C# 读写文件的工具类

主要包含解析文件，读具体几行，向后插入行，重新覆盖文件等方法

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Collections;

namespace pregnancy_autoupdate.utils
{
    class TxtUtil
    {
        private   int   _LineNumber; 
        private   string   _FilePath; 

        ///   <summary> 
        ///   文件总行数 
        ///   </summary> 
        public   int   LineNumber 
        { 
        get{return   this._LineNumber;} 
        } 

        ///   <summary> 
        ///   文件路径 
        ///   </summary> 
        public   string   FilePath 
        { 
        get{return   this._FilePath;} 
        } 

        private   ArrayList   fileLine;

        /// <summary>
        /// 读取文件到ArrayList里面去，按照行号排列 
        /// </summary>
        /// <param name="FilePath"></param>
        public TxtUtil(string FilePath)
        {
            this._FilePath = FilePath;
            StreamReader sr = new StreamReader(new FileStream(FilePath, FileMode.OpenOrCreate), Encoding.GetEncoding("UTF-8"));
            fileLine = new ArrayList();
            int i = 0;
            while (sr.Peek() > -1) {
                fileLine.Insert(i,sr.ReadLine());
                i = i + 1;
            
            }
            this._LineNumber = i;
            sr.Close();
        }

        ///   <summary> 
        ///   返回某一行的内容 
        ///   </summary> 
        ///   <param   name= "LineIndex "> </param> 
        ///   <returns> </returns> 
        public string ReadLine(int LineIndex)
        {
            return this.fileLine[LineIndex].ToString();
        }

        public List<String> readLastLineContent(int lastLineNumber) 
        {
            List<String> contents = new List<String>();
            int start = 0;
            int end = this._LineNumber - 1;
            if (lastLineNumber < this._LineNumber)
            {
                end = lastLineNumber - 1;

            }
            for (int i = start; i <= end; ++i)
            {
                contents.Add(ReadLine(i));
            }
            return contents;
        }

        ///   <summary> 
        ///   拿最后几行的数据，如果总行数不够，就拿文件的所有内容
        ///   </summary> 
        public List<LogTxt> readLastLineLogTxt(int lastLineNumber)
        {
            List<LogTxt> logTxts = new List<LogTxt>();
            int start = this._LineNumber - 1;
            int end = 0;
            if (lastLineNumber < this._LineNumber)
            {
                end = this._LineNumber - lastLineNumber;

            }
             for (int i = start; i >= end; --i)
                {
                    string content = ReadLine(i);
                    string[] ss = content.Split('#');
                    string logDate = ss[0];
                    string logConent = ss[1];

                    LogTxt logTxt = new LogTxt();
                    logTxt.LogDateTime = Convert.ToDateTime(logDate);
                    logTxt.LogContent = logConent;

                    logTxts.Add(logTxt);
                }
            return logTxts;
        }


        ///   <summary> 
        ///   插入某行到某处 
        ///   </summary> 
        public void InsertLine(int LineIndex, string LineValue)
        {
            if (LineIndex <= this._LineNumber)
            {
                this.fileLine.Insert(LineIndex, LineValue);
            }
            else
            {
                this.fileLine.Insert(this._LineNumber, LineValue);
                this._LineNumber += 1;
            }
        }

        ///   <summary> 
        ///   插入最后一行数据
        ///   </summary> 
        public void InsertLine(string LineValue)
        {
            this.fileLine.Insert(this._LineNumber, LineValue);
            this._LineNumber += 1;
        }

        ///   <summary> 
        ///   覆盖原文件 
        ///   </summary> 
        public void Save()
        {
            StreamWriter sw = new StreamWriter(this._FilePath);
            for (int i = 0; i < this.fileLine.Count; i++)
            {
                sw.WriteLine(this.fileLine[i]);
            }
            sw.Close();
        } 


    }
}