output to text and not waiting the loop

Private Class LoopArgs()
    Public Reader As System.IO.StreamReader
    Public FILE_NAME As String
    Public StartDelegate As StartCounterDelegate
    Public Sub StartLoop()
        StartDelegate(Reader, FILE_NAME)
    End Sub
End Class 
Public Sub Loop(ByRef Reader As System.IO.StreamReader, ByRef FILE_NAME As String)
        Dim Str As String = Nothing
        Dim cari As String
        Dim objWriter As New System.IO.StreamWriter(FILE_NAME)
        While Reader.EndOfStream = False
            Str = Reader.ReadLine
            'MessageBox.Show(Str)
            'Label1.Text = "Checking : " & Str
            Try
                cari = RequestWebData(Str)
                If cari.Contains("http://www.mysite.com") Then
                    'TextBox2.Text = TextBox2.Text & Str & vbCrLf
                    objWriter.Write(Str & vbCrLf)
                    'MsgBox("Text written to file")
                End If
            Catch ex As Exception
                Label1.Text = "error"
            End Try
        End While
        objWriter.Close()
        MsgBox("selesai")
End Sub 
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim Reader As System.IO.StreamReader = My.Computer.FileSystem.OpenTextFileReader("C:\input.txt")
        Dim FILE_NAME As String = "C:\output.txt"
        Dim la As New LoopArgs
        la.Reader = Reader
        la.FILE_NAME = FILE_NAME
        la.StartDelegate = AddressOf Loop
        Dim t As Thread
        t = New Thread(AddressOf ca.StartLoop)
        t.Start()
        '\r\n 
 End Sub 

                                              

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Option Strict Off
Imports System.Net
Imports System.IO
Imports System.Threading 
Public Class Form1
    Delegate Sub StartLoopDelegate(ByVal iterations As Integer)
    Private Class LoopArgs
        Public Reader As System.IO.StreamReader
        Public FILE_NAME As String
        Public StartDelegate As StartLoopDelegate
        Public Sub StartLoop()
            StartDelegate(Reader, FILE_NAME)
        End Sub
    End Class
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load 
    End Sub
     Public Sub Loops(ByRef Reader As System.IO.StreamReader, ByRef FILE_NAME As String)
        Dim Str As String = Nothing
        Dim cari As String
        Dim objWriter As New System.IO.StreamWriter(FILE_NAME)
        While Reader.EndOfStream = False
            Str = Reader.ReadLine
            'MessageBox.Show(Str)
            'Label1.Text = "Checking : " & Str
            Try
                cari = RequestWebData(Str)
                If cari.Contains("http://www.mysite.com") Then
                    'TextBox2.Text = TextBox2.Text & Str & vbCrLf
                    objWriter.Write(Str & vbCrLf)
                    'MsgBox("Text written to file")
                End If
            Catch ex As Exception
                Label1.Text = "error"
            End Try
        End While
        objWriter.Close()
   
    End Sub 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim Reader As System.IO.StreamReader = My.Computer.FileSystem.OpenTextFileReader("C:\input.txt")
        Dim FILE_NAME As String = "C:\output.txt"
        Dim la As New LoopArgs
        la.Reader = Reader
        la.FILE_NAME = FILE_NAME
        la.StartDelegate = AddressOf Loops
        Dim t As Thread
        t = New Thread(AddressOf la.StartLoop)
        t.Start() 
    End Sub
End Class
                                              

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