public class CsvFileResult<T> : FileResult where T : class
    {
        private IEnumerable<T> _data;
        public CsvFileResult(IEnumerable<T> data)
            : base("text/CSV")
        {
            _data = data;
        }
        protected override void WriteFile(HttpResponseBase response)
        {
            var maxLine = int.Parse(ConfigurationManager.AppSettings["csvExport:MaxLine"]);
            int count = 0;
            var outPutStream = response.OutputStream;
            using (var streamWriter = new StreamWriter(outPutStream, System.Text.Encoding.UTF8))
            using (var writer = new CsvWriter(streamWriter))
            {
                writer.WriteHeader<T>();
                foreach (var item in _data)
                {
                    writer.WriteRecord(item);
                    count++;
                    if (count % 50 == 0)
                    {
                        streamWriter.Flush();
                        response.Flush();
                    }
                    if (count >= maxLine)
                    {
                        break;
                    }
                }
            }
        }
    }
实现依赖于CSVHelper
ASP.NET MVC 导出CSV 的 CsvFileResult 类
原文:http://blog.csdn.net/lan_liang/article/details/43678931