CODEWITHSUNDEEP
vb.netasynchronous
cjw
cjw

Reputation: 354

Using Async/Await correctly in VB

I am having trouble getting a datatable from a WCF service using Async/Await and loading it into a datagridview. This is my first time doing this, I feel like I am missing something basic. This is the code I have so far: 

Private p_oDataService As New SQLService.DataServiceClient

Async Function GetReportDataTable() As Task(Of DataTable)
  Try
    p_oDataService = New SQLService.DataServiceClient
    Dim tDatatable As Task(Of DataTable) = p_oDataService.GetValidationReportsAsync()
    Dim dt As DataTable = Await tDatatable
    Return dt
  Catch ex As Exception
    Throw ex
  End Try
End Function 

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
  Try
    Dim tDT As Task(Of DataTable) = GetReportDataTable()
    Dim dt As DataTable = GetReportDataTable.Result
    DataGridView1.AutoGenerateColumns = True
    DataGridView1.DataSource = dt
  Catch ex As Exception
    Throw ex
  End Try
End Sub

Any help is appreciated!

Upvotes: 2

Views: 13379

Answers (1)

Nkosi
Nkosi

Reputation: 246998

You are mixing blocking and async calls. When you call GetReportDataTable.Result it will deadlock.

Event handlers allow you to await async tasks as well so update the event handler...

Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Try
      Dim dt As DataTable = Await GetReportDataTable()
      DataGridView1.AutoGenerateColumns = True
      DataGridView1.DataSource = dt
    Catch ex As Exception
      Throw ex
    End Try
End Sub

Upvotes: 6

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