c# Operation on CSV file (write, read, modify)

public static void SaveCSV(DataTable dt, string fullPath)//Table data is written to csv{
   fi = new (fullPath);
  if (!)
  {
    ();
  }
   fs = new (fullPath, , 
    );
   sw = new (fs, .UTF8);
  string data = "";
 
  for (int i = 0; i < ; i++)//Write column name  {
    data += [i].();
    if (i <  - 1)
    {
      data += ",";
    }
  }
  (data);
 
  for (int i = 0; i < ; i++) //Write data in each row  {
    data = "";
    for (int j = 0; j < ; j++)
    {
      string str = [i][j].ToString();
      str = ("\"", "\"\"");//Replace the English colon. The English colon needs to be replaced with two colons.      if ((',') || ('"')
        || ('\r') || ('\n')) //Including commas, colon, line breaks, need to be put into quotes      {
        str = ("\"{0}\"", str);
      }
 
      data += str;
      if (j <  - 1)
      {
        data += ",";
      }
    }
    (data);
  }
  ();
  ();
}

public static DataTable OpenCSV(string filePath)//Return table after reading data from csv{
   encoding = GetType(filePath); //;//
  DataTable dt = new DataTable();
   fs = new (filePath, , 
    );
 
   sr = new (fs, encoding);
 
  //Record one row of records read each time  string strLine = "";
  //Record the content of each field in each row of records  string[] aryLine = null;
  string[] tableHead = null;
  //Display the number of columns  int columnCount = 0;
  //Sign whether it is the first line of read  bool IsFirst = true;
  //Read data in CSV line by line  while ((strLine = ()) != null)
  {
    if (IsFirst == true)
    {
      tableHead = (',');
      IsFirst = false;
      columnCount = ;
      //Create a column      for (int i = 0; i < columnCount; i++)
      {
        DataColumn dc = new DataColumn(tableHead[i]);
        (dc);
      }
    }
    else
    {
      aryLine = (',');
      DataRow dr = ();
      for (int j = 0; j < columnCount; j++)
      {
        dr[j] = aryLine[j];
      }
      (dr);
    }
  }
  if (aryLine != null &&  > 0)
  {
     = tableHead[0] + " " + "asc";
  }
 
  ();
  ();
  return dt;
}
/// Given the path of the file, read the binary data of the file, and judge the encoding type of the file/// <param name="FILE_NAME">File path</param>/// <returns> File encoding type</returns> 
public static  GetType(string FILE_NAME)
{
   fs = new (FILE_NAME, , 
    );
   r = GetType(fs);
  ();
  return r;
}
 
/// Determine the encoding type of the file through the given file stream/// <param name="fs">File Stream</param>/// <returns> File encoding type</returns>public static  GetType( fs)
{
  byte[] Unicode = new byte[] { 0xFF, 0xFE, 0x41 };
  byte[] UnicodeBIG = new byte[] { 0xFE, 0xFF, 0x00 };
  byte[] UTF8 = new byte[] { 0xEF, 0xBB, 0xBF }; //With BOM   reVal = ;
 
   r = new (fs, );
  int i;
  ((), out i);
  byte[] ss = (i);
  if (IsUTF8Bytes(ss) || (ss[0] == 0xEF &amp;&amp; ss[1] == 0xBB &amp;&amp; ss[2] == 0xBF))
  {
    reVal = .UTF8;
  }
  else if (ss[0] == 0xFE &amp;&amp; ss[1] == 0xFF &amp;&amp; ss[2] == 0x00)
  {
    reVal = ;
  }
  else if (ss[0] == 0xFF &amp;&amp; ss[1] == 0xFE &amp;&amp; ss[2] == 0x41)
  {
    reVal = ;
  }
  ();
  return reVal;
}
 
/// Determine whether it is UTF8 format without BOM/// &lt;param name="data"&gt;&lt;/param&gt;
/// &lt;returns&gt;&lt;/returns&gt;
private static bool IsUTF8Bytes(byte[] data)
{
  int charByteCounter = 1;　 // Calculate the number of bytes that should still exist in the character being analyzed.  byte curByte; //The bytes currently analyzed.  for (int i = 0; i &lt; ; i++)
  {
    curByte = data[i];
    if (charByteCounter == 1)
    {
      if (curByte &gt;= 0x80)
      {
        //Judge the current        while (((curByte &lt;&lt;= 1) &amp; 0x80) != 0)
        {
          charByteCounter++;
        }
        //If the first bit of the mark is not 0, it starts with at least 2 1s, such as: 110XXXXX............1111110X        if (charByteCounter == 1 || charByteCounter &gt; 6)
        {
          return false;
        }
      }
    }
    else
    {
      //If it is UTF-8, the first position must be 1      if ((curByte &amp; 0xC0) != 0x80)
      {
        return false;
      }
      charByteCounter--;
    }
  }
  if (charByteCounter &gt; 1)
  {
    throw new Exception("Unexpected byte format");
  }
  return true;
}

public static bool ChangeFileName(string OldPath, string NewPath) 
{
  bool re = false;
  try 
  {
    if ((OldPath)) 
    {
      (OldPath, NewPath);
      re = true;
    }
  }
  catch 
  {
    re = false;
  }
  return re;
}

public static bool SaveCSV(string fullPath,string Data)
{
  bool re = true;
  try
  {
    FileStream FileStream = new FileStream(fullPath, );
    StreamWriter sw = new StreamWriter(FileStream, .UTF8);
    (Data);
    //Clear the buffer    ();
    //Close the flow    ();
    ();
  }
  catch 
  {
    re = false;
  }
  return re;
}