MainViewModel.vb

Imports System
Imports System.ComponentModel
Imports System.Threading
Imports DevExpress.Mvvm
Imports DevExpress.Mvvm.DataAnnotations

Namespace SplashScreenManagerExample.ViewModels

    Public Class MainViewModel
        Inherits ViewModelBase

        Public ReadOnly Property SplashScreenManagerService As ISplashScreenManagerService
            Get
                Return GetService(Of ISplashScreenManagerService)()
            End Get
        End Property

        Public ReadOnly Property DispatcherService As IDispatcherService
            Get
                Return GetService(Of IDispatcherService)()
            End Get
        End Property

        Private worker As BackgroundWorker

        Public Function CanStart() As Boolean
            Return worker Is Nothing OrElse Not worker.IsBusy
        End Function

        <Command(CanExecuteMethodName:="CanStart")>
        Public Sub Start()
            If SplashScreenManagerService IsNot Nothing Then
                SplashScreenManagerService.ViewModel = New DXSplashScreenViewModel()
                InitSplashScreenViewModel(SplashScreenManagerService.ViewModel)
                SplashScreenManagerService.Show()
                RunBackgroundWorker()
            End If
        End Sub

        Private Sub RunBackgroundWorker()
            worker = New BackgroundWorker()
            AddHandler worker.DoWork, AddressOf Worker_DoWork
            worker.WorkerSupportsCancellation = True
            worker.RunWorkerAsync()
        End Sub

        Private Sub Worker_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs)
            Dim i As Integer = -1
            While Interlocked.Increment(i) < 100
                If worker.CancellationPending Then
                    e.Cancel = True
                    Exit While
                End If

                UpdateSplashScreenContent(i)
                Thread.Sleep(200)
            End While

            DispatcherService.Invoke(Sub()
                SplashScreenManagerService.Close()
                RemoveHandler worker.DoWork, AddressOf Worker_DoWork
                worker = Nothing
            End Sub)
        End Sub

        Private Sub UpdateSplashScreenContent(ByVal progressValue As Integer)
            Dim state = String.Empty
            state = If(progressValue < 20, "Starting...", If(progressValue < 70, "Loading data..", "Finishing"))
            DispatcherService.Invoke(Sub()
                SplashScreenManagerService.ViewModel.Progress = progressValue
                SplashScreenManagerService.ViewModel.Status = $"({progressValue} %) - {state}"
            End Sub)
        End Sub

        Private Sub InitSplashScreenViewModel(ByVal vm As DXSplashScreenViewModel)
            vm.Title = "SOME BACKGROUND WORK"
            vm.Subtitle = "This can take some time"
            vm.Logo = New Uri("pack://application:,,,/logo.png")
            vm.IsIndeterminate = False
            vm.Tag = New DelegateCommand(AddressOf CancelOperation, AddressOf CanCancelOperation)
        End Sub

        Public Function CanCancelOperation() As Boolean
            Return worker IsNot Nothing AndAlso worker.IsBusy
        End Function

        Public Sub CancelOperation()
            If worker IsNot Nothing AndAlso worker.IsBusy Then worker.CancelAsync()
        End Sub
    End Class
End Namespace