如何使用 Windbg 判断 .Net 控件是否可见

发布于 2024-08-08 09:15:13 字数 154 浏览 2 评论 0原文

我收到了一个故障转储，我们正在其中讨论控件是否对最终用户可见。使用 !do 进行查看时，我看不到任何包含与 Visible 属性匹配的 true/false 值的显式字段，这并不奇怪，因为我们可能处于 win32 领域。有谁知道如何推断从转储文件中返回的可见内容？

谢谢奥斯卡

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尐籹人 2024-08-15 09:15:13

我最初的想法是这只是一个寻找正确领域的问题，但实际上需要更多的挖掘。如果您查看 Reflector 中的 Control，您会发现 Visible 属性调用 GetVisibleCore，它根据值 2（恰好是常量 STATE_VISIBLE）检查内部状态字段。

因此，为了查明控件是否可见，我们需要找到状态字段并进行一些位操作。

如果您有实例的地址，则可以执行以下操作：

.shell -ci "!do <ADDRESS>" grep state   (use findstr, if you don't have grep)

输出类似于此

0:000> .shell -ci "!do 015892a4" grep state
03aeedcc  400112c       4c         System.Int32  1 instance 17432589 state  <=== HERE!
03aeedcc  400112d       50         System.Int32  1 instance     2060 state2
049ac32c  40011ef       d0 ...lized.BitVector32  1 instance 01589374 state
03aeedcc  40011f0      ad4         System.Int32  1   static        1 stateScalingNeededOnLayout
03aeedcc  40011f1      ad8         System.Int32  1   static        2 stateValidating
03aeedcc  40011f2      adc         System.Int32  1   static        4     stateProcessingMnemonic
03aeedcc  40011f3      ae0         System.Int32  1   static        8 stateScalingChild
03aeedcc  40011f4      ae4         System.Int32  1   static       16 stateParentChanged

通知，有两个状态字段。我还没有研究为什么会出现这种情况，但你想要的是 System.Int32。在我的示例中，它的值为 17432589。GetState

中的代码如下所示

return ((this.state & flag) != 0);

，因此您只需执行 (17432589 & 2) != 0 即可获得可见状态的具体实例。

事实上，你可能还需要更进一步。如果上面返回 false，则需要查找父级并重复该技巧。对于我使用不必要的表单的简单示例。

My initial thought was that this was just a question of looking up the right field, but actually it took a bit more digging. If you look at Control in Reflector, you'll see that the Visible property calls GetVisibleCore, which checks an internal state field against the value 2 (which happens to be the constant STATE_VISIBLE).

So in order to find out if a control is visible, we need to locate the state field and do some bit manipulation.

If you have the address of the instance, you can do the following:

.shell -ci "!do <ADDRESS>" grep state   (use findstr, if you don't have grep)

The output is something similar to this

0:000> .shell -ci "!do 015892a4" grep state
03aeedcc  400112c       4c         System.Int32  1 instance 17432589 state  <=== HERE!
03aeedcc  400112d       50         System.Int32  1 instance     2060 state2
049ac32c  40011ef       d0 ...lized.BitVector32  1 instance 01589374 state
03aeedcc  40011f0      ad4         System.Int32  1   static        1 stateScalingNeededOnLayout
03aeedcc  40011f1      ad8         System.Int32  1   static        2 stateValidating
03aeedcc  40011f2      adc         System.Int32  1   static        4     stateProcessingMnemonic
03aeedcc  40011f3      ae0         System.Int32  1   static        8 stateScalingChild
03aeedcc  40011f4      ae4         System.Int32  1   static       16 stateParentChanged

Notice, that there are two state fields. I haven't looked into why this is the case, but the one you want is the System.Int32. In my example it has a value of 17432589.

The code in GetState is as follows

return ((this.state & flag) != 0);

so all you have to do from here is (17432589 & 2) != 0 and you'll have the Visible state of the specific instance.

Actually, you may have to go a step further. If the above returns false, you need to look up the parent and repeat the trick. For my simple example using a Form that was not necessary.

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