Object reference not set to an instance of an object.

Hi,


                I tried the datagrid cell editing. But i'm getting the following error. Error message is "Object reference not set to an instance of an object.". How to solve this error? Here i attached my code also.



<asp:TemplateColumn HeaderText="Appoinment Date">
                        <ItemTemplate>
                            <%#DataBinder.Eval(Container.DataItem, "followupdate")%>
                        </ItemTemplate>
...