C# Discussion Boards - CodeProject

Re: string vs. String; (string) casting vs. ToString()

16-Jul-02 22:01

overbored wrote:
string and String?

nothing Smile | :)

Same as int = Int32, short = Int16 , bool = Boolean, etc. MSDN defines them as aliases.

overbored wrote:
casting a value using (string) and using ToString()?

The ToString() method allow programmers to have a friendly text definition of an object. EG font.ToString() will return all the font's parameters, name, etc. Purely informational, where a (string) object wont be allowed unless the object is a string or a string cast has been implemented (not sure on how you would do this).

Hope this helps Smile | :)

READ MSDN

jparsons17-Jul-02 3:51

jparsons

17-Jul-02 3:51

leppie wrote:
Purely informational, where a (string) object wont be allowed unless the object is a string or a string cast has been implemented (not sure on how you would do this).

You can do this with the implicit and explicit operators. Here is a small bit of code that will allow a class to be implicitly cast to a string.

<br />
public static implicit operator string(MyClass c) {<br />
  return c.ToString();<br />
}<br />

This will allow for the implicit conversion of MyClass to a string. If you want to force people to explicitly cast to a String then change the keyword to explicit instead of implicit

Jared
jparsons@jparsons.org
www.prism.gatech.edu/~gte477n

Re: string vs. String; (string) casting vs. ToString()

Mazdak17-Jul-02 9:17

Mazdak

17-Jul-02 9:17

String mostly used in ASP.NET I think.And convert to string there. Unsure | :~

Mazy

"If I go crazy then will you still
Call me Superman
If I’m alive and well, will you be
There holding my hand
I’ll keep you by my side with
My superhuman might
Kryptonite"Kryptonite-3 Doors Down

File Verifying

Nnamdi Onyeyiri16-Jul-02 21:16

16-Jul-02 21:16

I am making a download class, kinda ambitious, considering I know little, but, at the moment, it supports paused/resume downloads, and saving the state of the downloads, so the program ccan be shut down, and the downloads will carry on when iots started up again. anyway, i am trying to add support for multiple downlioad locations, and i want to be able to generate a checksum, or something, for the remote file, and the local file, so that i can verify if the file was downloaded successfully, but i do not know how, any help, or pointers in the right direction?

Suspicious | :suss: Email: theeclypse@hotmail.com URL: http://www.onyeyiri.co.uk
"All programmers are playwrights and all computers are lousy actors."

leppie16-Jul-02 22:32

16-Jul-02 22:32

Nnamdi Onyeyiri wrote:
i want to be able to generate a checksum, or something, for the remote file,

Thats not really possible unless you own the internet Smile | :)

I assume you want somethin similar to eDonkey's file hashing to prevent corrupted downloads. Unless you can control the other side, you cant get a checksum.

I also presume you want somethin similar to GetRight's Segmented downloading. Most programs doing this, creates a blank file to the size (from the returned HTTP header) of the downloaded file, then writes to the file byte by byte.

You can easily run a "scan" thru the file to see what is still needed. Also by changing the header sent u can resume most files if the server supports partial content (see below).

Nnamdi Onyeyiri wrote:
i am trying to add support for multiple downlioad locations

In your your Download class change the "URL" property to URL[]. Or if you dont have somethin like that, you might want to create it to keep track of other variables like speed, pingtime and availability. Also note that you will need to make sure each download location has exactly the "same" file by comparing the sizes. Also , you need to make sure that the remote file's date hasnt changed (incase file size is the same) when resuming the download, although some servers might create the file on the fly to prevent leeching Frown | :(

Hope this all helps Smile | :)

Example of header sent for partial content:

!!!! ----Header Sent----
>>>> GET /Downloads/MagicInstall.msi HTTP/1.1
Host: www.dotnetmagic.com
Range: bytes=23232-
User-Agent: Mozilla/4.0 (compatible; MSIE 5.0; Windows 98)
Accept: */*
If-Range: Fri, 12 Jul 2002 18:28:00 GMT

