" Jeremy Chapman" < me@here.com>在消息中写道

新闻：％2 **************** @ TK2MSFTNGP14.phx.gbl ...

我想要从类的外部访问页面对象的视图状态（在辅助类中），所以我创建了一个继承自Page的类，并公开了一个返回viewstate对象的
属性。我的帮助类我将
页面转换为我的页面类并访问公开的属性，但是强制转换导致指定的强制转换无效异常。我曾经在delphi
和c ++中一直这样做以访问受保护的东西，是否可以在.NET中？

在.NET中可以进行强制转换。发布实际的源代码，它会更容易

来帮助你。


- Oliver

我认为你认为你曾经在Delphi中这么做过，但它根本不是

。为什么？因为你只能将一个类型转换为它所属的类型，它是一个类型，它是它的类型，还是它继承的类型。由于您的自定义类

继承了System.Web.UI.Page，您可以将IT转换为System.Web.UI.Page类，

但是您无法投射System.Web.UI.Page类作为您的自定义类。


然而，请加油助威。事实上，你的解决方案是不必要的复杂。

请记住，你的页面不是System.Web.UI.Page类，而是

" YourClassName" class，继承System.Web.UI.Page。 IT可以使用自己的ViewState访问

，并可以通过您选择的任何方法公开它。


-

HTH，


Kevin Spencer

Microsoft MVP

..Net开发人员

期待未被接受。


" Jeremy Chapman" < me@here.com>在消息中写道

新闻：％2 **************** @ TK2MSFTNGP14.phx.gbl ...

我想要从类的外部访问页面对象的视图状态（在辅助类中），所以我创建了一个继承自Page的类，并公开了一个返回viewstate对象的
属性。我的帮助类我将
页面转换为我的页面类并访问公开的属性，但是强制转换导致指定的强制转换无效异常。我曾经在delphi
和c ++中一直这样做以访问受保护的东西，是否可以在.NET？

这里有一些样本来源。


使用系统;


名称空间Mynamespace

{

/ //< summary>

///页面的帮助函数

///< / summary>

公共类HelperClass

{

public HelperClass

{

//

// TODO：Add构造函数逻辑这里

//

}

私有类CustomPage：System.Web.UI.Page

{

public CustomPage（）

{

}


public System.Web.UI.StateBag PublishViewState

{

get

{

返回ViewState;

}

}

}


public static void HelperTest（System.Web.UI.Page pPage）

{

CustomPage pPageCustom =（CustomPage）pPage;

pPageCustom.PublishViewState [" test"] = DateTime.Now;


}

}

}


" Oliver Wong" &LT;流*** @ castortech.com&GT;在消息中写道

新闻：Q18Le.195006

I want to access the viewstate of a page object from outside of the class
(in a helper class), so I made a class inherited from Page, and exposed a
property that returns the viewstate object. I my helper class I cast the
page to my page class and access the exposed property, but the cast causes
an ''Specified cast is not valid'' exception. I used to do this in delphi and
c++ all the time to access protected stuff, is it possible in .NET?

"Jeremy Chapman" <me@here.com> wrote in message
news:%2****************@TK2MSFTNGP14.phx.gbl...

I want to access the viewstate of a page object from outside of the class
(in a helper class), so I made a class inherited from Page, and exposed a
property that returns the viewstate object. I my helper class I cast the
page to my page class and access the exposed property, but the cast causes
an ''Specified cast is not valid'' exception. I used to do this in delphi
and c++ all the time to access protected stuff, is it possible in .NET?

Casting is possible in .NET. Post actual source code and it''ll be easier
to help you.

- Oliver

I think you THINK you used to so this in Delphi, but it is simply not
possible. Why? Because you can only cast a type as a type that it IS, that
is, the type that it is, or a type that it inherits. Since your custom class
inherits System.Web.UI.Page, you can cast IT as a System.Web.UI.Page class,
but you can not cast a System.Web.UI.Page class as your custom class.

However, be of good cheer. In fact, your solution is needlessly complex.
Remember that your Page is not a System.Web.UI.Page class, but a
"YourClassName" class, which inherits System.Web.UI.Page. IT has access to
its own ViewState, and can expose it via any method you choose.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
Expect the unaccepted.

"Jeremy Chapman" <me@here.com> wrote in message
news:%2****************@TK2MSFTNGP14.phx.gbl...

I want to access the viewstate of a page object from outside of the class
(in a helper class), so I made a class inherited from Page, and exposed a
property that returns the viewstate object. I my helper class I cast the
page to my page class and access the exposed property, but the cast causes
an ''Specified cast is not valid'' exception. I used to do this in delphi
and c++ all the time to access protected stuff, is it possible in .NET?

Here is some sample source.

using System;

namespace Mynamespace
{
/// <summary>
/// Helper functions for a page
/// </summary>
public class HelperClass
{
public HelperClass
{
//
// TODO: Add constructor logic here
//
}
private class CustomPage : System.Web.UI.Page
{
public CustomPage()
{
}

public System.Web.UI.StateBag PublishViewState
{
get
{
return ViewState;
}
}
}

public static void HelperTest(System.Web.UI.Page pPage)
{
CustomPage pPageCustom = (CustomPage)pPage;
pPageCustom.PublishViewState["test"] = DateTime.Now;

}
}
}

"Oliver Wong" <ow***@castortech.com> wrote in message
news:Q18Le.195006