ASP.NET

OleDbCommand cmd = new OleDbCommand();
cmd.CommandText = "INSERT INTO tblCategory(CategoryName, OrderNum) " +
                  "VALUES(@CategoryName, @OrderNum) " +
                  "SELECT @@IDENTITY AS ID";
cmd.Parameters.Add(new OleDbParameter("@CategoryName", Category.CategoryName));
cmd.Parameters.Add(new OleDbParameter("@OrderNum", Category.Order));
cmd.Connection = DataAccess.CreateConnection("Malasot", false);
DataTable dt = new DataTable();
OleDbDataAdapter adapter = new OleDbDataAdapter(cmd);

if(cmd.Connection.State != ConnectionState.Open)
   cmd.Connection.Open();

adapter.Fill(dt); // ***the exception occurs here.***

<asp:button id="button1" runat="server" text="button1" />
<asp:upddatepanel id="upddatepanel1" runat="server">
<triggers>
<asp:asyncpostbacktrigger ControlID="button1" EventName="Click" />
</triggers>
</asp:upddatepanel>
<asp:UpdateProgress ID="ModalUpdateProgress1" DisplayAfter="0"
        runat="server" AssociatedUpdatePanelID="upddatepanel1">
 <ProgressTemplate>
     Loading ...
 </ProgressTemplate>
</asp:UpdateProgress>