How to download a CSV file from an ASP page after user clicks a button

Question

I basically have put the following into my button click even handler, and it works mostly but it also writes out all the html of the page too in the CSV file. Is there a way to stop this?

                    StringBuilder sb = new StringBuilder();
                sb.AppendLine("pkey,epsn,Cal. Date (UTC),Va Mult, Vb Mult, Vc Mult,Ia Mult, Ib Mult, Ic Mult, Ia Phase, Ib Phase, Ic Phase, CT Rating, CT Type, Cal By");
                Response.ContentType = "application/csv";

                Response.AddHeader("content-disposition", "attachment; filename=EPSn.csv");
                Response.Write(sb.ToString());
                foreach (DataRow row in dt.Rows)
                {
                    sb = new StringBuilder((string)row[0]);
                    for (int i = 1; i < dt.Columns.Count; i++)
                    {
                        if (row[i] is DBNull)
                            sb.Append(",NULL");
                        else if (i == 2)
                            sb.Append("," + new DateTime((long)row[i]).ToString("G"));
                        else
                            sb.Append("," + row[i].ToString());

                    }
                    sb.AppendLine();
                    Response.Write(sb.ToString());

score 2 · Answer 1 · edited May 23 '17 at 12:04

2

Before you start to write the response add.

Response.Clear();

Add the following at the end of your code.

Response.Flush();
Response.End();

Kudos the the following question about the best way to end the response.

HttpResponse.End vs HttpResponse.Close vs HttpResponse.SuppressContent

edited May 23 '17 at 12:04

Community

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1

answered Jun 26 '12 at 21:06

Chris Diver

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score 1 · Accepted Answer · answered Jun 26 '12 at 21:03

1

I think you should also have Response.End() after this code: So that no more response is added to the response stream. That may be adding page output to your CSV.

sb.AppendLine();
Response.Write(sb.ToString());

Response.End();

answered Jun 26 '12 at 21:03

bdoshi

1,051
12
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score 0 · Answer 3 · answered Jun 26 '12 at 20:51

0

Is there a way to stop this?

You could clear the response:

Response.Clear();
Response.ClearContent();

Also please stop rolling your own CSV parser. It's absolutely horrible, I see people continue doing this mistake over and over again.

answered Jun 26 '12 at 20:51

Darin Dimitrov

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sorry I should have added that line, but I do have a response.Clear above the string builder declaration. – Matthew Sanford Jun 26 '12 at 20:52
Also try adding `Response.ClearContent();`. – Darin Dimitrov Jun 26 '12 at 20:54
I added that above the StringBuilder declaration, and that did not work either. – Matthew Sanford Jun 26 '12 at 20:55
btw Technically I am not rolling my own, CSV parser, Excel is going to parse it. Im just writing it. – Matthew Sanford Jun 26 '12 at 21:10
Yeah, that's the whole problem. You are writing/rolling it :-) And CSV parser doesn't only mean reading. It also includes writing. So whether you are using `string.Split(',')` or `sb.Append(",")` you are equally guilty :-) – Darin Dimitrov Jun 26 '12 at 21:11

score 0 · Answer 4 · answered Jun 26 '12 at 20:57

I don't know if you're trying to avoid excel, but this snippet works in my code:

    void InitAttachment()
    {
        string attachment = "attachment; filename= " + this.FileName;
        Response.ClearContent();
        Response.AddHeader("content-disposition", attachment);
        Response.ContentType = "application/excel";
    }

How to download a CSV file from an ASP page after user clicks a button

4 Answers4