I would like to know how to use the custom SPFieldType (Existing on the Site) when adding new SPList column.
E.g. [Normal way using the SPFieldType.Text field type]
list.Fields.Add("Location", SPFieldType.Text, true);
list.Update();
How about for the custom field type?
list.Fields.Add("Location", [Custom SPField Type], true); ?
Thanks in advance.
Instead of Add, try AddFieldAsXml.
For more information, see Programmatically creating a field (column) from the Custom field type.