Question

I am trying to start a thread in a form for a function that takes about 5 seconds to run so I can keep the UI from locking up. I have the following code below, but it fails when it hits “thread1.start.” When I watch it though a debugger it just goes strait to “End Sub” and it does not go to the getSecurityStuff() method that I am expecting it to go to. Any ideas?

Thanks!

Imports System.Threading

Public Class frmAddAssets

    Private theDict As Dictionary(Of String, String) = Nothing


    Private Sub frmAddAssets_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

        Control.CheckForIllegalCrossThreadCalls = False

    End Sub

    Private Sub cmbTickerEntry_Leave(sender As System.Object, e As System.EventArgs) Handles cmbTickerEntry.Leave

        Dim thread1 As New Thread(New ThreadStart(AddressOf getSecurityStuff))

        thread1.Start()

    End Sub

    Public Sub getSecurityStuff()

        Dim getData As New clsSecurityView(cmbTickerEntry.Text())

        Try
            theDict = getData.getStockData()
        Catch ex As Exception
            Throw
        End Try

        filldata()

    End Sub

    Private Sub filldata()

        Dim list As New List(Of String)(theDict.Keys)

        txtTicker.Text = cmbTickerEntry.Text.ToString()

        For Each kvp As KeyValuePair(Of String, String) In theDict

            Select Case True
                Case kvp.Key = "Name"
                    txtSecurityName.Text = kvp.Value.ToString()
                Case kvp.Key = "Price"
                    txtPrice.Text = kvp.Value.ToString()
                Case kvp.Key = "Market Capitalization"
                    txtMarketCap.Text = kvp.Value.ToString()
                Case kvp.Key = "Dividend Yield"
                    txtDivYield.Text = kvp.Value.ToString()
                Case kvp.Key = "PE Ratio"
                    txtPERatio.Text = kvp.Value.ToString()
                Case kvp.Key = "EPS"
                    txtEPS.Text = kvp.Value.ToString()
            End Select

        Next

    End Sub
End Class

Answer 1

…When I watch it though a debugger it just goes strait to “End
Sub”…

Please note that thread1.Start() won’t block the current thread.

Setting CheckForIllegalCrossThreadCalls to False won’t do anything, but ignore the exception(s) that’s throwen, when you access the properties of a control owned by the UI thread – which also is your problem:

• You create a new thread
• The new thread calls getSecurityStuff
• You try to declare a new clsSecurityView, with cmbTickerEntry.Text as parameter.
• EXCEPTION – you try to access a control owned by the UI thread, while being on another thread!
• No exception shows up, because you’ve set CheckForIllegalCrossThreadCalls to False

Same deal with fillData… trying to access controls outside the UI thread.

Solution: Use Invoke/BeginInvoke to execute code that should read/modify properties on controls owned by the UI thread.