Error When Binding DropDown List from DataBase

Hi,

I am using a dropdown list in gridview and populating it from database.However ,i am getting "object reference not set to an instance ..." error even though i have reference.

I have two more similar drop down list and they are working perfectly.

I am uploading the options for the dropdownlist from a "tab delimited" text file for all the dropdown list.

I am not getting where exactly the problem is.

please help me solve this.

                <asp:TemplateField HeaderText="Property" HeaderStyle-Wrap="false">
                    <ItemTemplate>
                    <asp:Label ID="lblProperty" runat="server"  Text='<%#Eval("Property")%>'></asp:Label>
                       
                    </ItemTemplate>
                    <EditItemTemplate>                 
                        <asp:Label ID="lblProperty" runat="server" Visible="false" Text='<%#Eval("Property") %>'></asp:Label>
                        <asp:DropDownList ID="ddlPropertyEdit" runat="server"></asp:DropDownList>

                    </EditItemTemplate>
                    <FooterTemplate>
                     <asp:DropDownList ID="ddlPropertyFoot" runat="server">
                        </asp:DropDownList>
                    </FooterTemplate>

<HeaderStyle Wrap="True"></HeaderStyle>
                </asp:TemplateField>

                             ddlProperty = new DropDownList();
                             ddlProperty = (DropDownList)e.Row.FindControl("ddlPropertyEdit");
                             GridSource = new DataSet();
                             GridSource = BusinessObj.GridBind(SelectedMonth, "Property");// Get the values from database.

                             ddlProperty.DataSource = GridSource;
                             ddlProperty.DataTextField = "Property";
                             ddlProperty.DataValueField = "Property";
                             ddlProperty.DataBind();                            
                             ddlProperty.Items.Insert(0, new ListItem("-Select Property-", "0"));
                             ddlProperty.Items.FindControl((e.Row.FindControl("lblProperty") as Label).Text).Selected=true;