problem when I update an image file in gridview

[haina]

the aspx file as blow
<asp:DetailsView Width="100%" ID="dvOrg" runat="server" DataKeyNames="Id" AutoGenerateRows="False"
OnModeChanging="dvOrg_ModeChanging" OnItemUpdating="dvOrg_OnItemUpdating"
CellPadding="4" GridLines="None" >
<Fields>
<asp:TemplateField SortExpression="Logo" HeaderText="Logo:">
<ItemTemplate>
<asp:Image ID="imgLogo" runat="Server" Width="100px" Height="100px"
ImageUrl='<%# "~/data/OrganizationLogo/" + Eval("Id") + ".jpg" %>' />
</ItemTemplate>
<EditItemTemplate>
<asp:FileUpload ID="fuEditLogo" runat="server" />
200px*200px
</EditItemTemplate>
<asp:CommandField ShowEditButton="True" ValidationGroup="vgOrgEdit" InsertVisible="False">
<ItemStyle HorizontalAlign="Center" />
</asp:CommandField>
</Fields>
</asp:DetailsView>

I use organization id to set the image files name so the name will not change even the file has been update. After I update the image, the gridview still show the old image. I have to click refresh to see the new image.
I use blow code to avoid cache
protected void Page_Load(object sender, EventArgs e)
{
Response.ExpiresAbsolute = DateTime.Now.AddMinutes(-1);
Response.Expires = 0;
Response.CacheControl = "no-cache";
if (!IsPostBack)
{
Initialize();
}
}

I am sure the new image have been saved succussfully. Why it can not been seen at postback.
thank you