What's the performance consequence using the 'With' keyword in vb.net instead of using reusing the instance name over and over?
asked Jan 13, 2010 at 0:49
Shimmy Weitzhandler
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3 Answers
Assuming that you're comparing it to a local variable reference, there is no difference whatsoever; both will emit the exact same IL. (At least in Release mode)
However, if you're comparing it to repeated invocations of a property or indexer, With will be a little bit faster, and if you're comparing it to repeated invocations of a method, it might be much faster. (The With keyword will create a local variable and assign it to the object that you With'd, so the method will only be called once instead of on every line)
3 Comments
MarkJ
+1. Although I'd say you should only worry about these performance differences if you've measured and found a serious performance bottleneck in a specific block of code that uses With. "Premature micro-optimization is the root of all evil"
Shimmy Weitzhandler
@MarkJ I'm talking about a huge batch operation (1000000+) entries
toddmo
I didn't know you could use
With with a method. Cool!There is no runtime performance cost. It is just "syntactic sugar" to make your code look prettier.
1 Comment
SuperDre
It's not just "syntactic sugar", but it depends on what you're using at the time, see the answer by @Slaks.
sub xyz (ByRef param as MyObj)
'Local ref, same as with
dim o2 as YourObject = param.YourObject
o2.callSomething()
'Bad performance
param.YourObject.callSomething()
end sub
2 Comments
brimborium
Please also provide some explanation to your answer as to how it answers the question.
SuperDre
Actuall your example is wrong, in your example the param.YourObject.callSomething() is faster as there is no subsequent call to YourObject and therefore the setup of the variable o2 is only extra overhead (unless ofcourse the compiler optimizes it to the same as param.YourObject.callSomething(). But if you call another function on YourObject after using .callSomething(), then using the o2 local ref would be faster.