public static void SaveCSV(DataTable dt, string fullPath)//table数据写入csv
{
    System.IO.FileInfo fi = new System.IO.FileInfo(fullPath);
    if (!fi.Directory.Exists)
    {
        fi.Directory.Create();
    }
    System.IO.FileStream fs = new System.IO.FileStream(fullPath, System.IO.FileMode.Create, 
        System.IO.FileAccess.Write);
    System.IO.StreamWriter sw = new System.IO.StreamWriter(fs, System.Text.Encoding.UTF8);
    string data = "";

    for (int i = 0; i < dt.Columns.Count; i++)//写入列名
    {
        data += dt.Columns[i].ColumnName.ToString();
        if (i < dt.Columns.Count - 1)
        {
            data += ",";
        }
    }
    sw.WriteLine(data);

    for (int i = 0; i < dt.Rows.Count; i++) //写入各行数据
    {
        data = "";
        for (int j = 0; j < dt.Columns.Count; j++)
        {
            string str = dt.Rows[i][j].ToString();
            str = str.Replace("\"", "\"\"");//替换英文冒号 英文冒号需要换成两个冒号
            if (str.Contains(',') || str.Contains('"')
                || str.Contains('\r') || str.Contains('\n')) //含逗号 冒号 换行符的需要放到引号中
            {
                str = string.Format("\"{0}\"", str);
            }

            data += str;
            if (j < dt.Columns.Count - 1)
            {
                data += ",";
            }
        }
        sw.WriteLine(data);
    }
    sw.Close();
    fs.Close();
}

public static DataTable OpenCSV(string filePath)//从csv读取数据返回table
{
    System.Text.Encoding encoding = GetType(filePath); //Encoding.ASCII;//
    DataTable dt = new DataTable();
    System.IO.FileStream fs = new System.IO.FileStream(filePath, System.IO.FileMode.Open, 
        System.IO.FileAccess.Read);

    System.IO.StreamReader sr = new System.IO.StreamReader(fs, encoding);

    //记录每次读取的一行记录
    string strLine = "";
    //记录每行记录中的各字段内容
    string[] aryLine = null;
    string[] tableHead = null;
    //标示列数
    int columnCount = 0;
    //标示是否是读取的第一行
    bool IsFirst = true;
    //逐行读取CSV中的数据
    while ((strLine = sr.ReadLine()) != null)
    {
        if (IsFirst == true)
        {
            tableHead = strLine.Split(',');
            IsFirst = false;
            columnCount = tableHead.Length;
            //创建列
            for (int i = 0; i < columnCount; i++)
            {
                DataColumn dc = new DataColumn(tableHead[i]);
                dt.Columns.Add(dc);
            }
        }
        else
        {
            aryLine = strLine.Split(',');
            DataRow dr = dt.NewRow();
            for (int j = 0; j < columnCount; j++)
            {
                dr[j] = aryLine[j];
            }
            dt.Rows.Add(dr);
        }
    }
    if (aryLine != null && aryLine.Length > 0)
    {
        dt.DefaultView.Sort = tableHead[0] + " " + "asc";
    }

    sr.Close();
    fs.Close();
    return dt;
}
/// 给定文件的路径，读取文件的二进制数据，判断文件的编码类型
/// <param name="FILE_NAME">文件路径</param>
/// <returns>文件的编码类型</returns>

public static System.Text.Encoding GetType(string FILE_NAME)
{
    System.IO.FileStream fs = new System.IO.FileStream(FILE_NAME, System.IO.FileMode.Open, 
        System.IO.FileAccess.Read);
    System.Text.Encoding r = GetType(fs);
    fs.Close();
    return r;
}

/// 通过给定的文件流，判断文件的编码类型
/// <param name="fs">文件流</param>
/// <returns>文件的编码类型</returns>
public static System.Text.Encoding GetType(System.IO.FileStream fs)
{
    byte[] Unicode = new byte[] { 0xFF, 0xFE, 0x41 };
    byte[] UnicodeBIG = new byte[] { 0xFE, 0xFF, 0x00 };
    byte[] UTF8 = new byte[] { 0xEF, 0xBB, 0xBF }; //带BOM
    System.Text.Encoding reVal = System.Text.Encoding.Default;

    System.IO.BinaryReader r = new System.IO.BinaryReader(fs, System.Text.Encoding.Default);
    int i;
    int.TryParse(fs.Length.ToString(), out i);
    byte[] ss = r.ReadBytes(i);
    if (IsUTF8Bytes(ss) || (ss[0] == 0xEF && ss[1] == 0xBB && ss[2] == 0xBF))
    {
        reVal = System.Text.Encoding.UTF8;
    }
    else if (ss[0] == 0xFE && ss[1] == 0xFF && ss[2] == 0x00)
    {
        reVal = System.Text.Encoding.BigEndianUnicode;
    }
    else if (ss[0] == 0xFF && ss[1] == 0xFE && ss[2] == 0x41)
    {
        reVal = System.Text.Encoding.Unicode;
    }
    r.Close();
    return reVal;
}

/// 判断是否是不带 BOM 的 UTF8 格式
/// <param name="data"></param>
/// <returns></returns>
private static bool IsUTF8Bytes(byte[] data)
{
    int charByteCounter = 1;　 //计算当前正分析的字符应还有的字节数
    byte curByte; //当前分析的字节.
    for (int i = 0; i < data.Length; i++)
    {
        curByte = data[i];
        if (charByteCounter == 1)
        {
            if (curByte >= 0x80)
            {
                //判断当前
                while (((curByte <<= 1) & 0x80) != 0)
                {
                    charByteCounter++;
                }
                //标记位首位若为非0 则至少以2个1开始 如:110XXXXX...........1111110X　
                if (charByteCounter == 1 || charByteCounter > 6)
                {
                    return false;
                }
            }
        }
        else
        {
            //若是UTF-8 此时第一位必须为1
            if ((curByte & 0xC0) != 0x80)
            {
                return false;
            }
            charByteCounter--;
        }
    }
    if (charByteCounter > 1)
    {
        throw new Exception("非预期的byte格式");
    }
    return true;
}