private void btnRemoveSelectedSecurityGroups_Click(object sender, RoutedEventArgs e) {//set the selected items for the _viewModel _viewModel.SelectedAssignedSecurityGroupList = lbxAssignedSecurityGroups.SelectedItems; //do the required MenuSecurity CRUD _viewModel.RemoveSelectedSecurityGroupsCommand(); for (int j = lbxAssignedSecurityGroups.SelectedItems.Count - 1; j >= 0; j--) {//move item from one list to the other... SecurityGroup item = (SecurityGroup)lbxAssignedSecurityGroups.SelectedItems[j]; _viewModel.AssignedSecurityGroupList.Remove((SecurityGroup)item); _viewModel.AvailableSecurityGroupList.Add((SecurityGroup)item); } //need to remove from list and add to the other list... lbxAssignedSecurityGroups.SelectedItems.Clear(); }