Gets the ObjectID of the active row in the table. The value of the row can be null, when the table does not have object ids, the active row is the new row, or the data for the row has not been loaded.

public Nullable<long> ActiveObjectId {get;}

Public ReadOnly Property ActiveObjectId As Nullable(Of Long)

//Get the active table view.
var tableView = TableView.Active;
if (tableView == null)
  return;

// get the active objectID
long? OID = tableView.ActiveObjectId;