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<body>
    <form id="form1" runat="server">
    <div >
        <asp:CheckBoxList ID="CheckBoxList1" runat="server" DataSourceID="SqlDataSource1" DataTextField="Nome" DataValueField="idServico">

        </asp:CheckBoxList>

        <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>" SelectCommand="SELECT * FROM [Servicos] WHERE idServico NOT IN (SELECT idServicoFK FROM OficinasHasServicos WHERE idOficinaFK=@idOficinaFK) ORDER BY [Nome]">
            <SelectParameters>
                <asp:SessionParameter Name="idOficinaFK" SessionField="id" />
            </SelectParameters>
        </asp:SqlDataSource>
        <asp:EntityDataSource ID="EntityDataSource1" runat="server">
        </asp:EntityDataSource>
        <asp:Button id="btn1" runat="server" text="test" OnClick="btn1_Click"/>
    </div>
        <div>
            <asp:Literal runat="server" ID="lit1"></asp:Literal>
        </div>
    </form>
</body>