How to search through all items in a list

Hi,

So I've been making a new Change Management system for our organisation.

At one stage the user needs to enter in what Configuration Items are affected by their change. This is done through a collection as the items are imported from a different database.

As the person adds each item, I then have a script that grabs the names of each one and puts it into a field (String -1) on the main window.

The items also come with a code to say what items they might affect.

I would like to have the script run a loop to go through each item in a list to see what matches that code so it can add it to the field on the main window.

I have tried with a reference list, however it doesn't seem to allow a loop to just search through each reference item for a match.

Here's an example of what I tried:

import System

static def GetAttributeevalue(Change):

txtCIID = " "

if Change._ConfigurationItems.Count == 0

  Value = String.Format("No Configuration Items Selected")

else:

  Value = String.Format("The following Configuration Items have been selected:\n\n")

  for item in Change._ConfigurationItems:

   txtCIID = item._CIID

   Value += String.Format("Configuration Items: {0}", item._Name)

   for record in Change._ImpactedCIs:

    if txtCIID == record._LINKTABLE1RECORDID:

     Value += String.Format("\n\tImpacted Configuration Item: {0}", record._CINAME1)

    Value += String.Format("\n\n")

return Value

This works fine if I don't include the part to check aginst the Change._ImpactedCIs reference list. When I do include it the error log returns the following line:

"Cannot enumerate null."

Any ideas?