Vb: how to declare about 1000 stringbuilders by code

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This is my code that does not work, but it demonstrates what I need to do:
create about 1000 stringbuilders who's name is defined by a string of two characters (names defined by the records in file "C:\Temp\NGDDIVlist.txt").

Record = Split(File.ReadAllText("C:\Temp\NGDDIVlist.txt"), vbCrLf)
'Record holds the names for the stringbuilders
        For i = 0 To Record.length-1
            Dim Record(i) As StringBuilder
        Next

It is not possible to declare a variable where the name of this variable is a "string"... How can I overcome this issue?

More explanation:
Well, the question really is:
On a daily basis a textfile is generated with about a million strings (C:\Temp\NGDDIVlist.txt). Each string is in fact a record with two fields. The project needs to search this textfile for matches on field 0 of each record and has to do that for more or less 400.000 times. For the time being this is done using Instr, but I am looking for faster ways to do this. If I can split up the initial textfile in less longer subfiles, the Instr will take less time. Therefore these subfiles need to be named with the 'key' used for splitting. For this key I want to use the last two characters of field 0 of each record in the initial textfile. To build those subfiles fast, I want to use stringbuilders and since the 'key' = 2 characters, there are 36 x 36 = cases...

What I have tried:

see the code
searched the internet for solutions but didn't find any

Posted 8-Jul-19 8:07am

CDRxxx

Updated 9-Jul-19 9:12am

v2

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Comments

Maciej Los 8-Jul-19 14:10pm

Why do you need to create over 1000 stringbuilders? This sounds very strange...

MadMyche 8-Jul-19 15:02pm

Is this just VB (as in VB6) or is this VB.Net?

3 solutions

Solution 3

Thanks to "OriginalGriff" & "Patrice T".
Both responses are helpfull!

I did, for the time beeing, adapt the procedure by splitting up the file 'to check' in 1296 (36x36) subfiles. The splitting up takes 10 Sec, but the searches later on directly in the right subfile speeds up the overall proces significantly!

On the other hand, I need to study the ways I can handle in VB textfiles as indexed dB files... I'm looking now into dictionary ...

Posted 9-Jul-19 9:12am

CDRxxx

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Maciej Los 9-Jul-19 15:31pm

This is not answer. PLease, delete it to avoid down-voting. Such of content should be posted as a comment to the solution.

Patrice T 9-Jul-19 15:42pm

Hi,
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OriginalGriff · Accepted Answer · 2019-07-08T08:33:00

Record is already defined: it's an array of strings, because that is what Split returns.
You could create an array of StringBuilder under a different name:

VB

Dim builders As StringBuilder() = New StringBuilder(Record.Length - 1) {}

For i As Integer = 0 To Records.Length - 1
    builders(i) = New StringBuilder(Records(i))
Next

But ... unless you propose to alter them, it's a pointless and memory consuming thing to do!

You can't define variables at runtime using a string as the name: you could use a Dictionary to do something similar:

VB

    Dim builders As Dictionary(Of String, StringBuilder) = New Dictionary(Of String, StringBuilder)()

    For i As Integer = 0 To Records.Length - 1
        builders(Record(i)) = New StringBuilder()
    Next
End Sub

And access each StringBuilder separately via builders

VB

builders("AB").Append("Some text")
Console.WriteLine(builders("XY").ToString())

But to be honest, I think you are overthinking this and would be better off taking a step back and asking yourself what you are doing that you think this is a good idea. This doesn't seem like a good solution to any real world problem to me, and then normally means there have been some fundamental poor decisions made earlier on in the project design.

Patrice T · Accepted Answer · 2019-07-08T13:12:00

Quote:
Vb: how to declare about 1000 stringbuilders by code

You try things to get a working solution, this is a good state of mind, but in your case, your 'Solution' smells like a wrong approach to your problem.

From the information you gave, I would look at dictionary and databases.

Using Instr is very simple minded, but is not efficient on long strings, breaking the file in 1200 part will improve the runtime, but each part is still about 1000 records and Instr can match in second field, which you have to handle.
With dictionary or database (with index) a search on full file is done in about scanning 20 records and only on first field.
The 20 comes from the fact that both dictionary and database are using an ordered list of records and a search is done by dichotomy, 1000000 records is about 2^20, so 20 keys to check for a search.

VBA Dictionary - Using the VBA Dictionary. Key Value pairs[^]

Advice: learn about structures and objects available, it can only help you to choose wise.

Vb: how to declare about 1000 stringbuilders by code

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