At present, the style for the internal card on the dialog host is not exposed, so there is no simple way to expose that.

@Keboo The dailog host content is so blurry with default card style. Can you add a new style named "MaterialDesignOutlinedDialogHost"?

...
<wpf:Card.Style>
   <Style TargetType="wpf:Card" BasedOn="{StaticResource MaterialDesignOutlinedCard}">
     <Setter Property="Background" Value="{Binding Tag, RelativeSource={RelativeSource Self}}" />
     <Style.Triggers>
       <Trigger Property="Tag" Value="{x:Null}">
         <Setter Property="Background" Value="{DynamicResource MaterialDesignPaper}" />
       </Trigger>
     </Style.Triggers>
   </Style>
 </wpf:Card.Style>\
...

How to remove the shadow of the Dialog box?

@mkc-xuliangjie you can set the Attached Property ElevationAssist.Elevation to Dp0 in the DialogHost like the following:

<materialDesign:DialogHost materialDesign:ElevationAssist.Elevation="Dp0">
  ...
</materialDesign:DialogHost>

This removes all elevation ("shadows") of the dialog.
Here is an example comparing Dp0 with Dp24: