<div class="alert alert-danger alert-error" style="display:none" id="alertErrorMessage">
<a href="#" class="close" data-dismiss="alert">×</a>
<strong>Error! </strong><% =HiddenField1.Value %>
</div>
<asp:HiddenField ID="HiddenField1" runat="server" Value="init HF value"/>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:GridView ID="gridViewAll" runat="server" CssClass="table table-striped table-hover table-bordered"
AutoGenerateColumns="False" DataKeyNames="ImageId"
OnRowEditing="gridViewStage_RowEditing"
...
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