Here Mudassar Ahmed Khan has explained with an example, how to add (insert) Item in ComboBox after DataBind in Windows Forms Application using C# and VB.Net.
It is not possible to add (insert) Item in ComboBox after DataBind and hence first a DataTable will be populated from database and then the Item will be added to it, finally the ComboBox will be populated from DataTable in Windows Forms Application using C# and VB.Net.