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4GuysFromRolla.com : ASP FAQS : Arrays

Question: How can I determine the position of a particular string in an Array?

Answer: A very simple way of determining whether or not a string exists in an array is to use a loop, checking each element:

Dim iLoop, iPos
iPos = -1

For iLoop = LBound(SomeArray) to UBound(SomeArray)
  If CStr(SomeString) = CStr(SomeArray(iLoop)) then
    'We found the element
    iPos = iLoop
  End If
Next

At this point, iPos will equal the position that SomeString was found in SomeArray, or, if the string was not found in the array, iPos will equal -1.

While the above code is satisfactory, why not encapsulate it in a function so that we can easily reuse it? Also, another potential problem: how are we wanting to compare the string value to the elements in the array? If we are looking for the string "FooBar" in an array, are we content if we find "Foobar", or do we care about the case?

With that being said, I propose the following function be used to quickly determine the position an element exists in an array:

Function PositionInArray(aMyArray, strLookingFor, compare)
'Return the position strLookingFor is found in aMyArray... if
'strLookingFor is not found, -1 is returned.

  Dim iUpper, iLoop
  iUpper = UBound(aMyArray)

  For iLoop = LBound(aMyArray) to iUpper
    If compare = vbTextCompare then
      If CStr(UCase(aMyArray(iLoop))) = CStr(UCase(strLookingFor)) then
        PositionInArray = iLoop
        Exit Function
      End If
    Else
      If CStr(aMyArray(iLoop)) = CStr(strLookingFor) then
        PositionInArray = iLoop
        Exit Function
      End If
    End If
  Next

  'Didn't find the element in the array...
  PositionInArray = -1

End Function

Note that our function expects three parameters: aMyArray, the string array that we are searching; strLookingFor, the string that we are looking for in the array aMyArray; and compare, which indicates if we are wanting to do a case-sensitive search (vbBinaryCompare) or a case-insensitive search (vbTextCompare).

Here is an example program for which the above function can be used:

<%
  '******* INCLUDE ABOVE FUNCTION IN CODE HERE **********

  Dim aSomeArray
  aSomeArray = Array("I", "think", "ASP", "is", "cool!")

  Response.Write PositionInArray(aSomeArray, "I", vbBinaryCompare) & "<BR>"
  Response.Write PositionInArray(aSomeArray, "foo", vbBinaryCompare) & "<BR>"
  Response.Write PositionInArray(aSomeArray, "ASP", vbBinaryCompare) & "<BR>"
  Response.Write PositionInArray(aSomeArray, "bar", vbBinaryCompare) & "<BR>"
  Response.Write PositionInArray(aSomeArray, "Cool!", vbTextCompare) & "<BR>"
%>

Output is:
0
-1
2
-1
4


Happy Programming!


FAQ posted by Scott Mitchell at 11/26/2000 2:11:12 PM to the Arrays category. This FAQ has been viewed 58,403 times.


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