c# - 为什么我的 CSV 文件末尾有一百万个空字符

Question

我正在动态生成数据的 CSV 导出。为此，我获取项目的哈希集，然后逐行转换它们并将它们写入 MemoryStream，MemoryStream 又作为 FileResult 发送到客户端。问题是文件末尾有大约一百万个 NULL 字符，我猜这些字符的数量等于哈希集中的项目数量。但它们位于文件的末尾，而不是每行的末尾。

无论如何，代码是这样的:

Controller 方法:

public ActionResult ExportList(ListExportModel model)
{
  System.IO.MemoryStream ms = ls.ExportListToCsv(model,Server.MapPath("~/uploads"));
  return File(ms.GetBuffer(),"text/csv",model.MailingList.ListName + ".csv");
}

ExportListToCsv 方法

public MemoryStream ExportListToCsv(ListExportModel model, string folderpath)
{
    MemoryStream stream = new MemoryStream();
    StreamWriter writer = new StreamWriter(stream);

    writer.WriteLine(string.Join(",", model.Columns));
    var data = GetListItemsFromCsv(model.ListId, folderpath);

    XmlDocument doc = new XmlDocument();
    // Parallel.ForEach(data, (li) =>
    foreach (var li in data)
    {
        string line = "";
        foreach (var field in model.Columns)
        {
            doc.LoadXml(li.CustomFields);
            switch (field)
            {
                //our standard fields
                    case "email":
                        line += li.Email + ",";
                        break;
                    case "tel":
                        line += li.Tel + ",";
                        break;

                    default:
                        line += (doc.SelectNodes("//" + field))[0].Value + ",";
                        break;
                }
            }

            writer.WriteLine(line.TrimEnd(','));
        }
        writer.Flush();
        stream.Position = 0;
        return stream;
    }

和文件(所有虚拟数据，截图制作过程中没有真人受到伤害):

注意:无论我是否使用，我都会得到相同的结果

writer.Flush()

和

stream.Position = 0

或不

Answer 1

您正在调用 GetBuffer() 而不是 ToArray()。

参见:http://msdn.microsoft.com/en-us/library/system.io.memorystream.toarray

This method omits unused bytes in MemoryStream from the array. To get the entire buffer, use the GetBuffer method.

This method returns a copy of the contents of the MemoryStream as a byte array. If the current instance was constructed on a provided byte array, a copy of the section of the array to which this instance has access is returned. See the MemoryStream constructor for details.