>Yes, I remember looking at that some time ago and I posted the results here
>Up the 4 args and you get a call tho String.Concat( 2 to 4 args overload)
>More than 4 - an array of string[] is created putting each arg into the array
>Then String.Concat( string[] ) gets called
>http://msdn.microsoft.com/en-us/library/System.String.Concat.aspx
>
>>I'd expect

var stringres;
>>stringres = "";
>>stringres = stringres + str1;
>>stringres = stringres + str2;
>>stringres = stringres + str3;

>>to be rewritten to form 1 by an optimizing compiler as such code can be found - if they can inline whole functions, inlining concats should be easy
>
>No, I had checked before replying
>
>Ildasm shows three calls to String.Concat(string, string)

Wow - not much optimization in that stage. And if they made the effort for 4 args in ILDASM, that hints at no such optimization when compiling to machine code. The Java Hotspot JVM optimizes some such string operations, even recursive, if given those parameters...