Using the following example project for a multi-select in a Grid:
- Run the project as-is.
- Edit any grid line.
- Add a Territory by typing the first few letters and pressing enter to select the highlighted item.
- Save the grid line
In the Update action, the ModelState is not valid and the Territories list in the EmployeeViewModel has null entries for the first X items (equivalent the the number of items existing before the update). The data POSTed from the grid seems to be inconsistent. New items are posted as TerritoryViewModel-type objects but the existing items are posted as the value (id) only.
Adding at least one item by clicking with the mouse magically resolves this issue and all items are posted as complete objects.