GridPanel.ColumnModel.Columns.Count=0 if add columns at runtime to Grid so cannot get editor field at runtime

[vinhpt]

I want to create the GridPanel that add columns with editor at the run time but. Please help!

//design

<ext:GridPanel ID="gridThietHai" runat="server" >
        <Store>
            <ext:Store ID="storeThietHai" runat="server">
                <Reader>
                    <ext:JsonReader />
                </Reader>
            </ext:Store>
        </Store>
        <ColumnModel ID="mcolThietHai">
        </ColumnModel>
        <SelectionModel>
                        <ext:RowSelectionModel ID="smodeThietHai" SingleSelect="true">
                        </ext:RowSelectionModel>
                    </SelectionModel>
                    <Plugins>
                        <ext:RowEditor ID="editorThietHai" runat="server">
                            <DirectEvents>
                                <AfterEdit OnEvent="editorThietHai_DirectAfterEdit" />
                            </DirectEvents>
                        </ext:RowEditor>
                    </Plugins>
    </ext:GridPanel>

//code behide

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!Ext.Net.X.IsAjaxRequest)
            {

            Ext.Net.Store storeMain = gridThietHai.GetStore();
            Ext.Net.DataReader reader = storeMain.Reader[0];
            Ext.Net.Column column;
            
            Ext.Net.Field fld;
            string colName="TEST";
            reader.Fields.Add(colName);
                    
            column=new Ext.Net.Column();
            column.ColumnID = colName;
            column.Header = colName;
            column.DataIndex = colName;

            fld = new Ext.Net.TextField();
            column.Editor.Add(fld);
                    
            grid.ColumnModel.Columns.Add(column);

            //already do binding data for grid

            }
        }

protected void editorThietHai_DirectAfterEdit(object sender, Ext.Net.DirectEventArgs e)
        {
            Ext.Net.Field fld;
            foreach (Ext.Net.Column col in gridThietHai.ColumnModel.Columns){
                    fld = col.Editor.Editor;
//do stm here but gridThietHai.ColumnModel.Columns.Count=0 here so I cannot get the editor of the column at runtime. Please help
           }
}