Read legacy vb5 files with variant declare in vb.net

[Guest]

I have old legacy code from vb5 where data was written to a file with a
variant declaration (this was actually a coding error?)...

in vb5 the code was:

Dim thisdata as integer
Dim thatdata
Dim someother as integer

thatdata = ubound( Array1 )

Put 1, , thisdata
Put 1, , thatdata
Put 1, , someother

So "thatdata" was variant by default, then given an integer by ubound?

Now I need to read the old files created from this code using vb.net. I cant
figure out how to declare the variables.

I have tried declaring all the types I know of ie short, integer, single,
tried strings etc.

In vb.net I use:

Dim thisdata as short
Dim thatdata as ?????
Dim someother as integer

FileOpen(1, FileName$, OpenMode.Binary, OpenAccess.Read)

FileGet(1, thisdata )
FileGet(1, thatdata )
FileGet(1, someother )

The data is good until thatdata, then everything is junk.

What would the old vb5 code have written in this case? Must have choosen
some format? How can I read it now in vb.net? I realize the variant was
dropped/changed in .net? But I still need to read the old files.

BTW, this is a simplified version of the actual code/file structure where I
have the problem. I have not tried the above code and not sure it will
duplicate the problem exactly.

It is very important to be able to read these old data files.

Thanks in advance,

Tom

 

[rowe_newsgroups]

Dim thatdata as ?????

Dim thatdata as Object

In .NET everything is an object, so you could say that "Object" is now
the hold-all type. And if you were wondering, you no longer need to use
the Set keyword when working with objects. You should then be able to
use DirectCast() to attempt to convert "thatdata" to whatever type you
need.

Thanks,

Seth Rowe

 

[Guest]

Thanks, I see. But, I tried it previously declaring as object as you suggest,
and I still dont read the value correctly in .net. I know the real thatdata
value is 12. But I read 3. etc. And all values following are a jumble.

I or it dont seem to know what length variable to read, or what kind of
object to be. I need to know what vb5 would have written, what kind of object
was the variant in vb5?? then I can tell .net what to read?

 

[rowe_newsgroups]

So how is this file formatted? Or could you even post a little of the
file so I could see what is going on? Also what code are you using to
parse the file? Maybe you're casting the object improperly.

Thanks,

Seth Rowe

 

[Michael D. Ober]

You don't by any chance have 1 and 2 as consecutive characters in your
source data file. If so, the operation 1 + 2 is ambiguous since the
characters are read from the file as strings and adding two strings can be
done via string concatination. In VB 6 and earlier, 1 + 2 would normally
return 3, but it could, on occassion, return 12. In VB 2005, the reverse is
true.

Mike Ober.

 

[Guest]

Thanks for looking. Ok, I made an example. I am using VB6 as I dont have VB5
installed but I am duplicating the problem with this simple code:

***********
The VB6 code (make a form with two buttons and you can read and write the
file):


Dim variable1 As Integer
Dim variable2 As Integer
Dim variable3
Dim variable4 As Integer

Private Sub Form_Load()

Dim anarray(9) As String

variable1 = 1
variable2 = 2
variable3 = UBound(anarray)
variable4 = 4


End Sub

Private Sub WriteCommand1_Click()

Open "c:\tomtemp\test1.dat" For Binary Lock Read Write As 1

Put 1, , variable1
Put 1, , variable2
Put 1, , variable3
Put 1, , variable4

Close

End Sub

Private Sub ReadCommand2_Click()

Open "c:\tomtemp\test1.dat" For Binary Lock Read Write As 1

Get 1, , variable1
Get 1, , variable2
Get 1, , variable3
Get 1, , variable4

Close

End Sub




********************
the vb.net code:


Dim variable1 As Short
Dim variable2 As Short
Dim variable3
Dim variable4 As Short

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load


FileOpen(1, "c:\tomtemp\test1.dat", OpenMode.Binary, OpenAccess.Read)

FileGet(1, variable1)
FileGet(1, variable2)
FileGet(1, variable3)
FileGet(1, variable4)



FileClose(1)


End Sub


***************************


Put whatever after the variable3 delare and watch the value of variable 3
(or error), which should be "9". I give the variable3 a value using ubound
since that is what happens in the original, not sure if it matters. It should
make variable3 an integer? But .....as you can see... waaaa?

Thanks again,

Tom

 

[Guest]

Michael,

I dont think so. But there are many data files to read that could have
anything in them.

See my other earlier post from today for an example you can duplicate.

 

[Michael D. Ober]

Tracks,

Something that might help is to put the following statements at the top of
the code file:

Option Explicit On ' Require variable declaration
Option Strict On ' Enforce Type Safety

With these two statements, the VB 2005 compiler will refuse to compile
ambiguous code such as

dim a
dim b
dim c

c = a + b

You'll get an error on the addition that you will need to resolve before you
can compile.

Mike.