Web API : List to csv file download

StringHelper.cs

public static string CreateCSVTextFile<T>(List<T> data)
{
var properties = typeof(T).GetProperties();
var result = new StringBuilder();

var header = properties.Select(x => x.Name).Select(z => StringToCSVCell(z));
var headerline = string.Join(",", header);
result.AppendLine(headerline);

foreach (var row in data)
{
var values = properties.Select(p => p.GetValue(row, null))
.Select(v => StringToCSVCell(Convert.ToString(v)));
var line = string.Join(",", values);
result.AppendLine(line);
}

return result.ToString();
}

private static string StringToCSVCell(string str)
{
bool mustQuote = (str.Contains(",") || str.Contains("\"") || str.Contains("\r") || str.Contains("\n"));
if (mustQuote)
{
StringBuilder sb = new StringBuilder();
sb.Append("\"");
foreach (char nextChar in str)
{
sb.Append(nextChar);
if (nextChar == '"')
sb.Append("\"");
}
sb.Append("\"");
return sb.ToString();
}

return str;
}

DownloadController.cs (API Controller)

[HttpGet]
[Route("down")]
public HttpResponseMessage down(int id)
{
HttpResponseMessage result = null;

try
{
using (var repo = new SomeRepository())
{
var some= repo.All.ToList(); ;

if (some!= null)
{
result = new HttpResponseMessage(HttpStatusCode.OK);

var csvString = StringHelper.CreateCSVTextFile<Some>(risk);
byte[] byteArray = Encoding.ASCII.GetBytes(csvString);
MemoryStream stream = new MemoryStream(byteArray);

result.Content = new StreamContent(stream);

result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
result.Content.Headers.ContentDisposition.FileName = string.Format("some_{0}.csv", id);
}
}
}
catch (Exception e)
{
var errorResponse = new HttpResponseMessage(HttpStatusCode.InternalServerError);
errorResponse.Content = new StringContent(e.Message);
return errorResponse;
}

return result;
}
}