asp EntityDataSource detailsview OnItemUpdating e.cancel - asp.net

Question

I will explain my problem.
So I have an asp page with 2 entityDataSource.
- The first one is used to fill my obout table:
<asp:EntityDataSource ID="EntityDataSource1" ContextTypeName="RichDataBusinessApplication.Web.RichDataEntities" EnableFlattening="false" EnableInsert="true"
EnableUpdate="true" EnableDelete="true" EntitySetName="UserInformations" runat="server" />
My obout table is in an updatepanel. When I want to edit a row in my table, this method is handled:
protected void Button_Command(object sender, CommandEventArgs e)
{
SelectedUserHiddenField.Value = e.CommandArgument.ToString();
UsersCustomerDetailsView.ChangeMode(DetailsViewMode.Edit);
OpenPopupDialog(String.Format("#{0}", UpdatePopupPanel.ClientID));
}
The function OpenPopupDialog open a jquery popup dialog with the informations of my user I can now edit:
<asp:Panel ID="UpdatePopupPanel" runat="server" CssClass="popup-dialog">
<asp:UpdatePanel runat="server" ID="UpdatePanel1" UpdateMode="Conditional">
<Triggers>
<asp:AsyncPostBackTrigger ControlID="UsersGrid" EventName="Select" />
</Triggers>
<ContentTemplate>
<asp:DetailsView runat="server" ID="UsersCustomerDetailsView" DataSourceID="SelectedUserDataSource2" DefaultMode="Edit" AutoGenerateEditButton="true" AutoGenerateRows="false"
OnItemUpdating="UserDetailsView_ItemUpdating" OnItemUpdated="UserDetailsView_ItemUpdated"
OnItemCommand="UserDetailsView_ItemCommand"
DataKeyNames="UserId" Width="100%">
<Fields>
<asp:TemplateField>
<HeaderTemplate>
<uc:CulturalLabel ID="CulturalLabel1" runat="server" Text="Lastname" />
</HeaderTemplate>
<EditItemTemplate>
<asp:TextBox ID="LNameTextBox" runat="server" Text='<%# Bind("Lastname") %>' CssClass="textEntry" ValidationGroup="CoordonneValidationGroupUp"/>
<asp:RequiredFieldValidator ID="CustomRequieredValidator2" runat="server" ControlToValidate="LNameTextBox" CssClass="failureNotification" ErrorMessage="test" ValidationGroup="CoordonneValidationGroupUp">*</asp:RequiredFieldValidator>
</EditItemTemplate>
</asp:TemplateField>
</Fields>
</asp:DetailsView>
</ContentTemplate>
</asp:UpdatePanel>
</asp:Panel>
The second EntityDataSource allow to fill the fields of my popup of my detailsview is this one:
<asp:EntityDataSource ID="SelectedUserDataSource2" ContextTypeName="RichDataBusinessApplication.Web.RichDataEntities" EnableFlattening="false" EnableInsert="true" EnableUpdate="true" EnableDelete="true" EntitySetName="UserInformations" runat="server" AutoGenerateWhereClause="True">
<WhereParameters>
<asp:ControlParameter Name="UserId" ControlID="SelectedUserHiddenField" DbType="Guid" PropertyName="value" />
</WhereParameters>
</asp:EntityDataSource>
When I clic on the update button of my popup I handled the "OnItemUpdating" of my detailsview:
protected void UserDetailsView_ItemUpdating(Object sender, DetailsViewUpdateEventArgs e){
Page.Validate("CoordonneValidationGroupUp");
if (Page.IsValid)
{
//code to execute if page is valid
}
else
{
e.cancel = true;
}
}
The problem is the following:
When my page is not valid because of the lastname is blank, "e.cancel=true" is executed but the "*" and error message don't appear and the field of my popup is reloaded with the data of the first row in my database.
So, if someone can help me!
Thanks!