编译器错误消息: CS0123: “gvUserList_pageIndexChanging”的重载均与委托“System.EventHandler”不匹配

前台代码：
 <asp:GridView runat="server" ID="gvUserList" AutoGenerateColumns="false" Width="100%"
                        AllowPaging="true" PageSize="5" OnPageIndexChanged="gvUserList_pageIndexChanging"
                        OnRowEditing="gvUserList_RowEditing" OnRowDeleting="gvUserList_RowDeleting">
                        <Columns>
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <input name="CheckboxGroup" type="checkbox" value='<%#Eval("userID") %>'>
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:BoundField DataField=" userid" HeaderText="编号" />
                            <asp:BoundField DataField="telephone" HeaderText="发送手机" />
                            <asp:BoundField DataField="sendtime" HeaderText="发送时间" />
                            <asp:BoundField DataField="email" HeaderText="邮箱地址" />
                            <asp:BoundField DataField="substance" HeaderText="内容" />
                            <asp:CommandField ShowEditButton="true" ShowDeleteButton="true" HeaderText="操作" />
                        </Columns>
                        <EmptyDataTemplate>
                            温馨提示：当前没任何记录哟！！
                        </EmptyDataTemplate>
                    </asp:GridView>
后台： protected void gvUserList_RowEditing(object sender, GridViewEditEventArgs e)
    {
        gvUserList.EditIndex = e.NewEditIndex;
        GridViewBind();
    }