Form Loads slowly in vb.net - vb.net

Question

I am currently working in ERP project on vb.net. I want to load product data in a textbox on form load. I am using autocomplete method but having a data of around 26000 the form loads slowly for 4 mins. Is there any way to avoid this or is there any way to call this function in background when the application starts?
This is my autocomplete textbox code. It works fine but it hangs alot as of the data is so large.
Private Sub pn()
Try
con = Class1.dbconn
Dim dt As New DataTable
Dim ds As New DataSet
ds.Tables.Add(dt)
Dim da As New SqlDataAdapter("select [Part Name] from
Part_Master_Download$", con)
da.Fill(dt)
Dim r As DataRow
TextBox9.AutoCompleteCustomSource.Clear()
For Each r In dt.Rows
TextBox9.AutoCompleteCustomSource.Add(r.Item(0).ToString)
Next
con.Close()
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Sub
the properties of the textbox should be set to true for autocompletetextbox

Answer 1

Don't populate the AutoCompleteCustomSource in a loop. Populate an array first and then load the list in one go with a single call to AddRange:
Dim items = dt.Rows.Cast(Of DataRow)().
Select(Function(row) CStr(row(0)).
ToArray()
TextBox9.AutoCompleteCustomSource.AddRange(items)
You should find that that speeds things up considerably. If there's still a problem with performance, we can look a bit further.
EDIT: To prove my point, I just tested the following code:
Public Class Form1
Private timer As Stopwatch
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
timer = Stopwatch.StartNew()
Dim rng As New Random
Dim a = Convert.ToInt32("a"c)
Dim z = Convert.ToInt32("z"c)
Dim items = Enumerable.Range(1, 26000).Select(Function(n) Convert.ToChar(rng.Next(a, z + 1)).ToString())
For Each item In items
TextBox1.AutoCompleteCustomSource.Add(item)
Next
End Sub
Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles Me.Shown
MessageBox.Show(timer.Elapsed.ToString())
End Sub
End Class
and the message displayed "00:03:08.3167858", i.e. just over three minutes to load the list. I then changed the Load event handler to this:
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
timer = Stopwatch.StartNew()
Dim rng As New Random
Dim a = Convert.ToInt32("a"c)
Dim z = Convert.ToInt32("z"c)
Dim items = Enumerable.Range(1, 26000).Select(Function(n) Convert.ToChar(rng.Next(a, z + 1)).ToString())
TextBox1.AutoCompleteCustomSource.AddRange(items.ToArray())
End Sub
so a single call to AddRange instead of calling Add in a loop, and the message was "00:00:00.0557427", i.e. just under 56 milliseconds. Is that better?

Answer 2

You can use paging to control the amount of returned data. Check this link for detailed examples.
Another way is to use (Task Async and await) so you won't lock your UI.
Here is a few last suggestions not related directly to the question but might help clean the code a bit:
you can skip the dataset and use the datatable directly, you don't need it for just one table.
Bind your results in the datatable to a datagridview or a combobox instead of iterating through your results and filling a textbox.
cheers