GridView Fired RowEditing without handler but EditItemTemplate is on the GridView

<asp:GridView ID="gvwClassList" DataKeyNames="classID" Width="95%" AutoGenerateColumns="false" AutoGenerateEditButton="true" SkinID="JCB" runat="server">
<Columns>
    <asp:TemplateField HeaderText="Status">
        <ItemTemplate>
            <%# Eval("dimControlText")%>
        </ItemTemplate>
        <EditItemTemplate>
            <asp:DropDownList ID="ddlClassStatus" DataSourceID="sdsDimensionValues" DataTextField="dimControlText" DataValueField="dimID" SelectedValue='<%# Bind("dimID") %>' runat="server"></asp:DropDownList>
        </EditItemTemplate>
    </asp:TemplateField>
    <asp:BoundField DataField="classID" Visible="false" />
    <asp:BoundField DataField="courseName" HeaderText="Course Name" />
    <asp:BoundField DataField="startDate" HeaderText="From" DataFormatString="{0:d}" HtmlEncode="false" />
    <asp:BoundField DataField="endDate" HeaderText="To" DataFormatString="{0:d}" HtmlEncode="false" />
    <asp:BoundField DataField="instructorsName" HeaderText="Instructor" />
</Columns>
</asp:GridView>
 
<asp:SqlDataSource ID="sdsDimensionValues" ConnectionString="<%$ ConnectionStrings:dev %>" 
    SelectCommand="Select dimID, dimControlText From dbo.sys_dimValues Where dimCat = 'STATUS'" runat="server">
</asp:SqlDataSource>