How to set properties of a d:DesignInstance in XAML?

wpf, xaml

Solution

As @jberger you should probably use `d:DesignData` instead of inlining a `d:DataContext`.

However you can set the d:DataContext inline in the xaml file as well, the secret is to use the correct class (`DesignProperties`) to qualify the `d:DataContext` property:

<d:DesignProperties.DataContext>
   <plugin:SamplePendingChangesViewModel ActiveTagIndex="2"/>
</d:DesignProperties.DataContext>

How do you know what class to qualify with? Mouse over a property that is set in attribute syntax and a tooltip will appear with the fully qualified property name.

Note also that im not using the `d:DesignInstance` markup exstension as its job specifically is to create a instance of a type that you provide the name for (or generate a proxy of that type if it cant be instanciated at design-time). Thats not what we want, we want to define the instance in inline xaml in this case.

Indeed, `d:DesignData` (also a markup extension) works much the same way, except that it looks for a xaml file and deserializes that to the actual instance to use instead of just using the default constructor.

Just for completeness i should also mention that you can use DesignData and DesignInstance with element syntax as well by using their full class names (xxxExtension):

<d:DesignProperties.DataContext>
  <d:DesignDataExtension Source="SampleData.xaml"></d:DesignDataExtension>
</d:DesignProperties.DataContext>

This is true for most markup exstensions but its not required to follow this naming convension (The Binding class is a notable exception) More info can be found here:

Markup Extensions and WPF XAML

Problem

I'm using the new d:DesignInstance feature of the 4.0 series WPF tools. Works great! Only issue I'm having is: how can I set properties on the instance? Given something like this: ``` <Grid d:DataContext="{d:DesignInstance plugin:SamplePendingChangesViewModel, IsDesignTimeCreatable=True}"/> ``` How can I set properties on the viewmodel, aside from setting them in its default ctor or routing it through some other object initializer? I gave this a try but VS gives errors on compile "d:DataContext was not found": ``` <Grid> <d:DataContext> <d:DesignInstance IsDesignTimeCreatable="True"> <plugin:SamplePendingChangesViewModel ActiveTagIndex="2"/> </d:DesignInstance> </d:DataContext> ``` For the moment I'm going back to using a resource and 'd:DataContext={StaticResource SampleData}', where I can set the properties in the resource. Is there a way to do it via a d:DesignInstance?

Original source