Variable Scope Reference

I am looking for a reference that explains how/why the scope of a variable affects performance. Here is an example of what I mean

Code:

---

    03/28/09  13:12:51.516    CPU - 1.794GHz.  Stopwatch(HR) Freq. is 3,579,545
    x86 Family 6 Model 13 Stepping 6    Address width - 32  Memory - 2.0GB
   
    One - Procedure
    Two - Module
    Outer Loops(OL) = 7    Inner Loops(IL) = 262,144
    Times given in ticks.  1 ms. = 10,000 ticks;  1,000 ms. = 1 second.
   
    Ticks / Loop    Fastest? One
    0.0194                1.2242                1.7381                -0.5139
    OL Base IL            One IL                Two IL                Difference (One - Two)
    1  5,055                320,265              454,974              -134,709
    2  5,086                320,411              454,639              -134,228
    3  5,058                320,113              455,677              -135,564
    4  5,093                320,022              455,077              -135,055
    5  5,057                324,892              459,133              -134,241
    6  5,247                319,998              455,082              -135,084
    7  5,057                320,722              454,889              -134,167
   
    Average
    5,093                320,917              455,638              -134,721    (-13.472 ms./IL)
   
    03/28/09  13:12:53.113  RunMode = CTRL-F5  End Dewayne Relative Speed Test
    Source Code Follows
        '
        Const itms As Integer = 100
        Dim TestData() As Integer
        Dim TestList As New List(Of Integer)
        Dim sum As Integer = 0
        '
        Private Function TestCase1() As Boolean 'One
            'Test One Code Follows
            Dim sum As Integer = 0
            For i As Integer = 0 To TestData.Length - 1
                sum += TestData(i)
            Next
            'End Test One Code
            Return True
        End Function
        '
        Private Function TestCase2() As Boolean 'Two
            'Test Two Code Follows
            sum = 0
            For i As Integer = 0 To TestData.Length - 1
                sum += TestData(i)
            Next
            'End Test Two Code
            Return True
        End Function
        '
        Private Sub _init()
            'Code needed to get the Test to run.  NOT part of the timing.
            'Only called once!!!
            TestList.Clear()
            For x As Integer = 1 To itms
                TestList.Add(Short.MaxValue)
            Next
            TestData = TestList.ToArray
        End Sub

---

What does the IL show you?

In one case you have a variable that is created on the stack and may well be retained in either the processor registers, or the cache, without having any real impact outside of the routine, while in the other case you have a variable created on the heap, which may have a read/write to system RAM for every iteration.

How do you look at the IL from VB Express(2008)? I have never done that.

Neither have I, since I don't use Express.

Might as well do a search to see if ILDASM is included on your computer. I would expect that it is there, but I never remember where it is located. I add it to the Tools menu with Tools|External Tools..., but I think that just lets you browse for tools, so you need to know where ILDASM is located, first.

Found it under 2003 SDK. I tried opening .exe's and it gave me an error "Failed to open meta data". Sounds like a title for a song 'I lost my meta data'