How download response data excel from browser using web api

I want to download excel or pdf from browser when service call will return result data, for reporting purpose.

Following is my code

public HttpResponseMessage GetCsv(List searchEntity)

{

List obj = new List();

obj = searchEntity;

var sb = new StringBuilder();

sb.Append("CostCenterId,CostCenterName\r\n");

foreach (var record in obj)

{

sb.AppendFormat("=\"{0}\",", record.CostCenterId);

sb.AppendFormat("=\"{0}\",", record.CostCenterName);

}

HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);

result.Content = new StringContent(sb.ToString());

result.Content.Headers.Add("Allow", "GET, PUT, POST, DELETE, HEAD");

result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment"); //attachment will force download

result.Content.Headers.ContentDisposition.FileName = "RecordExport.csv";

return result;

}