DropDownList inside GridView EditItemTemplate updates NULL values when using SqlDataSource UpdateCommand in ASP.Net

On update the dropdown value shows NULL in database : here's structure for my gridview 

<asp:TemplateField HeaderText="Construction Phase" SortExpression="Phase_Name">
                                                               <EditItemTemplate>
                                                                   <asp:DropDownList ID="EditedDropDownInGrid" runat="server" CssClass="form-control" DataSourceID="PhaseSQLDataSource" DataTextField="pp_name" DataValueField="pp_id">
                                                                   </asp:DropDownList>
                                                               </EditItemTemplate>
                                                               <ItemTemplate>
                                                                   <asp:Label ID="Label3" runat="server" Text='<%# Bind("Phase_Name") %>'></asp:Label>
                                                               </ItemTemplate>
                                                           </asp:TemplateField>

<asp:SqlDataSource ID="ExistingSqlSource" runat="server" ConnectionString="<%$ ConnectionStrings:BSDConnectionString %>"
                                                                      deletecommand="UPDATE [dbo].[d_activity] SET [act_dell] = 1, [act_dell_date] = GETDATE(), [act_deletedBy_Prefix] = @DelPrefix WHERE [act_id] = @act_id"
                                                                      UpdateCommand ="UPDATE [dbo].[d_activity] SET  act_pp_id = @Phase_Name , act_name = @Act_Name , act_lastupdateby = @lastUpdateBy , act_lastupdatedate = GetDate(), act_lastUpdateBy_Prefix = @lastUpdatePrefix WHERE act_id = @act_id"
                                                       >
                                                        
                                                       <deleteparameters>
                                                           <asp:SessionParameter  Name="DelPrefix" SessionField="Prefix" />
                                                           <asp:parameter name="act_id"  type="Int32" />
                                                       </deleteparameters>
 
                                                       
                                                       <UpdateParameters>
                                                           <asp:SessionParameter Name="lastUpdateBy" SessionField="LogInID" />
                                                           <asp:SessionParameter SessionField="Prefix" Name="lastUpdatePrefix" />
                                                           <asp:Parameter Name="Phase_Name"  type="Int32"/>
                                                           <asp:Parameter Name="Act_Name" Type="String" />
                                                           <asp:parameter name="act_id"  type="Int32" />
                                                       </UpdateParameters>
 
                                                   </asp:SqlDataSource>

it updates other controls in gridview but does not update my selected dropdowns item value in Integer format which is inside gridview