xmlns:sys="clr-namespace:System;assembly=System.Runtime"
xmlns:xs="http://schemas.xceed.com/wpf/xaml/toolkit"
<xs:PropertyGrid x:Name="PropertyGrid">
<!--DateTime?-->
<xs:PropertyGrid.EditorDefinitions>
<xs:EditorTemplateDefinition>
<!--Селектор по типу-->
<xs:EditorTemplateDefinition.TargetProperties>
<xs:TargetPropertyType Type="{x:Type sys:Nullable`1[System.DateTime]}" />
</xs:EditorTemplateDefinition.TargetProperties>
<!--Шаблон редактора-->
<xs:EditorTemplateDefinition.EditingTemplate>
<DataTemplate>
<TextBox Text="{Binding Value, Mode=OneWay}" IsEnabled="False">
<TextBox.Resources>
<Style TargetType="{x:Type Border}">
<Setter Property="Visibility" Value="Hidden"/>
</Style>
</TextBox.Resources>
</TextBox>
</DataTemplate>
</xs:EditorTemplateDefinition.EditingTemplate>
</xs:EditorTemplateDefinition>
</xs:PropertyGrid.EditorDefinitions>
</xs:PropertyGrid>