Example of header recieved for partial content:

!!!! ----Header Recv----
HTTP/1.1 206 Partial Content
Date: Wed, 17 Jul 2002 08:19:38 GMT
Server: Apache
Last-Modified: Fri, 12 Jul 2002 18:28:00 GMT
ETag: "1441e9-8b600-3d2f1fb0"
Accept-Ranges: bytes
Content-Length: 547648
Content-Range: bytes 23232-570879/570880
Content-Type: text/plain

READ MSDN

Nnamdi Onyeyiri17-Jul-02 0:10

17-Jul-02 0:10

i was actually gonna do it by doing all the checking and stuff like that.

but for the segmenting, i was gonna allocate each server a section of the file to download, then get them to download to seperate files, then combine the files to one at the end, i was not sure how to get them all to write to the same file at once. Big Grin | :-D

Suspicious | :suss: Email: theeclypse@hotmail.com URL: http://www.onyeyiri.co.uk
"All programmers are playwrights and all computers are lousy actors."

leppie17-Jul-02 0:45

17-Jul-02 0:45

Nnamdi Onyeyiri wrote:
i was not sure how to get them all to write to the same file at once.

Try referencing them all to the same filestream, you will be writing a byte buffer (say 4kb) at any one time, using a lock to prevent (or rather queue) the other threads from writing to the stream at the same time.

READ MSDN

Nnamdi Onyeyiri17-Jul-02 0:53

17-Jul-02 0:53

gd idea, BUT, the bytes may not be written in order.

Suspicious | :suss: Email: theeclypse@hotmail.com URL: http://www.onyeyiri.co.uk
"All programmers are playwrights and all computers are lousy actors."

leppie17-Jul-02 1:06

17-Jul-02 1:06

the byte buffer will be written to the file sequencially , you will just need to keep track of the start offset where it should be written in the file for each thread Smile | :)

READ MSDN

Nnamdi Onyeyiri17-Jul-02 2:01

17-Jul-02 2:01

ahh i see now.....thanks, ill have a crack at that. if i get it working [ fingers crossed ] ill make an article on it. Smile | :)

Suspicious | :suss: Email: theeclypse@hotmail.com URL: http://www.onyeyiri.co.uk
"All programmers are playwrights and all computers are lousy actors."

leppie17-Jul-02 2:32

17-Jul-02 2:32

If got problems, send me the source as I just created a need to have a class like that as well Smile | :)

Cheers

Good Luck

READ MSDN

Nnamdi Onyeyiri17-Jul-02 2:34

17-Jul-02 2:34

leppie wrote:
If got problems, send me the source as I just created a need to have a class like that as well

a download class?

Suspicious | :suss: Email: theeclypse@hotmail.com URL: http://www.onyeyiri.co.uk
"All programmers are playwrights and all computers are lousy actors."

leppie17-Jul-02 3:19

17-Jul-02 3:19

Yes

, something that I want to integtrate into an IRC client i am writing.

READ MSDN

Nnamdi Onyeyiri17-Jul-02 4:02

17-Jul-02 4:02

im not writing a program per say, more of im just writing misc classes, and putting them into a dll, for use in future projects.

Suspicious | :suss: Email: theeclypse@hotmail.com URL: http://www.onyeyiri.co.uk
"All programmers are playwrights and all computers are lousy actors."

leppie17-Jul-02 10:20

17-Jul-02 10:20

Thats what i meant Smile | :)

Then I wont have to write it Smile | :)

and I can maybe help you better it if neccesary Smile | :)

I am almost 80% complete with my IRC client and HTTP transfer is one of the funtionalities I would like to implement as a plugin to my client, as well as FTP and some file sharing protocols.

Give me a shout then when done please Smile | :)

Cheers

READ MSDN

Nnamdi Onyeyiri17-Jul-02 0:11