Empty value in datagridview combobox dropdown for nullable type

Question

I have a nullable enum binding to a combobox cell. The comboxbox style is set to dropdown.

Since my enum is nullable, I am expecting the Dropdown to have an empty value, but that doesn't seem to be the case.

Is there any built-in way of enforcing this, other than adding a "NULL" value to the enum and keeping track of that?

Answer 1

As far as I know, Windows Forms binding doesn't have anything like the WPF TargetNullValue property, so the only possible way is to handle the Format and Parse events:

Binding binding = new Binding // ..
comboBox.DataBindings.Add(binding);

binding.Format += (sender, eventArgs) =>
{
    if (eventArgs.Value == null)
        eventArgs.Value = "NULL";
    else
        eventArgs.Value = eventArgs.Value.ToString();
}

binding.Parse += (sender, eventArgs) =>
{
    if (eventArgs.Value == "NULL")
        eventArgs.Value = null;
    else
        eventArgs.Value = Enum.Parse(typeof(MyEnum), eventArgs.Value.ToString());
}