Programmatically upload file to SharePoint Document Library

Method 1 :

Stream fStream = upfile.PostedFile.InputStream;

                            byte[] contents = new byte[fStream.Length];

                            fStream.Read(contents, 0, (int)fStream.Length);

                            fStream.Close();

                            string Filename = upfile.FileName;

                            string destUrl = SPContext.Current.Site.Url + "/" + myLibrary.Title + "/" + Filename;

                            oweb.Files.Add(destUrl, contents);

Method 2 : with metadata

SPDocumentLibrary myLibrary = oweb.Lists[attachmentsLib] as SPDocumentLibrary;

                            byte[] fileBytes = upfile.FileBytes;

                            string strDestUrl = myLibrary.RootFolder.Url + "/" + upfile.FileName;

                            SPFile destFile = myLibrary.RootFolder.Files.Add(strDestUrl, fileBytes, true);

                            destFile.Item["DocID"] = "1";                           

                            destFile.Update();

                            destFile.Item.Update();

                            destFile.Update();

                            oweb.AllowUnsafeUpdates = false;