blocks|key|1342854|text|问题是基类被定义为抽象的。这导致设计器失败。这个问题在Laurent+Bugnion博客的评论部分有更详细的描述：http://geekswithblogs.net/lbugnion/archive/2007/03/02/107747.aspx|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1342855|entityMap|0|LINK|mutability|MUTABLE|url|http://geekswithblogs.net/lbugnion/archive/2007/03/02/107747.aspx^0|1L|1T|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

The problem was that the base class was defined as abstract. This caused the designer to fail. This problem is described in more detail in the comments section of Laurent Bugnion's blog: <a href="http://geekswithblogs.net/lbugnion/archive/2007/03/02/107747.aspx" rel="noreferrer">http://geekswithblogs.net/lbugnion/archive/2007/03/02/107747.aspx</a>

blocks|key|1343171|text|我在上面找到了一个非常有用的解决方案：http://www.progware.org/Blog/post/WPF-Designer-Error-Could-not-create-an-instance-of-type.aspx。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1343172|此链接解释了WPF设计器窗口如何运行构造函数以XAML格式显示UI以及补救措施:将以下代码片段添加到构造函数代码的任何可能会产生错误的部分：|1343173|if(!System.ComponentModel.DesignerProperties.GetIsInDesignMode(this))
{
+++//code+producing+exception+++++++++
}|code-block|syntax|javascript|1343174|函数名是不言自明的。:)此链接还提供有关XAML调试问题的解决方案。|1343175|entityMap|0|LINK|mutability|MUTABLE|url|http://www.progware.org/Blog/post/WPF-Designer-Error-Could-not-create-an-instance-of-type.aspx^0|J|2M|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|6|7|Y|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|Z|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|9|@]|C|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

I found a very useful solution to this on :
<a href="http://www.progware.org/Blog/post/WPF-Designer-Error-Could-not-create-an-instance-of-type.aspx">http://www.progware.org/Blog/post/WPF-Designer-Error-Could-not-create-an-instance-of-type.aspx</a>.

This link explains how the WPF designer window runs the Constructor to display the UI in XAML and the remedy:
adding the following snippet to any part of constructor code which might be giving error: 

<pre><code>if(!System.ComponentModel.DesignerProperties.GetIsInDesignMode(this))
{
 //code producing exception 
}
</code></pre>

the function name is self explanatory. :) 
This link also provides solutions on debugging issues with XAML.

blocks|key|1342883|text|另一种可能的原因，正如我们刚刚在这里找到的，所以我为未来的用户添加了这个答案，如果项目托管在不受信任的源上，例如文件服务器。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1342884|在这种情况下，设计器不会加载程序集，因此会给出相同的“无法创建实例...”错误。该解决方案仍将构建和调试正常。|1342885|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Another possible cause, as we just found here, so I'm adding this answer for future users, is if the project is hosted on an untrusted source, such as a file server.

In that case, the designer wouldn't load the assembly and so gave the same "Could not create instance..." error. The solution would still build and debug OK.

blocks|key|1558538|text|另一个原因。我的控件类有一个从资源初始化的静态字段，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1558539|+static+Color+s_ImgColor+=+(Color)TheApp.Resources["PhoneForegroundColor"];|code-block|syntax|javascript|1558540|这将在XAML编辑器中引发空引用异常，因为资源在设计模式下不可用。如果它不是一个颜色资源(比方说，画笔)，这将不是一个问题，但是类型转换为值类型会抛出一个空引用。|1558541|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Another cause. My control class had a static field that was initialized from resources, like this:

<pre><code> static Color s_ImgColor = (Color)TheApp.Resources["PhoneForegroundColor"];
</code></pre>

That would throw a null reference exception in XAML editor, since the resources are not available in design mode. Were it not a color resource (say, a brush), this won't be a problem, but a typecast to value type throws up on a null reference.

blocks|key|1558456|text|还有另一个可能的原因。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1558457|我有一个用户控件，它有生成事件的子控件，例如列表控件上的selection_changed。select_changed事件处理程序对其他子控件进行更改。|1558458|在初始化期间，列表框的selected+item属性发生更改并触发selection_changed事件。处理程序尝试更新其他子控件，但无法更新，因为它们尚未实例化。这会导致空指针异常并导致问题。|1558459|一旦处理了空指针问题，该控件就能够被实例化并出现在父控件中。|1558460|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|L|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|M|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

Yet another possible cause.

I have a user control which has child controls which generate events e.g. selection_changed on list control. The select_changed event handler makes changes to other child controls.

During initialisation the selected item property of the list box gets changed and triggers a selection_changed event. The handler tries to update the other child controls but cannot because they have not yet been instantiated. This leads to a null pointer exception and causes the problem.

