_editor.StartEditing(_workspace);
You don't need permissions on all the featureclasses to start an edit session on the workspace. You do need permissions on some of them of course. Can you start the edit through the ArcMap interface? Do you have versioning on the featureclasses? Is the editor set to do edit with do/undo? Do you have some featureclasses loaded in some layers in the map that have edit permissions? Can you re-run the grant edit on the featureclasses you need to edit?
private void startEditing() { //get the workspace necessary for editing _workspace = getWorkspace(); //get the Editor singleton object and start editing getEditor(); if (_editor.EditState == esriEditState.esriStateNotEditing) { try { _editor.StartEditing(_workspace); } catch (Exception e) { MessageBox.Show(e.Message); } } } private void getEditor() { IUID _ID = new UIDClass(); _ID.Value = "esriEditor.Editor"; _editor = ArcMap.Application.FindExtensionByName("ESRI Object Editor") as IEditor2; } public IWorkspace getWorkspace() { IWorkspaceFactory2 _wsf; IWorkspace _WS; string _server = ""; try { _server = "ServerName"; _wsf = new SdeWorkspaceFactoryClass(); IPropertySet _ps = new PropertySetClass(); _ps.SetProperty("SERVER", _server); _ps.SetProperty("INSTANCE", "5151"); _ps.SetProperty("DATABASE", ""); _ps.SetProperty("USER", "username"); _ps.SetProperty("PASSWORD", "password"); _ps.SetProperty("AUTHENTICATION_MODE", "DBMS"); _ps.SetProperty("VERSION", "SDE.DEFAULT"); _WS = _wsf.Open(_ps, 0); return _WS; } catch (Exception) { return null; } }