Re: Memory Leak ? - C# Discussion Boards

Xmen Real 5-Feb-09 2:32

5-Feb-09 2:32

musefan wrote:
Thou using image.fromfile() makes that files readonly and can be a pain when doing any deleting functions

what do you mean ?

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musefan5-Feb-09 2:46

5-Feb-09 2:46

I fount that having code such as

Image image = Image.FromFile("C:\\pic.png");

meant that while that image was in memory, the file could not be deleted. Appears to be a reference to the actually file (or something)

Maybe im mistaken but im pretty sure that was an issue

My opinion is... If someone has already posted an answer, dont post the SAME answer

Tom Deketelaere5-Feb-09 2:50

Tom Deketelaere

5-Feb-09 2:50

musefan wrote:
Maybe im mistaken but im pretty sure that was an issue

No your not mistaken.

Image.fromfile keeps the file locked until the object is disposed off.

Ran into this when I was displaying an image in a picture box with this function. Ended up using the stream method like you said.

musefan5-Feb-09 2:52

5-Feb-09 2:52

Thank you for the good, simple explaination of what i was trying to get at Smile | :)

My opinion is... If someone has already posted an answer, dont post the SAME answer

Xmen Real 5-Feb-09 2:52

5-Feb-09 2:52

musefan wrote:
Appears to be a reference to the actually file

hehe no, I think it does the same thing as stream. Will you tell what was the thing that made you think that ?

musefan5-Feb-09 2:55

5-Feb-09 2:55

I found:

using .FromFile() causes problems and
using .FromStream() did not cause problems

what more can i say, i didnt need to look into it anymore

My opinion is... If someone has already posted an answer, dont post the SAME answer

Xmen Real 5-Feb-09 2:59

5-Feb-09 2:59

okay, see that was just a little part of my class. Actually im reading the images like this

BL = new Bitmap(new MemoryStream(tmp_br.ReadBytes(tmp_br.ReadInt32())));

Since i wrote that code(in first post) in CodeProject, so i thought to write Image.FromFile()

Rob Philpott5-Feb-09 2:53

Rob Philpott

5-Feb-09 2:53

No it won't leak as such. You have to try pretty hard to get .NET to leak properly.

Image is disposable though, so you might want to dispose of images when you're done with them otherwise they might hang around longer than you want. (that'd release the file too).

Regards,
Rob Philpott.

musefan5-Feb-09 2:57

5-Feb-09 2:57

yeah i went down the dispose route at first when using .FromFile() but found it more hassle then creating one function that returns an Image from a stream by passing the filepath

My opinion is... If someone has already posted an answer, dont post the SAME answer

Xmen Real 5-Feb-09 3:01

5-Feb-09 3:01

yes

http://www.codeproject.com/script/Forums/View.aspx?fid=1649&msg=2912374

C# controls, .Net components. Help Desk Software

MadArtSoft5-Feb-09 5:09

MadArtSoft

5-Feb-09 5:09

Try use Using keyword. It will dispose object. Read more in MSDN about Using keyword.

how to send user ID across differnet application in ASP.Net?

George_George5-Feb-09 2:02

Re: how to send user ID across differnet application in ASP.Net?

5-Feb-09 2:02

Hello everyone,

I have two web applications all are developed by ASP.Net. Now I want to provide a feature which enables the user to click from one URL in application site (one virtual directory of IIS) A to the other URL in application site B (another virtual directory of IIS).

I have two ideas to implement them, but both of them have issues. I want to know what solution should be optimum solution?

Solution 1: using cookie, so from both application sites, we could retrieve user ID information from reading cookie, but I am afraid if cookie is disabled in browser, this "jump" feature never works.

Solution 2: When the user redirects to an URL in another site, I could append user ID after the URL, I could redirect to this URL in another site http://www.anotherapplicationsite.com/somesuburl?userID=foo, but I am afraird that in this way userID will be exposed easily which raise security issues.

Any advice?

thanks in advance,
George

J4amieC5-Feb-09 2:23

J4amieC

5-Feb-09 2:23

George_George wrote:
Solution 1

Wont work, cookies are only sent to the same domain that created them for obvious security reasons. If both applications resided within the same domain but were, say, subdirectories of that main root then your in with a chance of this solution!

George_George wrote:
Solution 2

Is terribly insecure how you described it.

