Lookup / search value from a file

[dotdotdot]

Dear all,

I’m very new to VB and without much experience in programming. Any advice or direction would be helpful to me.

I’m writing a programme that, when I get a certain integer value from a message, I have to return a string of characters. Sounds simple if there is only a handful of integers, I could get away with few IF statements. BUT, such is life, there is a very large number of possible values.

My guess is that, if I have a separate file to store the corresponding characters, I could change the characters easily, and the programme itself could be smaller.

My questions are:
*What would be the best type of file to store the ‘lookup table’?
*How could I access the file quickly and search for corresponding characters?
*How do I read just one line of the file and not more?

I would greatly appreciate if anyone could give me any advice or example links.

Thanks in advance
Thomson

 

[MattP]

I suggest looking at the database section of the forums on how to use parameterized queries. This way you can keep 1 centralized lookup table for multiple clients.

-----

Another option would be to use an XML file. Here's a sample layout and function to pull the string value using an XPath expression.

<?xml version="1.0" encoding="utf-8" ?>
<TopLevel>
  <Conversion>
    <IntegerCode>1</IntegerCode>
    <ActualString>1st value</ActualString>
  </Conversion>
  <Conversion>
    <IntegerCode>2</IntegerCode>
    <ActualString>2nd value</ActualString>
  </Conversion>
</TopLevel>

Private Function StringLookup(ByVal MyInteger As Integer) As String

    Dim xdoc As New XPathDocument("Components\IntLookup.xml")
    Dim nav As XPathNavigator = xdoc.CreateNavigator()
    Dim iterator As XPathNodeIterator = _
        nav.Select(String.Format("//IntegerCode[.'{0}']/parent::node()/ActualString", MyInteger))
    iterator.MoveNext()

    Return iterator.Current.Value
End Function

 

[dotdotdot]

MattP,

Thanks for the suggestion, I'll ask gurus in the database forum.

Thanks

 

[dotdotdot]

Matt,

Thanks for the code, but one more followup question. How could I have multiple sections on the xml?

Because the messages I receive comes in few types, they may contain the same integer, but would raise a different response message. If I want to keep all the response messages in one XML file, how could I alter the code to do so?

Cheers,
T

 

[MattP]

Matt,

Thanks for the code, but one more followup question. How could I have multiple sections on the xml?

Because the messages I receive comes in few types, they may contain the same integer, but would raise a different response message. If I want to keep all the response messages in one XML file, how could I alter the code to do so?

Cheers,
T

So your're going to receive 1 and could have multiple responses you could give back? I would seriously consider revising your program while it's still in the planning phase. If it's out of your hands I'd just add another element to your conversion XML.

  ....
  <Conversion>
    <IntegerCode>1</IntegerCode>
    <SourceA>return value</SourceA>
    <SourceB>another value</SourceB>
  </Conversion>
  ....

From here it's easy to modify the XPath expression in the StringLookup method.

Private Function StringLookup(ByVal MyInteger As Integer, ByVal ElementName As String) As String

    Dim xdoc As New XPathDocument("Components\IntLookup.xml")
    Dim nav As XPathNavigator = xdoc.CreateNavigator()
    Dim iterator As XPathNodeIterator = _
        nav.Select(String.Format("//IntegerCode[.'{0}']/parent::node()/{1}", MyInteger, ElementName))
    iterator.MoveNext()

    Return iterator.Current.Value
End Function