Visual Basic의 System.invalidOperationexception

Question

그래서 나는이 오류가 나는 여기에 System.invalidOperationexception 전체 오류가 얻을 말하는 얻을 : 포트에 대한

[Managed to Native Transition] 
Port Scan.exe!WindowsApplication1.My.MyProject.MyForms.Form1.get() 
Port Scan.exe!WindowsApplication1.My.MyApplication.OnCreateMainForm() 
    Microsoft.VisualBasic.dll!Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicatio Base.OnRun() 
Microsoft.VisualBasic.dll!Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplication Base.DoApplicationModel() 
Microsoft.VisualBasic.dll!Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplication Base.Run(string[] commandLine) 
[Native to Managed Transition] 
mscorlib.dll!System.Runtime.Hosting.ApplicationActivator.CreateInstance(System.ActivationCo ntext activationContext, string[] activationCustomData) 
    Microsoft.VisualStudio.HostingProcess.Utilities.dll!Microsoft.VisualStudio.HostingProcess.H ostProc.RunUsersAssemblyDebugInZone() 
    mscorlib.dll!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContex t executionContext, System.Threading.ContextCallback callback, object state, bool  preserveSyncCtx) 
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool preserveSyncCtx) 
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext  executionContext, System.Threading.ContextCallback callback, object state) 
mscorlib.dll!System.Threading.ThreadHelper.ThreadStart() 
[Native to Managed Transition] 

여기에 내가 컴파일하려고 코드가 그것을 스캐너

Public Class Form1 
Dim host As String 

Dim counter As Integer 
Dim portmin As Integer = TextBox3.Text 
Dim portmax As Integer = TextBox2.Text 
Private Sub Form1_Load(ByVal sender As System.Object, _ 
      ByVal e As System.EventArgs) Handles MyBase.Load 
    Button1.Enabled = False 
    'set counter explained before to 0 
    counter = 0 
End Sub 
Private Sub Timer1_Tick(ByVal sender As System.Object, _ 
     ByVal e As System.EventArgs) Handles Timer1.Tick 
    'Set the host and port and counter 
    counter = counter + 1 'counter is for the timer 
    host = TextBox1.Text 



    For port As Integer = portmin To portmax 

     If (port = portmax) Then 
      Exit For 
     End If 



     ' Next part creates a socket to try and connect 
     ' on with the given user information. 

     Dim hostadd As System.Net.IPAddress = _ 
      System.Net.Dns.GetHostEntry(host).AddressList(0) 
     Dim EPhost As New System.Net.IPEndPoint(hostadd, port) 
     Dim s As New System.Net.Sockets.Socket(_ 
     System.Net.Sockets.AddressFamily.InterNetwork, _ 
    System.Net.Sockets.SocketType.Stream, _ 
     System.Net.Sockets.ProtocolType.Tcp) 
     Try 
      s.Connect(EPhost) 
     Catch 
     End Try 
     If Not s.Connected Then 
      ListBox1.Items.Add("Port " + port.ToString + " is not open") 
     Else 
      ListBox1.Items.Add("Port " + port.ToString + " is open") 
      ListBox2.Items.Add(port.ToString) 

     End If 
     Label3.Text = "Open Ports: " + ListBox2.Items.Count.ToString 
    Next 
End Sub 

Private Sub Button1_Click(ByVal sender As System.Object, _ 
      ByVal e As System.EventArgs) Handles Button1.Click 
    'stop button 
    Timer1.Stop() 
    Timer1.Enabled = False 
    Button1.Enabled = True 
    Button2.Enabled = False 
End Sub 

Private Sub Button2_Click(ByVal sender As System.Object, _ 
    ByVal e As System.EventArgs) Handles Button2.Click 
    ListBox1.Items.Add("Scanning: " + TextBox1.Text) 
    ListBox1.Items.Add("-------------------") 
    Button2.Enabled = True 
    Button1.Enabled = False 
    Timer1.Enabled = True 
    Timer1.Start() 
End Sub 

Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged 

End Sub 

Private Sub TextBox2_TextChanged(sender As Object, e As EventArgs) Handles TextBox2.TextChanged 

End Sub 

Private Sub ListBox2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListBox2.SelectedIndexChanged 

End Sub 
End Class 

나는이 오류에 다소 당황하여 exe를 빌드 할 수 없으므로 정말 도움을 주셔서 감사합니다. 오류가 최소 및 최대 포트 번호를 허용하는 for 루프를 수행 할 때만 발생하는 것 같습니다.

Answer 1

문제는이 코드에 : 그 문 실행시

Dim portmin As Integer = TextBox3.Text 
Dim portmax As Integer = TextBox2.Text 

는, 형태가 아직 완전히 구성되지 않습니다. TextBox2 및 TextBox3은 아직 생성되지 않았습니다. 정수 값에 Nothing 참조를 지정하려고합니다. 허용되지 않습니다. 할당을 폼의 Load 이벤트로 이동하십시오. 또한 시간을내어 확인하고 해당 상자의 내용이 정수로 변환되는지 확인하십시오.