[RESOLVED] [2005] For...Next vs. Do...While

[Troy Lundin]

When I open my assemblies in Reflector, my for...next loops are rewritten like so:

Original Loop:

For i As Int32 = 0 To 30 Step 1
' Do something
Next i

Rewritten Loop:

Dim i As Integer
Do While (i <= 30)
' Do something
i += 1
Loop

I have also seen (and used):

Dim i As Integer
Do
' Do something
i += 1
Loop While (i <= 30)

Is there any performance difference between those? Or any difference other than the obvious aesthetic one?

[VBDT]

I don't think there should be any significant difference. Although I would recommend using Integer instead of Int32. Because for two reasons:
1. Integer is faster then Int32
2. Integer will work in 64bit system but Int32 will throw an exeption.

[penagate]

Is there any performance difference between those? Or any difference other than the obvious aesthetic one?

No, that's just how For loops get compiled to bytecode.

1. Integer is faster then Int32

As far as I know, Integer is mapped to either Int32 or Int64 depending on the platform, so I can't see how this could be true.

[VBDT]

No, that's just how For loops get compiled to bytecode.



As far as I know, Integer is mapped to either Int32 or Int64 depending on the platform, so I can't see how this could be true.

Hi penagate, This is from MSDN:

"The Integer data type provides optimal performance on a 32-bit processor. The other integral types are slower to load and store from and to memory."

[Troy Lundin]

Are you positive that the "other integral types" it mentions are not Byte, Short and Long?