ObservableCollection<ModelDept> dept_observerlist = new ObservableCollection<ModelDept>();

        public void setFirst() {
            datagrid.SelectedIndex = 0;
            datagrid.ScrollIntoView(datagrid.SelectedItem);
            datagrid.Focus();
        }

        public void setPrev() {
            if (datagrid.SelectedIndex > 0) {
                datagrid.SelectedIndex = datagrid.SelectedIndex - 1;
                datagrid.ScrollIntoView(datagrid.SelectedItem);
                datagrid.Focus();
            }
        }

        public void setNext() {
            if (datagrid.SelectedIndex < (dept_observerlist.Count - 1)) {
                datagrid.SelectedIndex = datagrid.SelectedIndex + 1;
                datagrid.ScrollIntoView(datagrid.SelectedItem);
                datagrid.Focus();
            }
        }

        public void setLast() {
            datagrid.SelectedIndex = dept_observerlist.Count - 1;
            datagrid.ScrollIntoView(datagrid.SelectedItem);
            datagrid.Focus();
        }