public DataTemplate ButtonTemplate { get; set; }

Public Property ButtonTemplate As DataTemplate

<dxe:ButtonEdit ButtonsSource="{Binding Items}">
    <dxe:ButtonEdit.ButtonTemplate>
        <DataTemplate>
            <ContentControl>
                <dxe:ButtonInfo Command="{Binding Command}"
                                Content="{Binding Content}"
                                IsLeft="{Binding IsLeft}"/>
            </ContentControl>
        </DataTemplate>
    </dxe:ButtonEdit.ButtonTemplate>
</dxe:ButtonEdit>

public class MainViewModel : ViewModelBase {

    private IMessageBoxService MessageBoxService { get { return GetService<IMessageBoxService>(); } }

    public ObservableCollection<ButtonViewModel> Items {
        get { return GetProperty(() => Items); }
        set { SetProperty(() => Items, value); }
    }
    public MainViewModel() {
        Items = new ObservableCollection<ButtonViewModel>() {
            new ButtonViewModel() {
                Content = "A",
                Command = new DelegateCommand(()=> {
                    MessageBoxService.ShowMessage("A");
                }),
                IsLeft = true,
            },
            new ButtonViewModel() {
                Content = "B",
                Command = new DelegateCommand(()=> {
                    MessageBoxService.ShowMessage("B");
                }),
                IsLeft = true,
            },
            new ButtonViewModel() {
                Content = "C",
                Command = new DelegateCommand(()=> {
                    MessageBoxService.ShowMessage("C");
                }),
                IsLeft = true,
            },
            new ButtonViewModel() {
                Content = "X",
                Command = new DelegateCommand(()=> {
                    MessageBoxService.ShowMessage("X");
                }),
            },
            new ButtonViewModel() {
                Content = "Y",
                Command = new DelegateCommand(()=> {
                    MessageBoxService.ShowMessage("Y");
                }),
            },
            new ButtonViewModel() {
                Content = "Z",
                Command = new DelegateCommand(()=> {
                    MessageBoxService.ShowMessage("Z");
                }),
            },
            new ButtonViewModel() {
                Content = "Clear",
                Command = new DelegateCommand(()=> {
                    this.Items.Clear();
                    Items = new ObservableCollection<ButtonViewModel>(Items);
                }),
            },
            new ButtonViewModel() {
                Content = "Add",
                Command = new DelegateCommand(()=> {
                    Items.Add(new ButtonViewModel() {
                        Content = "New",
                        IsLeft = this.Items.Count % 2 == 0
                    });
                    Items = new ObservableCollection<ButtonViewModel>(Items);
                }),
            },
        };
    }
}

Public Class MainViewModel
    Inherits ViewModelBase

    Private ReadOnly Property MessageBoxService() As IMessageBoxService
        Get
            Return GetService(Of IMessageBoxService)()
        End Get
    End Property

    Public Property Items() As ObservableCollection(Of ButtonViewModel)
        Get
            Return GetProperty(Function() Items)
        End Get
        Set(ByVal value As ObservableCollection(Of ButtonViewModel))
            SetProperty(Function() Items, value)
        End Set
    End Property
    Public Sub New()
        Items = New ObservableCollection(Of ButtonViewModel)() From {
            New ButtonViewModel() With {
                .Content = "A",
                .Command = New DelegateCommand(Function() MessageBoxService.ShowMessage("A")),
                .IsLeft = True
            },
            New ButtonViewModel() With {
                .Content = "B",
                .Command = New DelegateCommand(Function() MessageBoxService.ShowMessage("B")),
                .IsLeft = True},
            New ButtonViewModel() With {
                .Content = "C",
                .Command = New DelegateCommand(Function() MessageBoxService.ShowMessage("C")),
                .IsLeft = True},
            New ButtonViewModel() With {
                .Content = "X",
                .Command = New DelegateCommand(Function() MessageBoxService.ShowMessage("X"))
            },
            New ButtonViewModel() With {
                .Content = "Y",
                .Command = New DelegateCommand(Function() MessageBoxService.ShowMessage("Y"))},
            New ButtonViewModel() With {
                .Content = "Z",
                .Command = New DelegateCommand(Function() MessageBoxService.ShowMessage("Z"))},
            New ButtonViewModel() With {
                .Content = "Clear",
                .Command = New DelegateCommand(
                    Sub()
                        Items.Clear()
                        Items = New ObservableCollection(Of ButtonViewModel)(Items)
                    End Sub)
            },
            New ButtonViewModel() With {
                .Content = "Add",
                .Command = New DelegateCommand(
                    Sub()
                        Items.Add(New ButtonViewModel() With {
                            .Content = "New",
                            .IsLeft = Items.Count Mod 2 = 0
                        })
                        Items = New ObservableCollection(Of ButtonViewModel)(Items)
                    End Sub)
            }
        }
    End Sub
End Class

public class ButtonViewModel : ViewModelBase {
    public string Content {
        get { return GetProperty(() => Content); }
        set { SetProperty(() => Content, value); }
    }
    public ICommand Command {
        get { return GetProperty(() => Command); }
        set { SetProperty(() => Command, value); }
    }
    public bool IsLeft {
        get { return GetProperty(() => IsLeft); }
        set { SetProperty(() => IsLeft, value); }
    }
}

Public Class ButtonViewModel
    Inherits ViewModelBase

    Public Property Content() As String
        Get
            Return GetProperty(Function() Content)
        End Get
        Set(ByVal value As String)
            SetProperty(Function() Content, value)
        End Set
    End Property
    Public Property Command() As ICommand
        Get
            Return GetProperty(Function() Command)
        End Get
        Set(ByVal value As ICommand)
            SetProperty(Function() Command, value)
        End Set
    End Property
    Public Property IsLeft() As Boolean
        Get
            Return GetProperty(Function() IsLeft)
        End Get
        Set(ByVal value As Boolean)
            SetProperty(Function() IsLeft, value)
        End Set
    End Property
End Class