ASP.NET MVC项目中的大型CSV文件下载

Question

I need to export a really large csv file(~100MB). On the internet I found a similar code and implemented it for my case:

public class CSVExporter
{
    public static void WriteToCSV(List<Person> personList)
    {
        string attachment = "attachment; filename=PersonList.csv";
        HttpContext.Current.Response.Clear();
        HttpContext.Current.Response.ClearHeaders();
        HttpContext.Current.Response.ClearContent();
        HttpContext.Current.Response.AddHeader("content-disposition", attachment);
        HttpContext.Current.Response.ContentType = "text/csv";
        HttpContext.Current.Response.AddHeader("Pragma", "public");
        WriteColumnName();
        foreach (Person person in personList)
        {
            WriteUserInfo(person);
        }
        HttpContext.Current.Response.End();
    }

    private static void WriteUserInfo(Person person)
    {
        StringBuilder stringBuilder = new StringBuilder();
        AddComma(person.Name, stringBuilder);
        AddComma(person.Family, stringBuilder);
        AddComma(person.Age.ToString(), stringBuilder);
        AddComma(string.Format("{0:C2}", person.Salary), stringBuilder);
        HttpContext.Current.Response.Write(stringBuilder.ToString());
        HttpContext.Current.Response.Write(Environment.NewLine);
    }

    private static void AddComma(string value, StringBuilder stringBuilder)
    {
        stringBuilder.Append(value.Replace(',', ' '));
        stringBuilder.Append(", ");
    }

    private static void WriteColumnName()
    {
        string columnNames = "Name, Family, Age, Salary";
        HttpContext.Current.Response.Write(columnNames);
        HttpContext.Current.Response.Write(Environment.NewLine);
    }
}

The problem is I want to start the download before(!) the whole CSV is constructed. Why is not it working like I suppose it too and what must I change?

Answer 1

You could probably force the response to be flushed to the client by using

Response.Flush();

after each record is appended to the stream. Please refer to this article for more details:

http://support.microsoft.com/kb/812406