Why does this function fail

[vijaysridhara]

Hi,
Can some one help, why does this function fail? The call jumps to directly "Finally" block without waiting for response. I tried chat.SendAsync also, the same result.
` Private Async Sub SendMessage(msg As String)

 Dim iterator As IAsyncEnumerator(Of String) 'Or appropriate type
 txtHistory.AppendText("You: " & msg)
 txtHistory.AppendText(vbCrLf)

 txtHistory.AppendText("Agent: ")
 txtHistory.SelectionStart = txtHistory.TextLength
 txtHistory.ScrollToCaret()
 Try
     iterator = chat.SendAsAsync(New Models.Chat.ChatRole("user"), msg)

     Do While Await iterator.MoveNextAsync()
         Dim item = iterator.Current
         txtHistory.AppendText(item)
     Loop
 Catch ex As Exception
     txtHistory.AppendText(ex.Message)
 Finally
     txtHistory.AppendText(vbCrLf)
     txtHistory.SelectionStart = txtHistory.TextLength
     txtHistory.ScrollToCaret()
     butSend.Enabled = True
 End Try

End Sub`

[awaescher]

First I would recommend not using "Async Sub" which is the VB equivalent of async void antipattern. Such methods cannot be awaited and might cause errors that will not be catched.

Also, I think the code looks strange but I guess you are using iterator.MoveNextAsync() because that's the VB way to handle IAsyncEnumerable<>. If so, this code might be okay, I don't really know. But you are accessing the UI txtHistory.AppendText(item) directly mixed-in with the async calls. It's pretty likely that you might run into a threading issue.

Anyhow, I guess this is too complex to pin this down remotely.

[vijaysridhara]

I feared threading issues, but there were none, nevertheless, I changed code, to make it into a Async Function. Yes IAsyncEnumerable is the code line iterator as IAsyncEnumerator(of String) . I removed the textbox and just put Debug.Print(item). But no luck.

   Dim url As Uri = New Uri("http://localhost:11434")
   Private WithEvents ollama As OllamaApiClient = New OllamaApiClient(url)
   Dim chatter As Chat
   Private Sub cboModels_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cboModels.SelectedIndexChanged
       If cboModels.SelectedIndex = -1 Then Exit Sub
       SetModel()
   End Sub

   Private Function SetModel() As Boolean
       ollama.SelectedModel = cboModels.Text
       ollama.Config.Model = ollama.SelectedModel
       chatter = Nothing
       chatter = New Chat(ollama)
       chatter.Model = cboModels.Text
       Return True
   End Function

Private Async Function SendMessage(msg As String) As Task(Of Boolean)
     Dim iterator As IAsyncEnumerator(Of String) 'Or appropriate type
     Try
         iterator = chatter.SendAsAsync(New Models.Chat.ChatRole("user"), msg)
         Do While Await iterator.MoveNextAsync()
             Dim item = iterator.Current
             Debug.Print(item)
         Loop
     Catch ex As Exception
            Debug.Print(ex.Message)
     End Try
     Return True
 End Function

[vijaysridhara]

On a button click, the send message enters with message, but quickly comes out.

 Private Sub butSend_Click(sender As Object, e As EventArgs) Handles butSend.Click
   Dim t As Task(Of Boolean)
   t = SendMessage(txtRequest.Text.Trim())
End Sub

[awaescher]

That task is never started.

[vijaysridhara]

What does it mean? It never went inside SendMessage?

[awaescher]

If there's not awaiter for a Task, it might be garbage collected before it's executed.

As a workaround you could use .SafeFireAndForget() from here but keep in mind that it is still a workaround.

Please make sure you fully understand this and this.

[vijaysridhara]

Sure, i will read through, btw, I use .NET 8.0... thankx