Help! Probleme pour ecrire dans un fichier

       public void WriteLine(string chemin, string Content, int Line)
        {
            int LineToWrite;
            int i;
            string ContentToWrite;
            string CurrentContent;
            string[] stringArray = new string[1500];
            string che = Path.GetFullPath(chemin);

            i = 0;
            ContentToWrite = Content;
            LineToWrite = Line;

            System.IO.StreamWriter file = new System.IO.StreamWriter(@che);

            CurrentContent = GiveLine(@che, i + 1);

            // On lis pour mettre les lignes du fichier dans un tableau
            while (CurrentContent != null)
            {
                CurrentContent = GiveLine(@che, i + 1);
                stringArray[i] = CurrentContent;
                i++;       
            }

            i = 0;

            // Ensuite on restitue toutes les lignes dans ce fichier, puis on ferme
            while (stringArray[i] != null)
            {
                file.WriteLine(stringArray[i]);
                i++;
            }

            // A la fin
            file.Close();
        }

Main.TraiteText.WriteLine(@"Content\Infos\infos.txt", "no", 2);

public void WriteLine(string chemin, string Content, int Line)
{
  string CurrentContent;
  ArrayList stringArray = new ArrayList();
  string che = Path.GetFullPath(chemin);

  // On lit pour mettre les lignes du fichier dans une liste
  int i = 0;
  CurrentContent = GiveLine(@che, i + 1);
  while (CurrentContent != null)
  {
    stringArray.Add(CurrentContent);
    CurrentContent = GiveLine(@che, i + 1);
    i++;       
  }

  // Ensuite on restitue toutes les lignes dans ce fichier, puis on ferme
  System.IO.StreamWriter file = new System.IO.StreamWriter(@che);
  foreach (String str in stringArray)
  {
    file.WriteLine(str);
  }

  // A la fin
  file.Close();
}

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

namespace Client_HORION
{
    class TextClass
    {
        // lire
        public string GiveLine(string chemin, int line)
        {
            int counter = 1;
            string CurrentLine;
            string che = Path.GetFullPath(chemin);

            // Read the file and display it line by line.
            System.IO.StreamReader file = new System.IO.StreamReader(@che);
            while ((CurrentLine = file.ReadLine()) != null)
            {
                if (counter == line)
                {
                    file.Close();
                    break;
                }
                counter++;
            }
            return CurrentLine;
        }

        // ecrire
        public void WriteLine(string chemin, string Content, int Line)
        {
            string CurrentContent;
            string ContentToWrite = Content;
            int LineToWrite = Line;
            ArrayList stringArray = new ArrayList();
            string che = Path.GetFullPath(chemin);

            // On lit pour mettre les lignes du fichier dans une liste
            int i = 1;
            CurrentContent = GiveLine(@che, 1);
            while (CurrentContent != null)
            {
                stringArray.Add(CurrentContent);
                CurrentContent = GiveLine(@che, i);
                i++;
            }

            // Ensuite on restitue toutes les lignes dans ce fichier, puis on ferme
            System.IO.StreamWriter file = new System.IO.StreamWriter(@che);

            i = 1;
            foreach (String str in stringArray)
            {
                if (LineToWrite != i)
                {
                    file.WriteLine(str);
                }
                else if (LineToWrite == i)
                {
                    file.WriteLine(ContentToWrite);
                }
                i++;
            }

            // A la fin
            file.Close();
        }

    }
}

                            // pour les infos de connexion
                            Main.TraiteText.WriteLine(@"Content\Infos\infos.txt", "no", 2);
Main.initMAP(int.Parse(this.Datas[1]));

Main.TraiteText.WriteLine(@"Content\Infos\infos.txt", "no", 2);

string[] lines = File.ReadAllLines(che);

public static void InsertLineInFile(string path, string line, int position)
{
  string[] lines = File.ReadAllLines(path);
  using (StreamWriter writer = new StreamWriter(path))
  {
    for (int i = 0; i < position; i++)
      writer.WriteLine(lines[i]);
    writer.WriteLine(line);
    for (int i = position; i < lines.Length; i++)
      writer.WriteLine(lines[i]);
  }
}

string[] lines = File.?????(path);

File.??????(supprimer tout le contenu)?????(path);

System.IO.File.WriteAllText(@"Path/foo.bar",string.Empty);