CVS导出&&自定义Attribute的使用

1.cvs导出：List转为byte[]

    /// <summary>
    ///  CvsExport帮助类
    /// </summary>
    public static class CvsExportHelper
    {
        /// <summary>
        /// Creates the CSV from a generic list.
        /// </summary>;
        /// <typeparam name="T"></typeparam>;
        /// <param name="list">The list.</param>;
        public static byte[] CreateCSVFromGenericList<T>(List<T> list)
        {
            if (list == null || list.Count == 0) return null;


            //get type from 0th member
            Type t = list[0].GetType();
            string newLine = Environment.NewLine;
            MemoryStream output = new MemoryStream();
            using (var sw = new StreamWriter(output, new UTF8Encoding(true)))// 用true来指定包含bom
            {
                //make a new instance of the class name we figured out to get its props
                object o = Activator.CreateInstance(t);
                //gets all properties
                PropertyInfo[] props = o.GetType().GetProperties();

                //foreach of the properties in class above, write out properties
                //this is the header row
                foreach (PropertyInfo pi in props)
                {
                    var attributes = pi.GetCustomAttributes(false);
                    var columnMapping = attributes
                        .FirstOrDefault(a => a.GetType() == typeof(CSVColumnAttribute));
                    if (columnMapping != null)
                    {
                        var mapsto = columnMapping as CSVColumnAttribute;
                        sw.Write(mapsto.Name + ",");
                    }
                    else
                    {
                        sw.Write(pi.Name + ",");
                    }
                }
                sw.Write(newLine);

                //this acts as datarow
                foreach (T item in list)
                {
                    //this acts as datacolumn
                    foreach (PropertyInfo pi in props)
                    {
                        //this is the row+col intersection (the value)
                        string whatToWrite =
                            Convert.ToString(item.GetType()
                                                 .GetProperty(pi.Name)
                                                 .GetValue(item, null))
                                .Replace(',', ' ') + ',';

                        sw.Write(whatToWrite);

                    }
                    sw.Write(newLine);
                }
                sw.Flush();
            }
            byte[] bytesInStream = output.ToArray(); // simpler way of converting to array
            output.Close();
            return bytesInStream;
        }
    }

2.前端调用（网页：内存导出）

        /// <summary>
        ///  CSV Export
        /// </summary>
        /// <param name="r"></param>
        /// <returns></returns>
        [HttpPost]
        [ActionName("CSVExport")]
        public ActionResult CSVExport(ExportDSVRequest r)
        {
            string fileName = string.Format("CRMInfo-{0}.csv", Guid.NewGuid().ToString());
            byte[] result = null;
            if (string.IsNullOrWhiteSpace(r.JsonData)) {
               return Redirect("~/report/list");//返回上一页
            }

            var billsResult = JsonHelper.DeserializeJsonToList<AccountDailyMarginCSV>(r.JsonData);
 
            result = CvsExportHelper.CreateCSVFromGenericList(billsResult);
            return File(result, "text/csv", fileName);
        }    

导出至特定路径

            string fileName = string.Format("CRMInfo-{0}.csv", Guid.NewGuid().ToString());
            string content = log.ToString();
            string dir = Directory.GetCurrentDirectory();
            string fullName = Path.Combine(dir, fileName);
            if (File.Exists(fullName)) File.Delete(fullName);
            using (FileStream fs = new FileStream(fullName, FileMode.CreateNew, FileAccess.Write))
            {
                StreamWriter sw = new StreamWriter(fs, Encoding.Default);
                sw.Flush();
                sw.Write(content);
                sw.Flush();
                sw.Close();
            }    

　　

自定义attribute

    /// <summary>
    /// CSV列名Attribute
    /// </summary>
    public class CSVColumnAttribute : Attribute
    {
        /// <summary>
        /// Name
        /// </summary>
        public string Name { get; }
        /// <summary>
        /// set name
        /// </summary>
        /// <param name="name"></param>
        public CSVColumnAttribute(string name)
        {
            this.Name = name;
        }
    }

attribute使用：对List<T>中的T设置列名