Wpf 带MVVM的异步等待进度条

如何使用MVVM实现progressbar或进度状态。下面是我的ViewModel的基本外观。 我基本上是通过在继承的CrudVMBase类中实现Relaycommand来启动getdata函数。当它完成任务时，它将引发ProductModels的属性changed，并在我的xaml中绑定到datagrid，如下所示。这有时需要一个小时。我想为xaml实现一些状态/进度信息。不确定我是否可以使用

Messenger.[Default].SendOf UserMessagemsg

MvvmLight的功能。我使用它已经返回了异常，如下面的try-catch部分所示

Namespace ViewModels


    Public Class CheckProductsViewModel
        Inherits CrudVMBase


        Private m_ProductModels As ObservableCollection(Of ProductVM)
        Public Property ProductModels() As ObservableCollection(Of ProductVM)
            Get
                Return m_ProductModels
            End Get
            Set(value As ObservableCollection(Of ProductVM))
                m_ProductModels = value
            End Set
        End Property

        Public Sub New()
            MyBase.New()
        End Sub

        Private _totalTime As String
        Public Property totalTime() As String
            Get
                Return _totalTime
            End Get
            Set(ByVal value As String)
                _totalTime = value
            End Set
        End Property

        Protected Overrides Async Sub GetData()
            Dim watch As Stopwatch = Stopwatch.StartNew()
            ThrobberVisible = Visibility.Visible
            Try

               Dim myProducts = Await (myContext.Products.Where(Function(w) w.Name <> "").ToListAsync())

                Dim myProductComponent As New ProductComponent
               Dim _ProductModels As ObservableCollection(Of ProductVM)

                Dim counter = 0

                Dim tasks = myProducts.Select(Function(x) myProductComponent.testUrl_async(x))
                Dim results = Await Task.WhenAll(tasks)

              Dim r = (From item In results Where item IsNot Nothing Select New ProductVM With { _
                   .IsNew = False, _
                   .TheProductModel = item _
               }).ToList()

                _ProductModels = New ObservableCollection(Of ProductVM)(r)
                ProductModels = _ProductModels
                watch.Stop()
                totalTime = "total time:" & Math.Round(watch.Elapsed.TotalSeconds).ToString

                RaisePropertyChanged("totalTime")
                RaisePropertyChanged("ProductModels")
            Catch ex As Exception
              Dim msg As New UserMessage()
            msg.isException = True
            msg.Message = ex.ToString
            Messenger.[Default].Send(Of UserMessage)(msg)
            End Try

            ThrobberVisible = Visibility.Collapsed
        End Sub

    End Class


End Namespace

XAML：

---

您不能只向CheckProductsViewModel添加一个进度属性吗？ 使其实现RaisePropertyChanged事件，并在xaml中将该值绑定到ProgressBar的value属性

除非我不清楚这个问题，否则绝对没有必要在这里使用MVVMLight的Messenger

 <Grid>
            <cst:CustomDataGrid x:Name="grdProduct"                                                             
                                  ItemsSource="{Binding ProductModels, IsAsync=True}"                
                 Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"    
                 Style="{StaticResource myDataGrid2}"
                  >
    ....              
 </Grid>