Cannot Get a ComboBox to Show the Items Properly

Question

I have created a very simple project to illustrate my problem. I fear the resolution is simple but for the life of me I can't see it.

I have but one model:

Public Class SECategory
    Public Property CategoryID As Integer
    Public Property Plural As String
....
End Class

The MainWindow to display the model has only a ComboBox:

<Window>
....
<Window.DataContext>
    <self:ListsVM />
        </Window.DataContext>
    <i:Interaction.Triggers>
        <i:EventTrigger
            EventName="Loaded">
            <i:InvokeCommandAction Command="{Binding LoadMe}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
    <ListBox
        DisplayMemberPath="Plural"
        ItemsSource="{Binding Source=SECategories}"
        Margin="20"
        SelectedItem="{Binding Path=CurrentSECategory}" />
</Window>

The ViewModel is (leaving out the boilerplate):

Public Class ListsVM
    Implements INotifyPropertyChanged

    Private ReadOnly Property clsLoadMe As New RelayCommand(AddressOf PerformLoadMe)
    Private Sub PerformLoadMe()
        clsSECategories = <<A populated ObservableCollection(Of SECategory) 
    End Sub

    Public Property CurrentSECategory As SECategory
    Public Property SECategories As ObservableCollection(Of SECategory)

<<Other boilerplace>>
End Class

When I run this, it populates the ClmboBox the items are blank and I get this error:

System.Windows.Data Error: 40 : BindingExpression path error: 'Plural' property not found on 'object' ''Char' (HashCode=6881385)'. BindingExpression:Path=Plural; DataItem='Char' (HashCode=6881385); target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')

I hope you can spot the mistake.

Answer 1

Your code is listbox, so I tested the listbox binding. You could refer to the following code.

<Window x:Class="MainWindow"
       
        xmlns:self="clr-namespace:DataBindindDeml"
        mc:Ignorable="d"
       xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"  
        Title="MainWindow" Height="450" Width="800">
    <Window.DataContext>
        <self:ListsVM />
    </Window.DataContext>
 
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Loaded">
            <i:InvokeCommandAction Command="{Binding LoadMe}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
    <ListBox  
        ItemsSource="{Binding SECategories}"
        Margin="20" Width="300" Height="300"
        SelectedItem="{Binding Path=CurrentSECategory}" >
       
    </ListBox>
</Window>

Codebehind:

Imports System.Collections.ObjectModel
Imports System.ComponentModel
Imports GalaSoft.MvvmLight.Command

Class MainWindow

End Class
Public Class ListsVM
    Implements INotifyPropertyChanged

    Private ReadOnly Property clsLoadMe As New RelayCommand(AddressOf PerformLoadMe)
    Public ReadOnly Property LoadMe As RelayCommand
        Get
            Return clsLoadMe
        End Get
    End Property

    Private Sub PerformLoadMe()
        clsSECategories.Add(New SECategory() With {
        .CategoryID = 1,
        .Plural = "user1"
    })
        clsSECategories.Add(New SECategory() With {
        .CategoryID = 2,
        .Plural = "user2"
    })
        clsSECategories.Add(New SECategory() With {
        .CategoryID = 3,
        .Plural = "user3"
    })
        clsSECategories.Add(New SECategory() With {
        .CategoryID = 5,
        .Plural = "user4"
    })

    End Sub
    Private clsSECategories As ObservableCollection(Of SECategory) = New ObservableCollection(Of SECategory)()


    Public Property SECategories As ObservableCollection(Of SECategory)
        Get
            Return clsSECategories
        End Get
        Set(ByVal value As ObservableCollection(Of SECategory))


            clsSECategories = value
            NotifyPropertyChanged("SECategories")

        End Set
    End Property

    Public Property CurrentSECategory As SECategory

    Public Event PropertyChanged As PropertyChangedEventHandler _
          Implements INotifyPropertyChanged.PropertyChanged

    Private Sub NotifyPropertyChanged(ByVal propertyName As String)
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
    End Sub

End Class
Public Class SECategory
    Public Property CategoryID As Integer
    Public Property Plural As String
    Public Overrides Function ToString() As String
        Return Plural
    End Function
End Class

The result:

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