Comparing 2 arrays and finding missing Items

//Gets a list of the items in an array missing from a second array.

using System.Collections;

public ArrayList GetMissingItems(string[] allItems, ArrayList someItems)
{
ArrayList missingItems = new ArrayList();
for (int i=0; i
{
if ( allItems[i].Trim().Length > 0 ) //filter out empty strings
{
if ( !someItems.Contains(allItems[i].Trim()) )
{
missingItems.Add(allItems[i]);
}
}
} return missingItems;
}