Question

All –

Need some insight into this issue. I have created a sample project to isolate the issue on one of my projects. I am trying to set the background of my Border based on a certain value in the model (Int/String/Enum).

The issue I am having is:

1) I believe the source in the DataTrigger Binding is being set – but I am still getting this error:
personId property not found on ‘object’ ”String’. BindingExpression:Path=personId; DataItem=’String’ (HashCode=1896530089); target element is ‘Border’ (Name=”); target property is ‘NoTarget’ (type ‘Object’)

2) I was doing this on int (or string) just to make the concept work. But realistically I need to make this of the Enum value. any suggestions on this will also help.

Here are the code snippets:

Person.cs

public class Person
{
    public int personId { get; set; }
    public string personName { get; set; }
    public Gender personType { get; set; }

    public enum Gender
    {
        Male,
        Female
    }
}

PersonViewModel.cs

public class PersonViewModel
{
    private ObservableCollection<Person> _people;

    public ObservableCollection<Person> people
    {
        get
        {
            return _people;
        }
    }

    public PersonViewModel()
    {
        _people = new ObservableCollection<Person>()
        {
            new Person()
            {
                personId = 1,
                personName = "John",
                personType = Person.Gender.Male
            },

            new Person()
            {
                personId = 1,
                personName = "Mary",
                personType = Person.Gender.Female
            },
        };
    }
}

PersonView.xaml.cs

public PersonView()
    {
        InitializeComponent();
         var personvm = new PersonViewModel();
        DataContext = personvm;
    }

PersonView.xaml

 <Window.Resources>
    <Style x:Key="BorderGradient" TargetType="{x:Type Border}">
        <Style.Triggers>
            <DataTrigger Binding="{Binding Source=people, Path=personId}" Value="1">
                <Setter Property="Background">
                    <Setter.Value>
                        <LinearGradientBrush StartPoint="0.5,0" EndPoint="0.511,0.957">
                            <GradientStop Color="LightGray" Offset="0.55" />
                            <GradientStop Color="Black" Offset="1.3" />
                        </LinearGradientBrush>
                    </Setter.Value>
                </Setter>
            </DataTrigger>
            <DataTrigger Binding="{Binding Source=people, Path=personId}" Value="2">
                <Setter Property="Background">
                    <Setter.Value>
                        <LinearGradientBrush StartPoint="0.5,0" EndPoint="0.511,0.957">
                            <GradientStop Color="LightGray" Offset="0.55" />
                            <GradientStop Color="Yellow" Offset="1.3" />
                        </LinearGradientBrush>
                    </Setter.Value>
                </Setter>
            </DataTrigger>
        </Style.Triggers>
    </Style>
</Window.Resources>

<Border CornerRadius="15,15,15,15" Style="{StaticResource BorderGradient}" >
    <Grid Width="Auto" MinWidth="750" Height="Auto" MinHeight="600">

<!-- Logic in VM where visibility would be set through VM -->

        <StackPanel Grid.Row="0" HorizontalAlignment="Center" VerticalAlignment="Top" Visibility="To be set" >
            <loc:MaleView/>
        </StackPanel>

        <StackPanel Grid.Row="1" HorizontalAlignment="Center"  Visibility=" to be set">
            <loc:FemaleView />
        </StackPanel>
    </Grid>
</Border>

Answer 1

people is an observable collection, which is what you’re binding to in your datatrigger. The ObservableCollection doesn’t have a property named “personId”.

It would probably be better to have a DataTemplate for your PersonViewModel

<DataTemplate DataType={x:Type vm:PersonViewModel}">

   <Grid Background="Red">
         .. Template For PersonViewModel Here ..
   </Grid>

   <DataTemplate.Triggers>
      <DataTrigger Binding="{Binding Path=personId}" Value="1">
         .... do stuff
      </DataTrigger>
   </DataTemplate.Triggers>
</DataTemplate>