DEVEXPRESS Use Cascade Combobox in İnline Edit Mode

<dx:GridViewDataComboBoxColumn FieldName="Category1ID" VisibleIndex="4">
                    <PropertiesComboBox DataSourceID="dsCategory1" TextField="Name" ValueField="ID" ValueType="System.Int32">
                    </PropertiesComboBox>
                    <EditItemTemplate>
                            <dxe:ASPxComboBox ID="Cat1" runat="server"
                            DataSourceID="dsCategory1"  TextField="Name" ValueField="ID" Value='<%# Bind("Category1ID") %>'
                            AutoPostBack="true" OnSelectedIndexChanged="Cat1_SelectedIndexChanged" ValueType="System.Int32">
                            </dxe:ASPxComboBox>
                    </EditItemTemplate>
                </dx:GridViewDataComboBoxColumn>

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protected void grid_HtmlRowCreated(object sender, DevExpress.Web.ASPxGridView.ASPxGridViewTableRowEventArgs e)
        {
            if ((e.RowType == GridViewRowType.InlineEdit)) {
                ASPxComboBox combo2 = ((ASPxComboBox)grid.FindEditRowCellTemplateControl(
                    grid.Columns["Category2ID"] as GridViewDataComboBoxColumn, "Cat2"));
                if (Request.Params[combo2.UniqueID] != null) return;

                if (!grid.IsNewRowEditing) {
                    object[] vals = (object[])grid.GetRowValues(grid.EditingRowVisibleIndex,
                    new string[] { "Category2ID", "Category3ID", "Category4ID" });
                    ASPxComboBox combo4 = ((ASPxComboBox)grid.FindEditRowCellTemplateControl(
                    grid.Columns["Category4ID"] as GridViewDataComboBoxColumn, "Cat4"));
                    ASPxComboBox combo3 = ((ASPxComboBox)grid.FindEditRowCellTemplateControl(
                    grid.Columns["Category3ID"] as GridViewDataComboBoxColumn, "Cat3"));
                    combo2.Value = vals[0];
                    combo3.Value = vals[1];
                    combo4.Value = vals[2];
                }
            }
        }