Michel,

If you're asking what I think you're asking (searching an ADO.NET datatable for something)...

If you've defined a primary key, you can perform an ADO.NET FIND, which is (more or less) the equivalent of a SEEK.

If you need to do something beyond that, you can perform a ROWFILTER to create a view/get a collection of rows that match a condition.

Let me know if that helps...if it doesn't, if you can be a little more specific as to what types of lookups you want to do, maybe we can go from there.

Kevin