If only specific export formats should be available for the end user, the list of formats can be restricted exactly to these formats. This is possible with the option LlOptionString.Exports_Allowed. A list of all available formats can be found in section Export.
ListLabel LL = new
ListLabel();
LL.DataSource = CreateDataSet();
// Only allow PDF and preview
LL.Core.LlSetOptionString(LlOptionString.Exports_Allowed, "PDF;PRV");
LL.Print();
LL.Dispose();