覆盖文本文件里的数据

Question

大家好！
  现有一采集卡能够连续的采集数据，并把采集的数据保存到aaa.txt的文档里。
现在我想：aaa.txt这个文档只保存2000个数据，就是说第2001到第4000个数据覆盖前2000个数据，后2000个数据覆盖前2000个数据，只显示最新采集到的2000个数据，我该怎么写呢？？谢谢大家了
以下是连续连续扫描按钮的c#代码：
private void button1_Click(object sender, EventArgs e)  //连续扫描
        {
            a = true;
            timer1.Enabled = true;
           
            if (!File.Exists(path))
            {
                // Create a file to write to.
                fs = File.CreateText(path);
             }
// Open the file to read from.
            else
            {
                fs = File.AppendText(path);
            }谢谢

Answer 1

如果你的2000个指的是字节，那就直接用FileStream写入byte，当文件指针到2000了就回0即可，如果2000是行数，那么用StreamWrite类来操作即可。

Answer 2

谢谢楼上。
文档里是2000行 double型数据，还是不太会用StreamWrite类来操作，楼上帮写一下呗

Answer 3

给你一段测试代码，看懂了就应该会写了：            string path = "c:\\test.txt";
            double value = 0;
            int line = 0;
            StreamWriter sw = new StreamWriter(path);
            for (int i = 0; i < 8100; i++)
            {
                if (++line == 2000)
                {
                    sw.Flush();
                    line = 0;
                    sw.BaseStream.Seek(0, SeekOrigin.Begin);
                }
                value = i;
                sw.WriteLine(value);
            }
            sw.Flush();
            sw.Close();

Answer 4

采集卡主框架程序mainform.csusing System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Collections;namespace MainForm
{
    public partial class MainForm : Form
    {
        private SortedList SortedListRecvData;
        private SortedList SortedListRecvGrphData;
        int nProgress;
        private long nKey;
       
        public MainForm()
        {
            SortedListRecvData = new SortedList();
            SortedListRecvGrphData = new SortedList();
            InitializeComponent();
            mTranUdp = new UdpClass.TranUdp();
            mTranUdp.InitTranUdp();
            mTranUdp.TranUdpReceivedDataEvent += new UdpClass.TranUdp.TranUdpEventHandler(Recv);
            setCtl1.TranUdEventpSentDataEvent += new SetCtl.SetCtl.TranUdEventpSentHandler(mTranUdp.SentData);
            setCtl1.DataChangEvent += new SetCtl.SetCtl.DataChangHandler(DataChang);
            nProgress = 0;
        }
        public void DataChang(string sc ,string sd)
        {
            try
            {
                if (sc == "AidIP")
                {
                    mTranUdp.Udp1.sRemoteIp = sd;                }
                else if (sc == "AidPort")
                {
                    mTranUdp.Udp1.nRemotePort = Convert.ToInt32(sd);
                }
                else if (sc == "SrcIP")
                {
                    mTranUdp.Udp1.sLocalIp = sd;
                }
                else if (sc == "SrcPort")
                {
                    mTranUdp.Udp1.nLocalPort = Convert.ToInt32(sd);
                }
            }
            catch
            { }
        }
        public void Recv(long nCmd, long[] Data)
        {
            nKey = (nKey+1)& 0xffff;
           /* lock (SortedListRecvData)
            {
                 SortedListRecvData.Add(((nKey <<16)+(nCmd & 0xffff)), Data);
            }*/
            if (nCmd == 0x1111)
            {
                lock (SortedListRecvData)
                {
                    SortedListRecvGrphData.Add(((nKey << 16) + (nCmd & 0xffff)), Data);                }
                //picCtl1.UdpStatetoolStripStatusLabel.Text = "等待数据... ...";
                //picCtl1.UdptoolStripProgressBar.Value = 0;
                nProgress = 0;
            }
            else if (nCmd == 0x1212)
            {
                //picCtl1.UdpStatetoolStripStatusLabel.Text = "等待数据... ...";
                //picCtl1.UdptoolStripProgressBar.Value = (int)nKey % 160;
                nProgress = (int)nKey;
            }
            else
            {
                lock (SortedListRecvData)
                {
                    SortedListRecvData.Add(((nKey << 16) + (nCmd & 0xffff)), Data);
                }
            
            }            //timer1.Enabled = true;
            //this.timer1.Tick += new System.EventHandler(this.timer1_Tick);
            //timer1.Start();
        }
        private void timer1_Tick(object sender, EventArgs e)
        {
            long nCmd;
            long nKey;
            long[] Data;
            //timer1.Enabled = false;
            picCtl1.UdptoolStripProgressBar.Value = (int)nProgress % 160;
            if (SortedListRecvData != null || SortedListRecvData.Count != 0)
            {
                for (; ; )// (int i = 0; i < SortedListRecvData.Count; i++)
                {
                    lock (SortedListRecvData)
                    {
                        if (SortedListRecvData.Count == 0) break;
                        nCmd = ((long)SortedListRecvData.GetKey(0)) & 0x00ffff;
                        nKey = ((long)SortedListRecvData.GetKey(0)) >> 16 & 0x00ffff;
                        Data = (long[])SortedListRecvData.GetByIndex(0);                        SortedListRecvData.RemoveAt(0);
                        //SortedListRecvData.Clear();
                    }
                    setCtl1.RecvData(nCmd, Data);
                }
            }
            if (SortedListRecvGrphData != null || SortedListRecvGrphData.Count != 0)
            {
                for (; ; )// (int i = 0; i < SortedListRecvData.Count; i++)
                {
                    lock (SortedListRecvGrphData)
                    {
                        if (SortedListRecvGrphData.Count == 0) break;
                        nCmd = ((long)SortedListRecvGrphData.GetKey(0)) & 0x00ffff;
                        nKey = ((long)SortedListRecvGrphData.GetKey(0)) >> 16 & 0x00ffff;
                        Data = (long[])SortedListRecvGrphData.GetByIndex(0);                        // SortedListRecvGrphData.RemoveAt(0);
                        SortedListRecvGrphData.Clear();
                    }                    if (nCmd == 0x1111)
                    {
                        picCtl1.RecvData(nCmd, Data);
                        picCtl1.UdptoolStripProgressBar.Value = 0;
                        picCtl1.UdpTimetoolStripStatusLabel.Text = System.DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");                    }/*
               else if (nCmd == 0x1212)
                {
                    picCtl1.UdpStatetoolStripStatusLabel.Text = "等待数据... ...";                    picCtl1.UdptoolStripProgressBar.Value =(int) nProgress%160;
                    
                }*/
                }
            }
        }                private void MainForm_Load(object sender, EventArgs e)
        {        }
        
        
        
    }
}