' 导入命名空间
Imports System.IO
Imports System.Text

Public Class Test
  Public Shared Sub Main()
    Dim path As String = "c:\temp\MyTest.txt"

    If Not File.Exists(path) Then
      ' Create a file to write to. 
      Using sw As StreamWriter = File.CreateText(path)
        sw.WriteLine("Hello")
        sw.WriteLine("And")
        sw.WriteLine("Welcome")
      End Using
    End If

    ' Open the file to read from. 
    Using sr As StreamReader = File.OpenText(path)
      Do While sr.Peek() >= 0
        Console.WriteLine(sr.ReadLine())
      Loop
    End Using

  End Sub
End Class

' 导入命名空间
Imports System
Imports System.IO

public class LogTest
   public Shared Sub Main
        MyLog.Log("Started Up", "C:\test.txt")
        MyLog.Log(String.Format("DisplayName called, {0} {1} output","B", "A"), "C:\test.txt")
   End Sub
End class

Public Class MyLog
    Const DefaultLogFile As String = "C:\LogFile.txt"

    Shared Sub Log(ByVal Message As String,ByVal FileName As String)
        Dim objLogFile As StreamWriter
        
        If IO.File.Exists(FileName) Then
            objLogFile = File.AppendText(FileName)
        ElseIf Directory.Exists (Path.GetDirectoryName(FileName)) Then
            objLogFile = File.CreateText(FileName)
        Else
            objLogFile = File.AppendText(DefaultLogFile)
        End If

        objLogFile.WriteLine(Message)
        objLogFile.Flush()
        objLogFile.Close()
    End Sub
End Class