c# - datatrigger on enum to change image

Question

I've got a button with a fixed background image and would like to show a small overlay image on top of it. Which overlay image to chose depends on a dependency property (LapCounterPingStatus) of the according viewmodel.

This is what I got so far:

<Button>
    <Grid>
        <Image Stretch="None"> <!-- Background Image -->
            <Image.Style>
                <Style TargetType="{x:Type Image}">
                    <Setter Property="Source" Value="/Images/Pingn.png"/>
                </Style>
            </Image.Style>
        </Image>
        <Image Stretch="None" Panel.ZIndex="1"> <!-- Small Overlay Image -->
            <Image.Style>
                <Style TargetType="{x:Type Image}">
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding Path=LapCounterPingStatus}" Value="PingStatus.PING_UNKNOWN">
                            <Setter Property="Source" Value="/Images/RefreshOverlayn.png"/>
                        </DataTrigger>
                        <DataTrigger Binding="{Binding Path=LapCounterPingStatus}" Value="PingStatus.PING_FAILURE">
                            <Setter Property="Source" Value="/Images/ErrorOverlayn.png"/>
                        </DataTrigger>
                        <DataTrigger Binding="{Binding Path=LapCounterPingStatus}" Value="PingStatus.PING_SUCCESS">
                            <Setter Property="Source" Value="/Images/CheckmarkOverlayn.png"/>
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </Image.Style>
        </Image>
    </Grid>
</Button>

Relevant parts of my viewmodel

public class ConfigurationViewModel
{
    public enum PingStatus { PING_UNKNOWN, PING_SUCCESS, PING_FAILURE };

    public PingStatus LapCounterPingStatus
    {
        get { return _lapCounterPingStatus; }
        set
        {
            _lapCounterPingStatus = value;
            RaisePropertyChanged(LapCounterPingStatusPropertyName);
        }
    }
}

Right now, no overlay image at all is displayed. What could be wrong?

---

UPDATE

Trace window of my IDE is showing System.ArgumentException and System.FormatException. Could the problem source be a unknown type of enumeration PingStatus im the XAML?

Answer 1

You need 2 things to get this working:

1 - Add an xmlns reference in the root element of your XAML file, to the namespace where your Enum is defined:

<UserControl ...
xmlns:my="clr-namespace:YourEnumNamespace;assembly=YourAssembly"> 

2 - in the Value property of the DataTrigger, use the {x:Static} form:

 <DataTrigger Binding="{Binding Path=LapCounterPingStatus}" Value="{x:Static my:PingStatus.PING_UNKNOWN}">

Notice that the Enum type must be prefixed with the xmlns prefix you defined above.

Edit:

If your Enum is declared inside a class you need to use the syntax:

{x:Static namespace:ClassName+EnumName.EnumValue}

for example:

{x:Static my:ConfigurationViewModel+PingStatus.PING_UNKNOWN}