如何检查文本文件中是否包含多行文本？

Question

我有这样的代码：

BeginInvoke(new Action(() => tempNamesAndTexts.ForEach(Item => textBox1.AppendText(DateTime.Now + "===> " + Item + Environment.NewLine)))); 
       foreach (string items in tempNamesAndTexts) 
       { 

         Logger.Write(items); 


       } 

一旦IM运行程序会做：Logger.Write（项目）; 然后将文本文件看起来像：

丹尼尔你好 罗恩喜 耶尔再见 乔希大家好

下一次运行程序会写入文本的即时消息相同的字符串。 我想检查一下，如果这个字符串已经存在于文本文件中，不要再写入它们，否则写入所以结果会是每次运行程序时它都会向记录器（文本文件）写入新的字符串，如果有的话。

这是记录文本文件的字符串变量：

full_path_log_file_name 

这个变量里面有：

C:\\Users\\Chocolade\\AppData\\Local\\ChatrollLogger\\ChatrollLogger\\log\\logger.txt 

这是直到这部分至极的完整代码是一部分DoWork的总是做有一次当我运行程序时：

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Windows.Forms; 
using System.Net; 
using System.IO; 
using System.Text.RegularExpressions; 
using System.Threading; 
using DannyGeneral; 

namespace ChatrollLogger 
{ 
    public partial class Form1 : Form 
    { 
     string log_file_name = @"\logger.txt"; 
     string full_path_log_file_name; 
     string path_log; 
     bool result; 
     List<string> namesAndTexts; 
     WebResponse response; 
     StreamReader reader; 
     string profileName; 
     string profileNameText; 
     string url; 
     string testingUrl; 
     int index; 
     List<string> names; 
     List<string> texts; 
     WebClient wc; 


     public Form1() 
     { 
      InitializeComponent(); 
      Logger.exist(); 
      wc = new WebClient(); 
      result = true; 
      url = "http://chatroll.com/rotternet"; 
      testingUrl = "http://chatroll.com/testings"; 
      backgroundWorker1.RunWorkerAsync(); 
      path_log = Path.GetDirectoryName(Application.LocalUserAppDataPath) + @"\log"; 
      full_path_log_file_name = path_log + log_file_name; 
     } 

     private void Form1_Load(object sender, EventArgs e) 
     { 

     } 

     private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e) 
     { 
      BackgroundWorker worker = sender as BackgroundWorker; 
      List<string> tempNamesAndTexts = new List<string>(); 
      string tempDownload = downloadContent(); 
      GetProfileNames(tempDownload); 
      GetTextFromProfile(tempDownload); 
      for (int i = 0; i < names.Count; i++) 
      { 
       tempNamesAndTexts.Add(names[i] + " " + texts[i]); 

      } 
      if (InvokeRequired) 
      { 
       BeginInvoke(new Action(() => tempNamesAndTexts.ForEach(Item => textBox1.AppendText(DateTime.Now + "===> " + Item + Environment.NewLine)))); 
       foreach (string items in tempNamesAndTexts) 
       { 

         Logger.Write(items); 
         string t = full_path_log_file_name; 

       } 
      } 

Answer 1

像这样？

string path = "test.txt"; 
string valueToWrite = "...."; 

//only write to the file, if the specified string is not already there 
if(!File.ReadLines(path).Any(l => string.Equals(l, valueToWrite))) 
{ 
    File.AppendAllText(path, valueToWrite); 
} 

Answer 2

使用File.ReadAllLines

string[] array = File.ReadAllLines("test.txt"); 
if(array.Length > 0) 
{ 
// lines exist 
}