public static void DownloadFile(HttpContext context, string filePath)
{
UtilLite.Guard<ArgumentNullException>(context == null);
FileInfo file = new FileInfo(filePath);
UtilLite.Guard<FileNotFoundException>(!file.Exists);
context.Response.Clear();
context.Response.Buffer = false;
context.Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(Encoding.UTF8.GetBytes(file.Name)));
context.Response.AppendHeader("Content-Length", file.Length.ToString());
context.Response.ContentType = "application/octet-stream";
context.Response.WriteFile(filePath);
context.Response.Flush();
context.Response.End();
}

public static void Range(HttpContext context, string filePath)
{
UtilLite.Guard<ArgumentNullException>(context == null);
HttpRequest Request = context.Request;
HttpResponse Response = context.Response;
Response.Clear();
Response.Buffer = false;
Response.AddHeader("Accept-Ranges", "bytes");
int bufferSize = 4096;
byte[] buffer = new byte[bufferSize];
using (FileStream stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize))
{
long p = 0L, l = stream.Length;
#region Resolve Range
string range = Request.Headers["Range"];
if (range != null)
{
//Range:bytes=1024-
//Range:bytes=1024-2048
//Range:bytes=-1024
//Range:bytes=0-512,1024-2048
int index = range.IndexOf("=");
if (index != -1)
{
string[] ranges = range.Substring(index + 1).Split(',');
if (ranges.Length > 1)
{
//not supported multipart/byterange
}
else
{
bool flag = false;
if (ranges[0].StartsWith("-"))
{
long _p, _absp;
if (long.TryParse(ranges[0], out _p) && (_absp = Math.Abs(_p)) <= l)
{
if (_p < 0)
{
p = l - _absp;
l = _absp;
flag = true;
}
}
}
else
{
ranges = ranges[0].Split('-');
if (ranges.Length == 2)
{
long _p, _l;
if (ranges[1] == string.Empty)
{
if (long.TryParse(ranges[0], out _p) && _p <= l)
{
p = _p;
flag = true;
}
}
else if (long.TryParse(ranges[0], out _p) && long.TryParse(ranges[1], out _l) && _p > 0 && _l > 0 && _p < _l && _l < l)
{
p = _p;
l = _l + 1;
flag = true;
}
}
}
if (flag)
{
Response.StatusCode = 206;
Response.AddHeader("Content-Range", "bytes " + p.ToString() + "-" + l.ToString() + "/" + stream.Length.ToString());
}
else
{
Response.StatusCode = 416; //Requested range not satisfiable
}
}
}
}
#endregion
Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(Encoding.UTF8.GetBytes(Path.GetFileName(filePath))));
Response.AddHeader("Content-Length", l.ToString());
Response.ContentType = "application/octet-stream";
stream.Position = p;
int read;
while (Response.IsClientConnected && p < l)
{
Response.OutputStream.Write(buffer, 0, read = stream.Read(buffer, 0, bufferSize));
Response.Flush();
p += read;
}
}
Response.End();
}