Export unicode data to CSV file

Question

Though this question is asked several times by many people, but again I cannot generate the required CSV file in a proper text. I am creating a CSV file which characters are set in Japanese language. Whenever I generate a CSV file, it is not exporting it in proper encoding. I want it to make it readable in a excel sheet. It is showing correct data while debugging and also notepad is displaying correct csv but while when I read the file from Excel, all text get messed up.

Here is my code:

private void GenerateCSV(string[][] value)
    {
        string attachment = "attachment; filename=CreatedCSV.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.Charset = "";
        HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF8;
        HttpContext.Current.Response.BinaryWrite(System.Text.Encoding.UTF8.GetPreamble());

        string delimiter = ", ";
        int length = value.GetLength(0);
        StringBuilder sb = new StringBuilder();
        for (int index = 0; index < length; index++)
            sb.AppendLine(string.Join(delimiter, value[index]));

        HttpContext.Current.Response.Write(sb.ToString());
        HttpContext.Current.Response.End();
    }

I tried implementing unicode too but it also did not help. What am I missing here?

Excel file looks like this:

While the notepad displays data correctly as below:

Answer 1

Your source string might be incorrectly encoded. We used your code and it works with special characters but our string builder is encoded in UTF8 using this code:

byte[] buffer = Encoding.UTF8.GetBytes(DataFeedCSV.ToString());

Answer 2

StringBuilder sb = new StringBuilder();
sb.Append("pröva-Testing");
sb.Append("\r\n");
var data = Encoding.UTF8.GetBytes(sb.ToString());
var result = Encoding.UTF8.GetPreamble().Concat(data).ToArray();
return File(result, "application/csv", "foo.csv");

With these lines, I think the Excel will be able to encode it using UTF-8 as it knows it is a utf8-encoded csv