i am getting an chart error: chart element already exists

Question

my chart code

<asp:Chart ID="Chart3" runat="server" Height="316px" align="left"
                                  Width="431px"  >

                                <Series>
                                       <asp:Series Name="Series3" ChartType="Pie"   IsValueShownAsLabel="True"
                                        Font="Microsoft Sans Serif, 8pt, style=Bold"
                                        LabelBorderWidth="2" YValuesPerPoint="1" ChartArea="ChartArea1"
                                        Legend="Default"  LegendToolTip="#VAL( #PERCENT{P})" LabelToolTip="#VALX"
                                           Label="#TOTAL">
                                       </asp:Series>


                                       </Series>

                                       <ChartAreas >
                                           <asp:ChartArea Name="ChartArea1">
                                               <Area3DStyle Enable3D="True" />
                                               <Area3DStyle Enable3D="True"></Area3DStyle>
                                           </asp:ChartArea>
                                       </ChartAreas>
                                         <legends>
                                             <asp:Legend Alignment="Center" Name="Default" TableStyle="Wide"
                                                 TitleSeparator="DoubleLine" Title="Scheme"
                                                 TitleFont="Microsoft Sans Serif, 10pt, style=Bold" TitleForeColor="Blue">
                                             </asp:Legend>

                                         </legends>

                                   </asp:Chart>

 and my code behind is throwing an error at

this.Chart3.Legends.Add("Default");

 its saying the chart element 'default' already exists in legendcollection