Why can't I select a null value in a ComboBox?

Question

In WPF, it seems to be impossible to select (with the mouse) a \"null\" value from a ComboBox. Edit To clarify, this is .NET 3.5 SP1.

Here\'s some c

Answer 1

this might not address your answer completely, but hopefully its a hit in the right direction:

1. Have you installed SP1?

From Scott Gu's Blog:

• NET 3.5 SP1 includes several data binding and editing improvements to
  WPF. These include:
• StringFormat support within {{ Binding }} expressions to enable easy formatting of bound values
• New alternating rows support within controls derived from ItemsControl, which makes it easier to set alternating properties on rows (for example: alternating background colors)
• Better handling and conversion support for null values in editable controls Item-level validation that applies validation rules to an entire bound item
• MultiSelector support to handle multi-selection and bulk editing scenarios
• IEditableCollectionView support to interface data controls to data sources and enable editing/adding/removing items in a transactional way
• Performance improvements when binding to IEnumerable data sources

Sorry if I wasted your time and this was not even close..but I think the problem is inherited from:

constraints of the strongly typed dataset

NullValueDataSet Explained here

But now the SP1 for .Net 3.5 should have addressed this issue..