Ext.Net 1.x_Ext.Net.CheckboxSelectionModel类型Ext.grid.GridPanel的某行不能选择

<SelectionModel>
<ext:CheckboxSelectionModel Visible="true" ID="UserCheck" runat="server" SelectedRecordID="Status">
<Listeners>
<BeforeRowSelect Fn="MyBeforeRowSelect" />
</Listeners>
</ext:CheckboxSelectionModel>
</SelectionModel>

var MyBeforeRowSelect = function (SelectionModel, rowIndex, keepExisting, record) {
if (record.get('Status') != "W") {
return false;
}
else {
return true;
}
}