Code
<asp:GridView ID="GridView1" runat="server" CellPadding="4"  DataKeyNames="id"
    ForeColor="#333333" GridLines="None" Width="797px" AutoGenerateColumns="False" 
        onrowdatabound="GridView1_RowDataBound" 
        onselectedindexchanged="GridView1_SelectedIndexChanged" 
        style="text-align: left" Height="194px" 
        onrowcommand="GridView1_RowCommand" onrowediting="GridView1_RowEditing" 
        onrowcancelingedit="GridView1_RowCancelingEdit" 
        onrowupdated="GridView1_RowUpdated" onrowupdating="GridView1_RowUpdating">
        <RowStyle BackColor="#E3EAEB" />
        <Columns>
            <asp:TemplateField HeaderText="任务名称">
                <EditItemTemplate>
                    <asp:TextBox ID="TextBox3" runat="server" Text='<%# Eval("taskName") %>'></asp:TextBox>
                </EditItemTemplate>
                <ItemTemplate>
                    <asp:HyperLink ID="HyperLink1" runat="server" 
                        NavigateUrl='<%# Eval("id", "taskDetails.aspx?id={0}") %>' 
                        Text='<%# Eval("taskName") %>'></asp:HyperLink>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="创建时间">
                <EditItemTemplate>
                    <asp:Label ID="Label2" runat="server" Text='<%# Bind("ct") %>'></asp:Label>
                </EditItemTemplate>
                <ItemTemplate>
                    <asp:Label ID="Label2" runat="server" Text='<%# Bind("ct") %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="状态">
                <EditItemTemplate>
                    <asp:Label ID="Label1" runat="server" Text='<%# Bind("taskStatus") %>'></asp:Label>
                </EditItemTemplate>
                <ItemTemplate>
                    <asp:Label ID="Label1" runat="server" Text='<%# Bind("taskStatus") %>'></asp:Label>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="操作">
                <EditItemTemplate>
                    <asp:LinkButton ID="LinkBtnUpdate" runat="server" CommandName="Update">更新</asp:LinkButton>
                    |<asp:LinkButton ID="LinkBtnCancle" runat="server" CommandName="Cancle" Text="取消"></asp:LinkButton>
                    &nbsp;
                </EditItemTemplate>
                <ItemTemplate>
                    <asp:LinkButton ID="LinkButtonEdit" runat="server" CommandName="Edit" 
                        >编辑任务</asp:LinkButton>
                    &nbsp;|
                    <asp:LinkButton ID="LinkBChangeStatus" runat="server" CommandName="changeStatus">改变状态</asp:LinkButton>
                    &nbsp;|
                    <asp:LinkButton ID="LinkButtonDelete" runat="server" CommandName="Delete" >删除</asp:LinkButton>
                    
                    &nbsp;
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
        <FooterStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />
        <PagerStyle BackColor="#666666" ForeColor="White" HorizontalAlign="Center" />
        <SelectedRowStyle BackColor="#C5BBAF" Font-Bold="True" ForeColor="#333333" />
        <HeaderStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />
        <EditRowStyle BackColor="#7C6F57" />
        <AlternatingRowStyle BackColor="White" />
    </asp:GridView>

Code
protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
        {
            //获取TextBox的值，即用户输入的值
            string newName = (GridView1.Rows[e.RowIndex].Cells[0].FindControl("TextBox3") as TextBox).Text;
            //获取id
            int taskID=Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Value);
            //进行更新
            dataAccess da = new dataAccess();
            if (da.EditTask(newName, taskID))
            {
                //提示更新成功
            }
            else 
            {
                //提示出错，更新失败
            }
        }