先说前者：比如说你程序放在桌面上启动，但是中间你用了一个OpenFileDialog打开了E盘名为abc的文件夹下的某一个文件，那么CurrentDirectory就变成E：\abc了，所以如果你想再获取程序启动文件夹的某一个文件就没用了，但是Application.StartupPath就不会这样了，无论你中间打开了哪个盘的文件，启动路径都是在桌面那里，一直不会变。

    ''' <summary>
    ''' 获取根目录
    ''' </summary>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Shared Function GetPath() As String
        Return Application.StartupPath
        'Return System.Environment.CurrentDirectory
    End Function

    ''' <summary>
    ''' 写日志
    ''' </summary>
    ''' <param name="strStyle">操作类型</param>
    ''' <param name="strContent">操作内容</param>
    ''' <remarks></remarks>
    Public Shared Sub WriteLog(ByVal strStyle As String,ByVal strContent As String)
        Dim curDate As String = CDate(Now).ToString("yyyy-MM-dd HH:mm:ss")
        Dim path As String = GetPath() & "\log"
        If Not My.Computer.FileSystem.DirectoryExists(path) Then
            My.Computer.FileSystem.CreateDirectory(path)
        End If
        path &= "\" & CDate(curDate).ToString("yyyyMMdd") & ".txt"
        If Not My.Computer.FileSystem.FileExists(path) Then
            My.Computer.FileSystem.WriteAllText(path,String.Empty,False)
        End If

        Dim strValue As String = String.Empty
        strValue = "******************" & curDate & "**********************" & vbCrLf
        strValue &= "*************操作类型[" & strStyle & "]***************" & vbCrLf
        strValue &= "***************错误原因***************" & vbCrLf
        strValue &= strContent & vbCrLf & vbCrLf & vbCrLf
        My.Computer.FileSystem.WriteAllText(path,strValue,True)
    End Sub