Either create a custom object or get the textfield value as '1 - ABCD' from query itself.
For now, it looks like you are a beginner, try the Query way. When fetching the data, concatenate the ID and Text field and then use this field as the datatextfield while binding.
ID, TextF, (ID + '-' + TextF) AS IDTEXTF
mydropdown.Datasource = myFetchedDataTable;
mydropdown.DataValueField = "ID";
mydropdown.DataTextField = "IDTEXTF";