If you have to do it this way, you need to generate something long (like a Guid) for each session and pass this between apps. You MUST make sure these sessions are time limited, and cannot be used after a session has finished. This is no small feat, and requires alot of bespoke code to handle session management, and the criteria for which they can acceptably be passed between 2 apps.

One other solution you could consider is using NT Security in both applications, as the currently logged on user is easy to obtain in ASP.NET or a winforms app - this would negate the need for much of your user management code, and allow you to still know who is currently logged in. This solution kind of relies on your applications residing on one network, where all users can be added to your domain server(s).

You're getting better at asking questions my old friend Wink | ;)

This one showed some actual though (and maybe a little research) on your part OMG | :OMG:

Re: how to send user ID across differnet application in ASP.Net?

musefan5-Feb-09 2:36

Re: how to send user ID across differnet application in ASP.Net?

5-Feb-09 2:36

Could you not just create a hash of the (userID + logginDateTimeString) and store that in database along with an expiary DateTime? - Thats fairly simple

My opinion is... If someone has already posted an answer, dont post the SAME answer

J4amieC5-Feb-09 2:43

J4amieC

5-Feb-09 2:43

Simple, but fairly easyto brute-force from an (in)security point of view.

Re: how to send user ID across differnet application in ASP.Net?

musefan5-Feb-09 2:50

Re: how to send user ID across differnet application in ASP.Net?

5-Feb-09 2:50

then throw in a salt value. it would take a while to brute force attack it anyway.

plus the only valuable info in the hash would be a userID value i.e. 1, 34 or 103 which is useless if it cannot be used anywhere. no?

My opinion is... If someone has already posted an answer, dont post the SAME answer

George_George7-Feb-09 1:37

Re: how to send user ID across differnet application in ASP.Net?

7-Feb-09 1:37

"then throw in a salt value. it would take a while to brute force attack it anyway." -- intersted in this, could you show me what do you mean salt value please? Smile | :)

happy weekend,
George

musefan9-Feb-09 2:30

Re: how to send user ID across differnet application in ASP.Net?

9-Feb-09 2:30

a salt is basically just a static string that you append to other information before hashing

i.e.

string salt = "SALTVALUE";
string password = "PASSWORD";

string combined = salt + password;

Hash(Combined);

now the hashed value is not simply the password, so it makes it harder to crack

My opinion is... If someone has already posted an answer, dont post the SAME answer

George_George7-Feb-09 1:36

Re: how to send user ID across differnet application in ASP.Net?

7-Feb-09 1:36

Then what is your better solution?

regards,
George

George_George7-Feb-09 1:36

Re: how to send user ID across differnet application in ASP.Net?

7-Feb-09 1:36

Good solution, musefan!

regards,
George

George_George7-Feb-09 1:35

Re: how to send user ID across differnet application in ASP.Net?

7-Feb-09 1:35

Thanks J4amieC,

One more question about your reply, "If both applications resided within the same domain but were, say, subdirectories of that main root then your in with a chance of this solution!" -- what do you mean this? Could you show me a sample please? Sorry I read a couple of times but can not understand what do you mean.

For other parts of your reply, they are so great and I think I understand. Smile | :)

regards,
George

musefan5-Feb-09 2:24

Re: how to send user ID across differnet application in ASP.Net?

5-Feb-09 2:24

Cookies are not difficult to expose either thou so... what about when a user logs in you create a random key and store that on the server so you can identify the user. That could be passed in the URL and would be different each time

Ive never done it, so just a suggestion.

My opinion is... If someone has already posted an answer, dont post the SAME answer

George_George7-Feb-09 1:39

Re: how to send user ID across differnet application in ASP.Net?

7-Feb-09 1:39

Cool, musefan!

"Cookies are not difficult to expose either thou" -- could you show me more information please? Any documents or your experience proves some ways to expose cookie information?

regards,
George

musefan9-Feb-09 2:33

Re: how to send user ID across differnet application in ASP.Net?

9-Feb-09 2:33

well you can use the WebBrowser control, then view the cookies with the following

WebBrowser.Document.Cookie //this is a string of cookies for the loaded page, they are split with ;

My opinion is... If someone has already posted an answer, dont post the SAME answer

Xmen Real 5-Feb-09 2:25