使用 BasePage 来解决 GridView 执行 RenderControl 产生的错误
手动解决 RenderControl 所产生的问题
下面的 ControlToHTML 函式,主要是将控件转换为对应的 HTML 程序代码。
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你可以整个 GridView 控件传入 ControlToHTML 来取得它的 HTML 程序代码,不过当执行此方法时,会遇到由 Page.VerifyRenderingInServerForm 方法释出的错误讯息。
当执行下面的程序代码时
Dim sHTML As String = ControlToHTML(GridView1)
会产生错误讯息
型别 'GridView' 的控件 'GridView1' 必须置于有 runat=server 的窗体标记之中。
要解决这个问题就是让 Page 不要执行 VerifyRenderingInServerForm 方法,所以 Page 要覆写 VerifyRenderingInServerForm 方法,而不做任何事。
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接下来继续执行程序,若 GridView 有 CommandFIeld 或分页时,它会去做事件验证的动作,而会引发另一个错误讯息
RegisterForEventValidation 只能在 Render(); 期间呼叫
要解决这个问题,可以切换到 aspx 程序代码中,在 <%@ Page %> 中加入 EnableEventValidation="false" 即可。
<%@ Page Language="VB" AutoEventWireup="false" EnableEventValidation="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>
使用 BasePage 解决 RenderControl 所产生的问题
虽然上述的方式可以解决 RenderControl 产生的问题,可是似乎有点太麻烦,有没有更简单的方式呢?我们用 BasePage 来处理这个问题,不用当有这类需求时还要去手动故这些设定。
TBBasePage 继承 Page,新增一个 IsVerifyRender 属性(预设为 True),来决定是否执行
MyBase.VerifyRenderingInServerForm 方法。首先覆写 VerifyRenderingInServerForm
方法,当 IsVerifyRender="False" 时,不会去执行 MyBase.VerifyRenderingInServerForm
方法;另外覆写 EnableEventValidation 方法,当 IsVerifyRender="False" 则传回
False。当我们要用 RenderControl 来输出控件的 HTML 码时,只需先设定 IsVerifyRender = "False"
即可。
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有了 TBBasePage 的 IsVerifyRender 属性后,我们就可以将上述的 ControlToHTML 函式,改写如下。当 GridView 控件置放在 TBBasePage 时,执行 ControlToHTML 函式时,不需另行设定即能正常执行。
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