KeyedCollection和d：DataContext设计错误 [英] KeyedCollection and d:DataContext Design Error

问题描述

请参见下面针对VS2013的更新。

See the update below for VS2013.

将类用作 d：DesignInstance 时，它公开了一个 KeyedCollection< TKey，TItem> ，XAML设计器抱怨以下警告：

When using a class as a d:DesignInstance that exposes a KeyedCollection<TKey, TItem>, the XAML designer complains with the following warning:

提供的泛型参数数量不等于
泛型类型定义的数量。

The number of generic arguments provided doesn't equal the arity of the generic type definition.

参数名称：实例化

可以使用以下简单程序重现该问题：

The problem can be reproduced with the following simple program:

<Window x:Class="Test.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:local="clr-namespace:Test"
        mc:Ignorable="d"  
        d:DataContext="{d:DesignInstance local:MyClass}" />

namespace Test
{
    public partial class MainWindow : Window
    {
        public MainWindow() { InitializeComponent(); }
    }

    public class MyClass
    {
        public KeyedCollection<string, object> SettingsModule { get; private set; }
    }
}

我无法提供任何公开了 KeyedCollection 的类。

I'm unable to provide design time shape with any class that exposes a KeyedCollection.

有什么想法吗？

更新：自VS2013起，设计人员处理 KeyedCollection 的行为已更改（

Update: As of VS2013 the behavior of the designer in dealing with a KeyedCollection has changed (though still not fully working).

上面的示例不再产生错误。但是，如果 KeyedCollection 使用某些类型（例如接口）作为 TItem ，则会产生以下错误：

The above example no longer generates an error. However, if the KeyedCollection uses certain types (such as an interface) as the TItem the following error is generated:

对象引用未设置为对象的实例。

Object reference not set to an instance of an object.

请考虑以下示例：

namespace Test
{
    public partial class MainWindow : Window
    {
        public MainWindow() { InitializeComponent(); }
    }

    public class MyClass
    {
        public KeyedCollection<string, IInterface> MyCollection { get; private set; }
    }

    public interface IInterface
    {
        string Name { get; set; }
    }
}

推荐答案

我已经可以通过在设计实例类型前面加上 d：Type来解决此问题：

I've been able to resolve this issue by prefixing the design instance type with "d:Type" as such:

d:DataContext="{d:DesignInstance d:Type=local:MyClass}"

这似乎是一个VS2013设计器中的错误。我相信d：Type属性应该是 d：DesignInstance 属性的默认属性。另外，奇怪的是，我只在 KeyedCollection 类中看到过此问题。

This seems to be a bug in the VS2013 designer. I believe the d:Type property should be the default property of the d:DesignInstance attribute. Also, strangely I've only seen this issue with the KeyedCollection class.

此外， d：DesignInstance MSDN示例 $ c>用法有时使用不带前缀的类型。在此示例中，如果省略了 d：Type 或缺少前缀，则会生成设计时错误，如我所述。

Furthermore, the MSDN examples of d:DesignInstance usage sometimes use "Type" with no prefix. In this example if d:Type is omitted or the prefix is missing, the design time error is generated as I mentioned.

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