async public void Content_DragDrop(DragEventArgs e, IUserData userdata)
        {
            if (_fdb == null)
            {
                return;
            }

            bool schemaOnly = false;

            if (userdata != null &&
                userdata.GetUserData("gView.Framework.UI.BaseTools.PasteSchema") != null &&
                userdata.GetUserData("gView.Framework.UI.BaseTools.PasteSchema").Equals(true))
            {
                schemaOnly = true;
            }

            if (e.Data.GetDataPresent(DataFormats.FileDrop))
            {
            }
            else
            {
                foreach (string format in e.Data.GetFormats())
                {
                    object ob = e.Data.GetData(format);
                    if (ob is IEnumerable <IExplorerObjectSerialization> )
                    {
                        ExplorerObjectManager exObjectManager = new ExplorerObjectManager();

                        List <IExplorerObject> exObjects = new List <IExplorerObject>(await exObjectManager.DeserializeExplorerObject((IEnumerable <IExplorerObjectSerialization>)ob));
                        if (exObjects == null)
                        {
                            return;
                        }

                        foreach (IExplorerObject exObject in ListOperations <IExplorerObject> .Clone(exObjects))
                        {
                            IFeatureClass fc = await exObject?.GetInstanceAsync() as IFeatureClass;

                            if (fc == null)
                            {
                                continue;
                            }

                            if (fc.Dataset != null && fc.Dataset.DatasetName == _dsname &&
                                _fdb != null &&
                                fc.Dataset.Database is AccessFDB &&
                                ((AccessFDB)fc.Dataset.Database)._conn.ConnectionString.ToLower() ==
                                _fdb._conn.ConnectionString.ToLower())
                            {
                                exObjects.Remove(exObject);
                            }
                        }
                        if (exObjects.Count == 0)
                        {
                            return;
                        }

                        FormFeatureclassCopy dlg = await FormFeatureclassCopy.Create(exObjects, _dataset);

                        dlg.SchemaOnly = schemaOnly;
                        if (dlg.ShowDialog() != DialogResult.OK)
                        {
                            continue;
                        }

                        foreach (FeatureClassListViewItem fcItem in dlg.FeatureClassItems)
                        {
                            await ImportDatasetObject(fcItem, schemaOnly);
                        }

                        /*
                         * foreach (IExplorerObject exObject in exObjects)
                         * {
                         *  ImportDatasetObject(exObject.Object);
                         * }
                         * */
                        exObjectManager.Dispose(); // alle ExplorerObjects wieder löschen...
                    }
                }
            }
            await _dataset.RefreshClasses();

            await this.Refresh();
        }