Prevent "Not Responding" - vb.net

Question

When running code on a Form, sometimes (usually when looping) the program title displays "Not Responding" even though its still running fine.
In my case, I'm looping and filling an array > array to DataTable > DataTable to DataGridView.
example:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim ArrayNew(1000001, 2) As Object
For i = 0 To 1000000
For j = 0 To 1
ArrayNew(i, j) = "TEST"
Next j
Next i
Table1 = New DataTable("EXAMPLETABLE")
Table1.Columns.Add("COLUMN1")
Table1.Columns.Add("COLUMN2")
Table1.Columns.Add("COLUMN3")
Dim RowNo As Integer = 0
Do
Table1.Rows.Add(New String() {RowNo + 1, ArrayNew(RowNo, 0), ArrayNew(RowNo, 1)})
RowNo = RowNo + 1
Loop Until ArrayNew(RowNo, 1) = ""
DataGridView1.DataSource = Table1
End Sub
I read somewhere that I should be using threads? or BackgroundWorker but I'm unsure how to use these here like a lot of questions point to BackgroundWorker Class.
But I don't understand C#.

Answer 1

The first thing to do is to drop a BackgroundWorker component onto the form. Click on the component and setup handlers for the DoWork, RunWorkerCompleted, and ProgressChanged events. Then, assuming you use all the default names, your code will look like this:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
backgroundWorker1.RunWorkerAsync()
End Sub
Private Sub backgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles backgroundWorker1.DoWork
Dim worker As BackgroundWorker = DirectCast(sender, BackgroundWorker)
Dim Table1 As New DataTable("EXAMPLETABLE")
Table1.Columns.Add("COLUMN1")
Table1.Columns.Add("COLUMN2")
Table1.Columns.Add("COLUMN3")
Dim Size As Integer = 1000000
For i As Integer = 1 To Size
Table1.Rows.Add(New String() {i.ToString(), "Test", "Test"})
If i Mod 50 = 0 Then
worker.ReportProgress(i * 100.0 / Size) 'Report as a percentage of the total
End If
Next
e.Result = Table1
End Sub
Private Sub backgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs)
DataGridView1.DataSource = DirectCast(e.Result, DataTable)
End Sub
Private Sub backgroundWorker1_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles backgroundWorker1.ProgressChanged
'Check e.ProgressPercentage here
End Sub
This is the basic example. You can also use this to do things like report progress and make sure it's not already busy before starting it. More information (including samples in C#, but translates to VB.Net easily) is here:
https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.backgroundworker?view=netcore-3.1