XAML - MergedDictionaries throwing XmlParseException "item has already been added". Why?
I have the following, very easy to reproduce problem: I'm creating a xaml application which uses resources from another file. The way to go is to create a MergedDictionaries-tag to merge the local and global resources, like this:
<Window>
<Window.Resources>
<ResourceDictionary>
开发者_开发问答 <ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="path.to.xaml.file"/>
<ResourceDictionary>
<Style TargetType="{x:Type Border}" x:Key="TypeBlock">
</Style>
<Style TargetType="{x:Type Border}" x:Key="SetBlock">
</Style>
</ResourceDictionary>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Window.Resources>
....
</Window>
This little piece of code will crash if you run it:
Item has already been added. Key in dictionary: 'System.Windows.Controls.Border' Key being added: 'System.Windows.Controls.Border'
If we remove the MergedDictionaries-tag, the code will run as expected:
<Window>
<Window.Resources>
<Style TargetType="{x:Type Border}" x:Key="TypeBlock">
</Style>
<Style TargetType="{x:Type Border}" x:Key="SetBlock">
</Style>
</Window.Resources>
</Window>
I don't understand why it throws the exception when we use Merged Resources. Off course, the fix is easy enough for now (move the resources to a lower level). It would be nice to know if this is 'normal' behavior...
If your resources are not located in a separate file, then they shouldn't be part of the merged dictionaries. Move them outside like this:
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="path.to.xaml.file"/>
</ResourceDictionary.MergedDictionaries>
<Style TargetType="{x:Type Border}" x:Key="TypeBlock">
</Style>
<Style TargetType="{x:Type Border}" x:Key="SetBlock">
</Style>
</ResourceDictionary>
</Window.Resources>
That said, the error message is a little misleading and may be a result of a bug in the XAML compiler.
精彩评论