未为gridivew.DataSource设置DataView对象引用作为DataView

Question

我有方法validatingeditor来验证重复项

private void GridView1_ValidatingEditor(object sender, DevExpress.XtraEditors.Controls.BaseContainerValidateEditorEventArgs e)
        {
            GridView view = sender as GridView;
            DataView currentDataView = view.DataSource as DataView;
            if (view.FocusedColumn.FieldName == "Sequence")
            {
                //check duplicate code  
                string currentCode = e.Value.ToString();
                for (int i = 0; i < currentDataView.Count; i++)
                {
                    if (i != view.GetDataSourceRowIndex(view.FocusedRowHandle))
                    {
                        if (currentDataView[i]["Sequence"].ToString() == currentCode)
                        {
                            e.ErrorText = "Duplicate Code detected.";
                            e.Valid = false;
                            break;
                        }
                    }
                }
            }
        }

但是它表示未设置对象引用，问题出在DataView currentDataView = view.DataSource as DataView;但是我不明白为什么。