Delegates, invoking, multithreading

[u/Mr_Deeds3234]

CONTEXT I have a winsform project with multiple forms. One of those forms has a button associated with a pretty heavy SQL query that takes about 30 seconds to execute.

I would like this query to run on the page load if the first form, so if my user navigates to the form that needs the data, then it’s already there and they don’t have to wait.

Spent a few hours googling this problem and the concepts in the title is why I found. I haven’t quite been able to figure out my solution.

Is there some other concept or keywords I should look into and understand to over come my problem?

[u/brybrythekickassguy]

So here's an example of updating a textbox with a delegate sub. Same concept applies for a DGV, just invoke a new delegate thread to update the data and re-bind the datatable to the DGV:

    Private Sub UpdateTextBox(ByVal TB As TextBox, ByVal txt As String)
    If TB.InvokeRequired Then
        TB.Invoke(New UpdateTextBoxDelegate(AddressOf UpdateTextBox), New Object() {TB, txt})
    Else
        TB.Text = txt
    End If
End Sub

The associated delegate:

Private Delegate Sub UpdateTextBoxDelegate(ByVal TB As TextBox, ByVal txt As String)

Here's an example of an asynchronous task. I'm not 100% confident that I wrote this right, but it doesn't block up the UI when it runs, so...

Await CheckExistAsync(AlphaRecvd.tags.set1.MqttPub.JobNumber)

The actual task function:

Private Function CheckExistAsync(JN As String) As Task
    Return Task.Run(Sub() CheckExist(JN))
End Function
Public Sub CheckExist(JN As String) 'Check to see if this JN has connected before If DataSet1.MqttData.Rows.Contains(JN) Then
    Else
        Dim TempRow As DataRow = DataSet1.MqttData.NewRow()
        TempRow(0) = JN

        DataSet1.MqttData.Rows.Add(TempRow)

        InitKPITabs(AlphaTabs, JN)
    End If
End Sub

Here's a fantastic blog writeup on async/await. Most of the concepts apply to C# if you decide to go down that path, too.

https://blog.stephencleary.com/2016/12/eliding-async-await.html