How to check exist object name in gridpanel list object in code behind or javascript?

[tuananhdnx]

Hi
Please give me an example how to check exist object in my gridpanel
I have a grid with a store

<ext:Store ID="Store1" 
      runat="server" 
                            OnBeforeStoreChanged="Store1_BeforeChanged" 
                            OnAfterStoreChanged="Store1_AfterChanged"
                            OnBeforeRecordInserted="Store1_BeforeInserted"
                            OnBeforeRecordUpdated="Store1_BeforeUpdated"
                            OnBeforeRecordDeleted="Store1_BeforeDeleted"
                            OnRefreshData="Store1_RefreshData"
                            >
                                   
                            <Reader>
                                <ext:JsonReader>
                                    <Fields>
                                        <ext:RecordField Name="ProvinceID" Type="String" />
                                        <ext:RecordField Name="ProvinceName" Type="String" />
                                    </Fields>
                                </ext:JsonReader>
                            </Reader>
                      </ext:Store>
                    </Store>

with ColumnModel

<ColumnModel ID="ColumnModel1" runat="server">
                        <Columns>
                            <ext:Column DataIndex="ProvinceID" Header="Ký hiệu" Width="100" >
                                <Editor>
                                    <ext:NumberField ID="NumberField1" runat="server" AllowBlank="false" AllowDecimals="true" AllowNegative="false">
                                    </ext:NumberField> 
                                </Editor>
                            </ext:Column>
                            <ext:Column DataIndex="ProvinceName" Header="Tên tỉnh" Width="200">
                                <Editor>
                                    <ext:TextField ID="TextField2" runat="server" AllowBlank="false" />
                                </Editor>
                            </ext:Column>
                        </Columns>
                    </ColumnModel>

I have already done inserte, update, delete data record on my gridpanel directly and have a Save button to Saves All Change. But validator doesn't work. For example, when i insert new record, validator focus cell error, but when i click Save button, record has been added to database without error message.
Second: I want check if ProvinceName exist in db, show a message or something to alert and stop saving. Can i check it on client side?
Thanks for help!