How to bind a drop-down list in GridView with the Form Designer

Adding a GridView to the Form Designer and using a drop-down list in one of the columns bound from a database source/table causes the following .NET error when loading the form at runtime:

[FIELD] has a SelectedValue which is invalid because it does not exist in the list of items.  Parameter name: value

This is because the drop-down list default is a String.Empty value, and so it cannot find a valid item with an empty value in the drop-down list, since it is bound to a database table that doesn’t contain a record of which value column has a String.Empty value.

The solution is to define a static default item in the drop-down list. To do this:

  1. In the Form Designer, click the pencil icon next to the drop-down list to open the Settings window.

  2. On the Items tab, add a static default item with the value="" (without blank spaces) and Text="Select..."

  3. On the Databind tab, check the Append data bound items option.