Imports System.Net
Public Class Project1
 
    Private localIP As String
 
    ''' <summary>
    ''' Handles the Click event of the btnGo control.
    ''' Uses the backWorker process to look up the IP address for a given host name
    ''' </summary>
    ''' <param name="sender">The source of the event.</param>
    ''' <param name="e">The <see cref="T:System.EventArgs" /> instance containing the event data.</param>
    Private Sub btnGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGo.Click
        ' Make sure user enters a value
        If hostNameComboBox.Text = "" Then
            ' Reject blank entries
            statusLabel.Text = "Please enter a hostname!"
        Else
            ' disable buttone while processing and begin execution
            btnGo.Enabled = False
            statusLabel.Text = "Working..."
            backWorker.RunWorkerAsync(hostNameComboBox.Text)
        End If
 
    End Sub
 
    ''' <summary>
    ''' Handles the DoWork event of the backWorker control.
    ''' Fesolves a given hostname passed through the e parameter into its IP address.
    ''' </summary>
    ''' <param name="sender">The source of the event.</param>
    ''' <param name="e">The <see cref="T:System.ComponentModel.DoWorkEventArgs" /> instance containing the event data.</param>
    Private Sub backWorker_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles backWorker.DoWork
backWorker.ReportProgress(0)
        Try
            ' Attempt to resolve the IP address
            localIP = Dns.GetHostEntry(e.Argument).AddressList(0).ToString
 
            ' If the host name does not exist, inform the user through the result string
        Catch ex As Sockets.SocketException
            localIP = ex.Message
        End Try
backWorker.ReportProgress(100)
    End Sub
 
    ''' <summary>
    ''' Handles the RunWorkerCompleted event of the backWorker control.
    ''' Displays the result of the IP address lookup in a messagebox.
    ''' </summary>
    ''' <param name="sender">The source of the event.</param>
    ''' <param name="e">The <see cref="T:System.ComponentModel.RunWorkerCompletedEventArgs" /> instance containing the event data.</param>
    Private Sub backWorker_RunWorkerCompleted(ByVal sender As System.Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles backWorker.RunWorkerCompleted
        statusLabel.Text = "Done!"
        MessageBox.Show(localIP, "IP Address", MessageBoxButtons.OK)
        btnGo.Enabled = True
    End Sub
 
    ''' <summary>
    ''' Handles the Load event of the Project1 control.
    ''' Sets input focus to the prefilled combobox for user input of the hostname.
    ''' </summary>
    ''' <param name="sender">The source of the event.</param>
    ''' <param name="e">The <see cref="T:System.EventArgs" /> instance containing the event data.</param>
    Private Sub Project1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.hostNameComboBox.SelectAll()
        Me.hostNameComboBox.Focus()
    End Sub
 
    ''' <summary>
    ''' Handles the ProgressChanged event of the backWorker control.
    ''' Updates the progressBar based on percentage of job done.
    ''' </summary>
    ''' <param name="sender">The source of the event.</param>
    ''' <param name="e">The <see cref="T:System.ComponentModel.ProgressChangedEventArgs" /> instance containing the event data.</param>
    Private Sub backWorker_ProgressChanged(ByVal sender As System.Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles backWorker.ProgressChanged
        progressBar.Value = e.ProgressPercentage
    End Sub
End Class

BackWorker.WorkerReportsProgress = True