Once the null pointer problem was handled the control was able to be instantiated and appeared in the parent control.

blocks|key|1342969|text|我有一个问题，我的MVVM类在构造函数中访问数据库，这就是问题所在，它抛出了一个异常。我只需要检查应用程序是否在设计模式下运行。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1342970|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I have the problem that my MVVM class have acces to the database in the constructor and that was the problem, it throws an exception. I only have to check if application is runing in Design mode.

blocks|key|1558605|text|在WinForms中，如果您使用自定义TypeDescriptionProvider通知设计器具体实现，则可以使用带有抽象控件的设计器：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1558606|我正在使用this+answer中的解决方案来解决另一个问题，即链接this+article的问题。本文推荐使用自定义TypeDescriptionProvider和抽象类的具体实现。设计器将询问自定义提供程序要使用哪些类型，您的代码可以返回具体的类，这样当您完全控制抽象类作为具体类的显示方式时，设计器就会感到满意。|1558607|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/6817281/39396|1|http://wonkitect.wordpress.com/2008/06/20/using-visual-studio-whidbey-to-design-abstract-forms/^0|J|N|0|1N|N|5|B|0|Y|C|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]|$9|10|A|11|1|12]]|E|$]]|$1|H|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]|P|$5|K|L|M|E|$N|Q]]]]

In WinForms, it's possible to use the designer with abstract controls if you use a custom <code>TypeDescriptionProvider</code> to inform the designer of a concrete implementation:

I'm using the solution in <a href="https://stackoverflow.com/a/6817281/39396">this answer</a> to another question, which links <a href="http://wonkitect.wordpress.com/2008/06/20/using-visual-studio-whidbey-to-design-abstract-forms/" rel="nofollow noreferrer">this article</a>. The article recommends using a custom <code>TypeDescriptionProvider</code> and concrete implementation of the abstract class. The designer will ask the custom provider which types to use, and your code can return the concrete class so that the designer is happy while you have complete control over how the abstract class appears as a concrete class.

blocks|key|1558736|text|我得到这个错误的原因很简单，但对我来说很难追踪到。我的转换程序类不是公共的。只需更改类的可访问性就可以解决这个问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1558737|++++public+class+StringToLowerConverter+:+IValueConverter|code-block|syntax|javascript|1558738|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The reason why I was getting this error was simple but tough for me to track down. My converter class was not public. Simply changing the class's accessibility fixed it.

<pre><code> public class StringToLowerConverter : IValueConverter
</code></pre>

blocks|key|1558793|text|我不知道问题是什么，但我是这样解决的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1558794|您不应该在BaseClass的构造函数中执行代码，而应该从父类的构造函数中执行。|1558795|您可以在BaseClass中创建一个方法，并从父类的构造函数执行该方法。|1558796|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

I don't know what the problem is, but I solved it like this:

You should not execute the code in the constructor of your BaseClass but from the constructor of the parent class.

You create a method in the BaseClass that you execute from the constructor of the parent class.

blocks|key|1558896|text|​|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1558897|📷|atomic|offset|length|1558898|1558899|耶！我解决了。在我将Control显示选项设置为Only+Display+Platform+Control后，窗体最终显示在显示器上&错误消失了。请查看该图像以找到它。|1558900|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/9b9424e4f3052496046a545e32a6f2d2.png|imageAlt^0|0|0|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@$E|U|F|V|1|W]]|A|$]]|$1|G|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|Y|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|Q|R|-4]]]]

<a href="https://i.stack.imgur.com/B90O8.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/B90O8.png" alt="enter image description here" /></a>
Yeay! I solved it. The form ended up showing on the Display &amp; error gone after I set the Control Display Options to Only Display Platform Control. Check out the image to locate it.

In my UI XAML I'm essentially inheriting from a class "BaseView" that contains functionality common to several forms, however this is preventing the designer from displaying the form: "Could not create instance of type BaseView". The code will compile and run, but it is frustrating not to be able to see the form in the Designer. Is there a better way? Thanks. 

XAML:

<pre><code>&lt;vw:BaseView 
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 xmlns:vw="clr-namespace:ReviewClient" 
 x:Class="ReviewClient.MainPage"
</code></pre>

...

WPF Designer "Could not create an instance of type"

数据库

服务器

在我的UI中，我基本上继承了一个类"BaseView“，它包含了几个表单通用的功能，但是这阻止了设计器显示表单：”无法创建BaseView类型的实例“。代码将编译并运行，但在设计器中看不到窗体是令人沮丧的。有没有更好的方法？谢谢。XAML：<vw:BaseView xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentatio

问WPF设计器“无法创建类型的实例”
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