//引用：
//using System.Text;
//using System.IO;

/// <summary>
/// 写文件
/// </summary>
/// <param name="path">文件路径</param>
/// <param name="context">内容</param>
public void WriteFile(string path, string context)
{
    using (FileStream fs = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write))
    {
        fs.Write(new byte[] { 239, 187, 191 }, 0, 3); //UTF8 BOM:EF BB BF

        byte[] info = new UTF8Encoding(true).GetBytes(context);
        fs.Write(info, 0, info.Length);
    }
}

/// <summary>
/// 读文件
/// </summary>
/// <param name="path">文件路径</param>
/// <returns></returns>
public string ReadFile(string path)
{
    StringBuilder sb = new StringBuilder();

    using (FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read))
    {
        //用此方法读取后直接写入时，新文件和原文件可能不一致
        //byte[] b = new byte[1024];
        //UTF8Encoding temp = new UTF8Encoding(true);
        //while (fs.Read(b, 0, b.Length) > 0)
        //{
        //    sb.Append(temp.GetString(b));
        //}
        byte[] b = new byte[fs.Length];
        UTF8Encoding temp = new UTF8Encoding(true);
        fs.Read(b, 0, b.Length);
        sb.Append(temp.GetString(b));
    }

    return sb.ToString();
}