Cross Threading Query

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Hi am new with Threading and I want to Upgrade my Project so that when ever I Query to my Database "MySql" And "MS Sql" my UI won't hang up

I've Tried Application.DoEvent but still I want to try Threading it gives me challenge to myself

:)

so here's my Code

VB

ListView Click Event

Dim LoadQuery As New Thread(AddressOf LoadToAnotherListView)
LoadQuery.IsBackground = True
LoadQuery.Start()
CheckForIllegalCrossThreadCalls = False

VB

Public Sub LoadToAnotherListView
Dim count As Integer = 0
Using con As New SqlClient.SqlConnection(ConnectionString)
            con.Open()
            Dim Sql As String = "SELECT FirstName,LastName,MiddleName FROM contacts WHERE  Gender = @Gender AND Age = @Age"
            Using cmd As New SqlClient.SqlCommand(Sql, con)
                cmd.Parameters.AddWithValue("@Gender", ListView1.FocusedItem.Text)
                cmd.Parameters.AddWithValue("@Age", ListView1.FocusedItem.SubItems(2).Text)
                cmd.CommandTimeout = 3600
                cmd.CommandType = CommandType.Text
                Using DataRead As SqlClient.SqlDataReader = cmd.ExecuteReader
                    If DataRead.HasRows Then
                        lblLoading.Visible = False
                        While DataRead.Read
                            count += 1
                            ListView2.Items.Add(Trim(DataRead(0).ToString))
                            ListView2.Items(ListView2.Items.Count - 1).SubItems.Add(Trim(DataRead(1).ToString))
                            ListView2.Items(ListView2.Items.Count - 1).SubItems.Add(Trim(Format(DataRead(2), "yyyy-MM-dd")))
                        End While
                        lblItem.Visible = True
                        lblItem.Text = countitem & " Item/s"
                    End If
                    DataRead.Close()
                End Using
            End Using
            con.Close()
        End Using
btnPrint.Enabled = ListView2.Items.Count > 1
End Sub

How do I Implement Threading with out using
CheckForIllegalCrossThreadCalls = False
It give exemption of CrossThreading

PS: If you have better way of my coding feel free to post :)

Posted 17-Jul-13 22:45pm

iMaker.ph

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Bernhard Hiller · Answer 1 · 2013-07-18T02:43:00

Well, the point is that you try to change your ListView2 from a thread which is not the main (UI) thread - and that's not allowed at all.
A solution could be to load the data from the database into a collection object in your new thread, then signal that the data are available, and then add the data to the ListView in the main thread (use InvokeRequired and Invoke).
Another point for optimization are the BeginUpdate and EndUpdate methods of the listview. And you could eventually use the VirtualMode of the list view. Or limit the number of result items with a LIMIT 100 clause at the end of your sql statement...