating more memory.
>
> string.operator+, on the other hand, has two compiler features:
>
> 1. String constants are concatenated at compile-time. This expression:
>
> "a" + "b" + "c"
>
> is translated by the compiler into:
>
> "abc"
>
> 2. When concatenating non-constant strings, all of them are passed to
> string.Concat() at once, and string.Concat() is able to allocate a buffer
> large enough to store _all_ the strings at once, no resize needed. This
> expression:
>
> Name + "\n" + Unit + "\n" + AddressLine1
>
> is generated as:
>
> string.Concat (Name, "\n", Unit, "\n", AddressLine1)
>
> StringBuilder will ~always have "slack"/extra memory involved.
> String.Concat() never will...for the expression it's involved with.
>
> Thus the real question when comparing string.operator+ to StringBuilder is
> whether you have "intermediate named temporaries," for example with loops.
> If you're using a (non-compiler-generatd) "temporary" variable, you should
> normally prefer StringBuilder;
>
> // BAD
> string val = "";
> for (int i = 0; i < 1000; ++i)
> val += i + " ";
> return val;
>
> // GOOD
> var sb = new StringBuilder();
> for (int i = 0; i < 1000; ++i)
> sb.Append (i).Append (" ");
> return sb.ToString ();
>
> - Jon
>
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