Many thanks for your help - now it works as expected.
But I'm still a bit confused. The documentation
does not say that the type of field the 'dataValueField' points to has to be a string. Also the example provided there uses a number field.
Just for clarification: Does that means the DropDownList can only bound to string type fields?
Because I want the field in the Grid's data to be a boolean and not string type I added a DataSource that converts the type via model configuration - seems to work fine. The updated JS Bin
sample is here.