How can I use enum types in XAML?

There's no need to make life so complicated. Enum is easily convertible to string, so you can use that string value in tirgger.

<Image.Style>
    <Style TargetType="{x:Type Image}">
        <Style.Triggers>
            <DataTrigger Binding="{Binding Type}" Value="Type_DB">
                <Setter Property="Source" Value="/Images/DB.PNG"/>
            </DataTrigger>
            <DataTrigger Binding="{Binding Type}" Value="Type_SERVER">
                <Setter Property="Source" Value="/Images/SERVER.PNG"/>
            </DataTrigger>
        </Style.Triggers>
    </Style>
</Image.Style>

---

But if you store an int value in your enum... because you can assign:

NodeType val = (NodeType)619;

then... Yes... you have to use a converter.

You just need to make sure that your namespace is accounted-for in your XAML header then you can reference both custom DPs and enum values directly in your markup.

For example I use this code to do just that:

<DataTemplate.Triggers>
  <MultiDataTrigger>
    <MultiDataTrigger.Conditions>
      <Condition Binding="{Binding IsMouseOver, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBoxItem}}}" Value="True" />
      <Condition Binding="{Binding Type}" Value="{x:Static loc:AppProfileItemType.Custom}" />
    </MultiDataTrigger.Conditions>
    <MultiDataTrigger.Setters>
      <Setter TargetName="PART_Delete" Property="Visibility" Value="{x:Static Visibility.Visible}" />
    </MultiDataTrigger.Setters>
  </MultiDataTrigger>
</DataTemplate.Triggers>

Note that you can't access DataTriggers in a Style, you need to instead make a DataTemplate or ControlTemplate for that (however, .NET 4 adds the ability to set triggers in styles). You can override the ControlTemplate from a Style like so:

<Style x:Key="MyCustomButtonStyle" TargetType="Button">
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="Button">
        <ContentPresenter />
        <ControlTemplate.Triggers>
          <!-- Put your DataTriggers here -->
        </ControlTemplate.Triggers>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>

For DataTemplates you want to have bindings to an object, you can simply use a ContentPresenter and set its content to the object you want to display along with a DataTemplate definition to use for display of the object. There's always a way to use DataTriggers it's just not always direct or as simple as using a Style.

I had a similar question here, and my end result was to create a generic IValueConverter that passed the enum value I wanted to match in as the ConverterParameter, and it returns true or false depending on if the bound value matches the (int) value of the Enum.

The end result looks like this:

XAML Code:

<DataTrigger Value="True"
             Binding="{Binding SomeIntValue, 
                 Converter={StaticResource IsIntEqualEnumConverter},
                 ConverterParameter={x:Static local:NodeType.Type_DB}}">

Converter

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    if (parameter == null || value == null) return false;

    if (parameter.GetType().IsEnum && value is int)
    {
        return (int)parameter == (int)value;
    } 
    return false;
}