Record not updating in detailsview

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ASP.NET

DetailsView

i want to update records of database using detailsview in asp.net . i have used the following code it runs well but at the end no record is updated i am not aware of the reason that why record is not updated as there is no error as for as i know code is as follow:

<asp:DetailsView ID="DetailsView1" runat="Server" CellPadding="4" ForeColor="#333333" GridLines="None"
     Width="100%" DataSourceID="SqlDataSource1" AllowPaging="True" AutoGenerateRows="False" DataKeyNames="QuestionID"
     AutoGenerateDeleteButton="True" AutoGenerateEditButton="True"
                    AutoGenerateInsertButton="True" DefaultMode="Edit" >
        <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
        <CommandRowStyle BackColor="#E2DED6" Font-Bold="True" />
        <EditRowStyle BackColor="#999999" />
        <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
        <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
        <FieldHeaderStyle BackColor="#E9ECF1" Font-Bold="True" />
        <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
        <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
        <Fields>
            <asp:TemplateField HeaderText="QuestionID">
                <ItemTemplate>
                    <%# Eval("QuestionID") %>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:BoundField DataField="Questiontext" HeaderText="Questiontext" />
            <asp:BoundField DataField="Helptext" HeaderText="Helptext" />
            <asp:BoundField DataField="Answertype" HeaderText="Answertype" />

        </Fields>
    </asp:DetailsView>

    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString='<%$ ConnectionStrings:ConnectionString %>'
       SelectCommand="Select * FROM Questions WHERE SurveyId=@sid"
       DeleteCommand="Delete FROM Questions WHERE QuestionID = @QID"
       UpdateCommand="UPDATE Questions SET Questiontext = @text, Helptext = @htext, Answertype = @atype WHERE QuestionID = @QID"
   >
        <DeleteParameters>
            <asp:Parameter Name="QID" Type="Int32" />
        </DeleteParameters>
        <UpdateParameters>
            <asp:Parameter Name="QID" Type="Int32" />
            <asp:Parameter Name="text" Type="string"  />
            <asp:Parameter Name="htext" Type="string" />
            <asp:Parameter Name="atype"  Type="string" />

         </UpdateParameters>
        <SelectParameters>
         <asp:QueryStringParameter  Name="sid" QueryStringField="SurveyId"/>
       </SelectParameters>
        </asp:SqlDataSource>

Sorry if there is some stupid type of error which i dont know as i am still a laerner in this field!