边读边计算的如果用计数器则可以指定读取第几行内容第一例(答复:咨询VB读文本文件，文本文件有N行，3列。想得到1、2列相同时。3列的值求和)http://bbs.csdn.net/topics/390

Dim 文件路径 As String = System.Environment.CurrentDirectory + "\新建文本文档.txt"
        Dim 内容 As New List(Of String), 暂存 As String = ",,1", 计算 As String()
        If New FileInfo(文件路径).Exists Then
            Dim 打开 As New FileStream(文件路径, FileMode.Open)
            Dim 读取 As New StreamReader(打开)
            Dim 判断 = 0
            While (读取.EndOfStream <> True)
                Dim 取值 = 读取.ReadLine()
                判断 += 1
                If (暂存.Split(",")(0) <> 取值.Split(",")(0)) Or (暂存.Split(",")(1) <> 取值.Split(",")(1)) Then
                    If 判断 > 1 Then
                        内容.Add(暂存)
                    End If
                    暂存 = 取值
                Else
                    计算 = 取值.Split(",")
                    计算(2) = (Int16.Parse(计算(2)) + Int16.Parse(暂存.Split(",")(2))).ToString
                    内容.Add(String.Join(",", 计算))
                    判断 = 0
                End If
            End While
        End If