How can I convert anonymous type to strong type in LINQ?

Question

I have an array of ListViewItems ( ListViewItem[] ), where I store a SalesOrderMaster object in each ListViewItem.Tag for later reference.

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Answer 1

The part in that code that is expensive is calling the Contains method on the list. As it's an O(n) operation it gets slower the more objects you add to the list.

Just use a HashSet for the objects instead of a List. The Contains method of the HashSet is an O(1) operation, so your loop will be an O(n) operation instead of an O(n*n) operation.