C# WinForms - filtering one combobox based on the value of another combobox in a databound datagridview

Question

I have 4 tables - Agents, Customers, Counties and Towns. Agents and Customers both have a Town field and a County field. I have a DataGridView for each table. These are working

Answer 1

How is your data bound? If you use a DataView you can specify the RowFilter property and then refresh the underlying data. The rowfilter property works like a where clause and only returns a subset of the actual data.

A little background on DataView