在C＃中從文本文件中刪除一行

Question

我是C＃的新手，我有一個簡單的控制台應用程序，帶有validateVoters（）方法，該方法接受一個StudentID參數，將其與文本文件進行比較，然后返回適當的布爾值。 但是我希望它刪除特定的StudentID（如果存在的話），然后返回true，但是沒有從文件中刪除的通用方法，因此我在這里使用了成員推薦的方法：給我一個雙星號**的錯誤：
錯誤2
名稱'RemoveUnnecessaryLine'在當前上下文中不存在c：\\ Users \\ Hlogoyatau \\ Documents \\ Visual Studio 2010 \\ Projects \\ Ijoo \\ Ijoo \\ Program.cs 28 43 Ijoo

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

namespace SRCVotingSystem
 {

public class Program
{


    public bool validateVoter(String cisNo)
    {
        bool found = false;

        try
        {
            string[] ID = System.IO.File.ReadAllLines(@"C:\Users\Hlogoyatau\Pictures\votersRoll.txt");

            foreach (string line in ID)
            {
                //compares it against text file contents
                if (cisNo == line)
                {
                    string[] allLines= File.ReadAllLines("votersRoll.txt");
                    string[] newIDs= **RemoveUnnecessaryLine**(allLines);
                    File.WriteAllLines("votersRoll.txt", newIDs);


                    found = true;
                }
            }
        }

        catch (IOException e)
        {
            Console.WriteLine(e.ToString());
        }

        return found;
    }


    public static void Main()
    {

        Program vv = new Program();
        Console.WriteLine(vv.validateVoter("cis11-005"));
    }

   }
}

Answer 1

/* sample data in text.tx
 ID 1 asdfsdaf
 ID 2 asdfdsafasdfsadf
 ID 3 lkjasdfjsdf
*/
private static void Main(string[] args)
{
    var id = 2;
    var lines = File.ReadAllLines("C:\\temp\\text.txt");

    var remaining = lines.Where(x => !x.Contains(id.ToString())).ToArray();
    File.WriteAllLines("C:\\temp\\out.txt", remaining);
}

Answer 2

嘗試這個：

public bool validateVoter(String cisNo)
{
    bool found = false;

    try
    {
        string[] ID = System.IO.File.ReadAllLines(@"C:\Users\Hlogoyatau\Pictures\votersRoll.txt");

        for (int i = 0; i < ID.Length; i++)
        {
            string line = ID[i];
            //compares it against text file contents
            if (cisNo == line)
            {
                //Shift remaining lines up, overwriting current line
                for (int j = i; j < ID.Length - 1; j++)
                {
                     ID[j] = ID[j+1];
                }

                //Set last line to empty string
                ID[ID.Length - 1] = "";

                //Write file back to disk
                System.IO.File.WriteAllLines(@"C:\Users\Hlogoyatau\Pictures\votersRoll.txt", ID);

                found = true;

                //Exit loop after something is found
                break;
            }
        }
    }

    catch (IOException e)
    {
        Console.WriteLine(e.ToString());
    }

    return found;
}

它將讀取文件，找到匹配項后，會將剩余的行上移一行。 最后一行將被清除，然后將文件寫回到磁盤。 如果您不希望最后一行為空，則可以調整數組的大小（請參見Array.Resize ）。

Answer 3

嘗試使用LINQ

public void validateVoter(String cisNo)
{
    var newIDs = System.IO.File.ReadAllLines(@"C:\Users\Hlogoyatau\Pictures\votersRoll.txt").Where(l => l != cisNo);
    File.WriteAllLines(@"C:\Users\Hlogoyatau\Pictures\votersRoll.txt", newIDs);
}