Sqldatasource inside gridview

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C#

ASP.NET

Gridview

SqlDataSource

or the past days i've been trying to find a solution for my problem but so far i couldn't. I Have a Gridview that in edit mode, one of the fields have a DropDownList of people that is populated by a Select that uses two other fields of that row (State and City). I tried everything i found on the web about it and i couldn't make it work. Can you help me please? Code below

<asp:GridView ID="GridView1" runat="server" AllowSorting="True"  
        DataKeyNames="id,Municipio,UF" DataSourceID="SqlDataSource5">
        <AlternatingRowStyle BackColor="White" />
        <Columns>
            <asp:CommandField ShowEditButton="True" />
            ...stuff...
            <asp:TemplateField HeaderText="UF" SortExpression="UF">
                <EditItemTemplate>
                    <asp:Label ID="Label1" runat="server" Text='<%# Eval("UF") %>'>
                    </asp:Label>
                </EditItemTemplate>
                <ItemTemplate>
                    <asp:Label ID="Label1" runat="server" Text='<%# Bind("UF") %>'>
                    </asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Municipio" SortExpression="Municipio">
                <EditItemTemplate>
                    <asp:Label ID="Label2" runat="server" Text='<%# Eval("Municipio") %>'></asp:Label>
                </EditItemTemplate>
                <ItemTemplate>
                    <asp:Label ID="Label2" runat="server" Text='<%# Bind("Municipio") %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="People" SortExpression="People">
                <ItemTemplate>
                    <asp:Label ID="LbPeople" runat="server" Text='<%# Bind("Cultura") %>'></asp:Label>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:DropDownList ID="DdlPeople" runat="server" AutoPostBack="true" 
                        DataSourceID="SqlDataSourcePeopleEdit" DataTextField="People" 
                        DataValueField="People">
                    </asp:DropDownList>
                    <asp:HiddenField ID="Hidden1" Value='<%# Bind("Municipio") %>' runat="server"/>
                    <asp:HiddenField ID="Hidden2" Value='<%# Bind("UF") %>' runat="server"/>
                    <asp:SqlDataSource ID="SqlDataSourcePeopleEdit" runat="server" 
                        ConnectionString="<%$ ConnectionStrings:dbdb %>" 
                        ProviderName="<%$ ConnectionStrings:somar.ProviderName %>"
                        SelectCommand="SELECT People FROM Table_People WHERE (Cidade = @Municipio) AND (UF = @UF)"
                        CancelSelectOnNullParameter="false">
                        <SelectParameters>
                            <asp:ControlParameter ControlID="Hidden1" Name="Municipio" PropertyName="Value" Type="String" />
                            <asp:ControlParameter ControlID="Hidden2" Name="UF"        PropertyName="Value" Type="String" />
                        </SelectParameters>
                    </asp:SqlDataSource>
                </EditItemTemplate>
            </asp:TemplateField>
       ...stuff...     
    </asp:GridView>

What am i doing wrong?

What I have tried:

When i click edit, the dropdownlist does not load values. And if i set the property CancelSelectOnNullParameter="false" on SqlDataSource it shows 'Must declare scalar variable @xxx' I have inspected the hiddenfields and they have values loaded, so the problem is the controlparameter taht does not get the value from it