Question

I have the following structure

|-Table 1
|--PK IDT1
|--Name field
|-Table 2
|--PK ID
|--FK IDT1
|--Name field

I want to bind Table 1 to combobox1 and Table 2 to combobox2 so as when someone selects a value in combobox1, combobox2 populates with only the rows with the FK IDT1 value from combobox1. Is this possible with databinding or do I have to code it?

Answer 1

on the FORM_LOAD of your application just populate only ComboBox1. this psuedocode may help you:

ON FORM_LOAD of your Application:

      Bind ComboBox1
      SET DISPLAY MEMBER Property of BomboBox1 to field
      SET VALUE MEMBER Property of ComboBox1 to IDT1
      Clear ComboBox1 current Text

On the SelectionChangeCommitted of your ComboBox1

      Bind ComboBox2 using the following Query:
           SELECT ID, field FROM Table2 WHERE IDT1 = ComboBox1.SelectedValue.ToString
      SET DISPLAY MEMBER Property of ComboBox2 to field
      SET VALUE MEMBER Property of ComboBox2 to IDT

The SelectedIndexChanged event is raised every time the SelectedIndex property value changes. If your ComboBox is initially empty then its SelectedIndex is -1. When you bind data to it the first item is selected by default and the SelectedIndex changes to 0. You are then explicitly setting the SelectedIndex to -1 again.

If you’re only interested in knowing when the user makes a selection then handle the SelectionChangeCommitted event instead.