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

        /// <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);
        }    

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