下面是文件内数据：
30,100,50
20,100,10
10,50,10
读取上面的文件后，写成下面的形式：
30,100,50
20,10
10,50

也就是说，上一行和下一行的数据如果相同，就不写，怎么来判断这个过程

说的不清楚，在来举个例子
读取下面的数
100,50,60
100,20,30
因为第二行也有100，所以写的时候
100,50,60  
20,30   ‘第一行已经有100，第二行就不写了，
怎么实现这个分析判读的过程，跪求！

怎么没人回复，给个提示也行啊

版主，给点思路吧

貌似版主不在，，我也急着等他的意见呢。。。

你的题目说得不是很清晰，我读出了点意思。下面是我给的一点分析思路。
一，你先声明个数组把已经有的数据进行存储。
二，for 循环   把新进来的数据和原先已经有的数据进行比较。用If语句进行判断，比较。控制输出


我不是很明白你说的意思就不提供代码了，怕浪费资源了。如果要补充再看看吧。

谢谢楼上的兄弟

不知道你的数据源于何处，又要写道哪里？说清楚了可以给你一段代码。

版主来了，谢谢，数据来自记事本，热盼！！！

现学现卖，查了一下帮助，把1楼的数据存到记事本里，编了如下代码，供参考吧。
在窗体上放了两个Listbox控件和一个按钮控件
Imports System
Imports
Public Class Form2
    Private Sub Main()
        Try
            Using sr As StreamReader = New StreamReader("D:\VS编程\读写文件.txt")
                Dim line As String
                Do
                    line = sr.ReadLine()
                    ListBox1.Items.Add(line)
                    Console.WriteLine(line)
                Loop Until line Is Nothing
                sr.Close()
            End Using
        Catch E As Exception
            Console.WriteLine("不能读取文件！")
            Console.WriteLine(E.Message)
        End Try
    End Sub

    Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Main()
        Dim STR0 As String
        Dim J As Integer = ListBox1.Items.Count - 1
        Dim AA(J, 2), BB(J, 2) As String
        For I As Integer = 0 To J
            STR0 = ListBox1.Items(I)
            AA(I, 0) = Mid(STR0, 1, InStr(STR0, ",") - 1)
            STR0 = Mid(STR0, InStr(STR0, ",") + 1)
            AA(I, 1) = Mid(STR0, 1, InStr(STR0, ",") - 1)
            AA(I, 2) = Mid(STR0, InStr(STR0, ",") + 1)
        Next
        BB(0, 0) = AA(0, 0)
        BB(0, 1) = AA(0, 1)
        BB(0, 2) = AA(0, 2)
        For I As Integer = 1 To J
            BB(I, 0) = IIf(AA(I, 0) = AA(I - 1, 0), "", AA(I, 0))
            BB(I, 1) = IIf(AA(I, 1) = AA(I - 1, 1), "", AA(I, 1))
            BB(I, 2) = IIf(AA(I, 2) = AA(I - 1, 2), "", AA(I, 2))
        Next
        For I As Integer = 0 To J
            STR0 = BB(I, 0) + IIf(BB(I, 1).Length > 0, "," + BB(I, 1), "") + IIf(BB(I, 2).Length > 0, "," + BB(I, 2), "")
            ListBox2.Items.Add(STR0)
        Next
    End Sub
End Class

根据sywzs版主代码，我也来凑个热闹

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim i As Integer = 0 '用于计数，从第二行开始比对
        Dim t As Integer = 0
        Dim a() As String '用于记录上一行的字符
        Dim b() As String '用于记录当前行的字符
        Dim bSame As Boolean = False '判定是否在上一行有相同的
        Dim newstring As String = "" '用于输出筛选后的字符
        Try
            Using sr As StreamReader = New StreamReader("D:\1.txt")
                Dim line As String
                Do
                    newstring = "" : ReDim b(0) : bSame = False '每次读取一行前初始化变量值
                    line = sr.ReadLine()

                    t = UBound(line.Split(","))
                    For j As Integer = 0 To t
                        ReDim Preserve b(j)
                        b(j) = line.Split(",")(j)
                    Next
                    i = i + 1
                    If i > 1 Then '从第二行开始比对
                        For j = 0 To b.Count - 1
                            bSame = False
                            For k = 0 To a.Count - 1
                                If a(k) = b(j) Then
                                    bSame = True
                                    Exit For
                                End If
                            Next
                            If bSame = False Then newstring = newstring & b(j) & ","
                        Next

                        Console.WriteLine(newstring.Substring(0, newstring.Length - 1)) '输出结果到.net的输出窗口
                    Else
                        Console.WriteLine(line)'输出结果到.net的输出窗口
                    End If

                    a = b '比对结束后，将数组B赋值给A，便于下一行比对
                Loop Until line Is Nothing
                sr.Close()

            End Using
        Catch Ex As Exception
            Console.WriteLine("不能读取文件！")
            Console.WriteLine(Ex.Message)
        End Try


    End Sub
End Class