TActiveFileUpload displays a file upload field on a page. Upon postback,
the text entered into the field will be treated as the name of the file
that will be uploaded to the server. The property HasFile
indicates whether the file upload is successful. If successful, the file
may be obtained by callingsaveAs to save it at a specified place.
You can use FileName, FileType,
FileSize to get the original client-side file name,
the file mime type, and the file size information. If the upload is not
successful, ErrorCode contains the error code
describing the cause of failure.
TActiveFileUpload raises OnFileUpload event if a file is uploaded
(whether it succeeds or not).
TActiveFileUpload actually does a postback in a hidden IFrame, and then does a callback.
This callback then raises the OnFileUpload event. After the postback
a status icon is displayed; either a green checkmark if the upload is successful,
or a red x if there was an error.