C#文件流下载文件

1，推荐指数*****，大文件也可以

string fileName = "test.pdf";
string filePath = Server.MapPath("/" + fileName);
Response.ContentType = "application/octet-stream";
Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
Response.TransmitFile(filePath);

2，推荐指数****

string fileName = "test.pdf";
string filePath = Server.MapPath("/" + fileName);
FileInfo fileInfo = new FileInfo(filePath);
Response.Clear();
Response.ClearContent();
Response.ClearHeaders();
Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
Response.AddHeader("Content-Length", fileInfo.Length.ToString());
Response.AddHeader("Content-Transfer-Encoding", "binary");
Response.ContentType = "application/octet-stream";//application//pdf
Response.ContentEncoding = System.Text.Encoding.GetEncoding("utf-8");
Response.WriteFile(fileInfo.FullName);
Response.Flush();
Response.End();

3、推荐指数***，大于400m的文件会卡死

string fileName = "test.pdf";
        string filePath = Server.MapPath("/" + fileName);

        FileStream fs = new FileStream(filePath, FileMode.Open);
        byte[] bytes = new byte[(int)fs.Length];
        fs.Read(bytes, 0, bytes.Length);
        fs.Close();
        Response.ContentType = "application/octet-stream";
        Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
        Response.BinaryWrite(bytes);
        Response.Flush();
        Response.End();