HOWTO避免"未设置到对象&QUOT的实例对象的引用;而在设计时XAML代码例外？ [英] Howto avoid a "object reference not set to an instance of an object" exception in XAML code while design time?

问题描述

我有一个WPF用户控件这是我自己设计的一个问题。
的问题是，我收到了对象引用不设置到对象的实例例外XAML代码而设计的时候，当我实现我在程序的用户控件

如何解决或抑制exeption？

编辑1

设计师告诉我以下信息：

在
Microsoft.Expression.Platform.InstanceBuilders.InstanceBuilderOperations .InstantiateType在
Microsoft.Expression.Platform.InstanceBuilders.ClrObjectInstanceBuilder.InstantiateTargetType（IInstanceBuilderContext
的背景下，ViewNode viewNode）在
Microsoft.Expression.Platform（输入
型，布尔supportInternal）在
Microsoft.Expression.WpfPlatform.InstanceBuilders.FrameworkElementInstanceBuilder.Instantiate（IInstanceBuilderContext
的背景下，viewNode viewNode）.InstanceBuilders.ClrObjectInstanceBuilder.Instantiate（IInstanceBuilderContext
的背景下，viewNode viewNode）在
微软在
Microsoft.Expression.Platform.InstanceBuilders.ViewNodeManager.CreateInstance（IInstanceBuilder
建设者，viewNode viewNode）<.Expression.WpfPlatform.InstanceBuilders.UserControlInstanceBuilder.Instantiate（IInstanceBuilderContext
的背景下，viewNode viewNode）/ p>

我想他们是不是真的有帮助...

解决方案

无论是在你的构造发生在设计时被抛出异常。我有同样的问题 - 我只是把周围有问题的代码尝试catch - 在我的情况下我使用IoC容器我打电话ServiceLocator.Current。但是，在设计时没有容器。所以我包裹在一个尝试捕捉取消错误和它的工作。不是最好的解决办法...但它的解决方案。

I have a problem with a wpf usercontrol which is of my own devising. The problem is that i get a object reference not set to an instance of an object exception in XAML code while design time, when I implement the usercontrol in my program.

How can i fix or suppress the exeption?

EDIT 1

The designer show me following information:

at Microsoft.Expression.Platform.InstanceBuilders.InstanceBuilderOperations.InstantiateType(Type type, Boolean supportInternal) at Microsoft.Expression.Platform.InstanceBuilders.ClrObjectInstanceBuilder.InstantiateTargetType(IInstanceBuilderContext context, ViewNode viewNode) at Microsoft.Expression.Platform.InstanceBuilders.ClrObjectInstanceBuilder.Instantiate(IInstanceBuilderContext context, ViewNode viewNode) at Microsoft.Expression.WpfPlatform.InstanceBuilders.FrameworkElementInstanceBuilder.Instantiate(IInstanceBuilderContext context, ViewNode viewNode) at Microsoft.Expression.WpfPlatform.InstanceBuilders.UserControlInstanceBuilder.Instantiate(IInstanceBuilderContext context, ViewNode viewNode) at Microsoft.Expression.Platform.InstanceBuilders.ViewNodeManager.CreateInstance(IInstanceBuilder builder, ViewNode viewNode)

I think they are not really helpful...

解决方案

Whatever is happening in your constructor is throwing an exception during design time. I had same problem - I just put a try catch around the problematic code - in my case I was calling ServiceLocator.Current as I am using an IoC container. But there is no container during design time. So I wrapped in a try catch to suppress the error and it worked. Not the best solution... but its a solution.

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