Re: Loading thumbnails in listview.....faster way? - C# Discussion Boards

is it possible for an hacker make this:

21-Oct-05 8:35

refer to user32.dll , import this DLL and you can capture all the key events

Re: Capture Key Events

S. Senthil Kumar21-Oct-05 20:50

S. Senthil Kumar

21-Oct-05 20:50

Can't you just set them up as accelerators for a menu or a toolbar?

Regards
Senthil
_____________________________
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Anonymous21-Oct-05 6:30

Anonymous

21-Oct-05 6:30

if i have a serialized struct object with these information:
bitmap
string
string
byte[]

can an hacker load the serialized file and see these information that is get the bitmap file, the strings...

Also:
if i've an .exe with embedded a bitmap, can he get the bitmap?

Re: is it possible for an hacker make this:

Kythen21-Oct-05 8:04

Kythen

21-Oct-05 8:04

The answer is yes to both questions. If your software can use the object or bitmap, so can anyone else through debugging and reverse engineering.

The only effective way to prevent this would be to encrypt your sensitive content and have the decryption key entered by the user. Having the software automatically decrypt the content with a key contained inside the software or system itself is no different than the original situation because anyone can just follow along and wait for your software to decrypt the content on its own.

Re: is it possible for an hacker make this:

Sasuko21-Oct-05 12:55

Sasuko

21-Oct-05 12:55

How much time do you think the hacker is able to get the key within the .exe and decrypt the file?

Loading thumbnails in listview.....faster way?

abcxyz8221-Oct-05 6:29

abcxyz82

21-Oct-05 6:29

I have windows forms application, where user can select images to be loaded from FileDialog. It creates thumbnails of those and displayes them in listview...its taking longer then expected. Users generally select 30-35 200DPI .jpeg images. I am using Imagelist & Listview combination....I think problem is of windows painting(invalidate or refresh)...I do beginUpdate,endUpdate before and after adding items.

How can i boost performance of this task?

Any help will greatly be appriciated..

Regards,
MaulikCE

Re: Loading thumbnails in listview.....faster way?

Douglas Troy21-Oct-05 6:42

Douglas Troy

21-Oct-05 6:42

1. Make sure all your images already contain an embedded Thumbnail image
2. Only load those images in the visible area (in other words, don't load them all, only what the user can see on the screen)
3. Thread it so the loading process doesn't "tag" your window

Re: Loading thumbnails in listview.....faster way?

Libor Tinka21-Oct-05 6:44

Libor Tinka

21-Oct-05 6:44

You have to save your thumbnail images and just load them next time except shrinking the original images again and again.

Thumbnails can be stored in some pre-defined directory with hashed filenames. I have developed such very standard system of storing thumbnails based on MD5 hashing. It works this way:

1. Check if the image is small enough (no need to create thumbnail => return)
2. Create MD5 hash from image's FULL path (C:\My Documents\Pictures\ ...)
3. Look to your Thumbnails directory, if there is a thumbnail created
3.1 Yes, load thumbnail
3.2 No, create thumbnail and save it in Thumbnails directory

This is my method for generating MD5 from path string (it returns MD5 in hex format):

<br />
using System.Security.Cryptography;<br />
using System.Text;<br />
<br />
...<br />
<br />
    // generate MD5 path<br />
    protected string HashPath(string path) {<br />
<br />
      ASCIIEncoding enc = new ASCIIEncoding();<br />
      MD5 md5 = MD5CryptoServiceProvider.Create();<br />
<br />
      byte[] buffer = md5.ComputeHash(enc.GetBytes(path));<br />
      string hashPath = "";<br />
<br />
      for (int i = 0; i < buffer.Length; i++)<br />
        hashPath = hashPath + String.Format("{0:X2}", buffer[i]).ToLower();<br />
<br />
      return parentPanel.hashDirectory + hashPath + ".jpg";<br />
    }<br />

...and of course, optimize your code of thumbnail creation. Use fast GDI+ filters for resampling images and put it all on background separate thread.

Hope this helps Big Grin | :-D

Check valid XML element name.

Libor Tinka21-Oct-05 6:12

Libor Tinka

21-Oct-05 6:12

How to check if the string can be a valid XML element name?

In other words, I'm looking for this kind of function:

<br />
bool XmlValidate(string name);<br />
<br />
XmlValidate("RightElement"       );   // returns true<br />
XmlValidate("2 Wrong ,@# Element");   // returns false<br />

Re: Check valid XML element name.

whizzs21-Oct-05 10:57

whizzs

21-Oct-05 10:57

I'm not sure about a validate function, but you could do it this way:

using System.Text.RegularExpressions;
.
.
.
// reg ex to validate an XML element name

Regex reg = new Regex ( @"^(?!xml)[a-zA-Z]\w+$", RegexOptions.IgnoreCase );

if ( reg.IsMatch ( "STRING TO CHECK" ) )
{
// do something with it
}

I did not verify the regular expression string against all possible errors (malformed element names), but you should be able to correct any mistakes or add characters that you want to be valid. I don't like to use anything other than what is already there.

Hope this helps

Re: Check valid XML element name.

leppie21-Oct-05 12:31

leppie

21-Oct-05 12:31

System.Xml.Serialization.CodeIdentifier.MakeValid() just check if the returned value equals the input value.

^{xacc-ide 0.0.99-preview7 now with C#, C, C++, IL, XML, Nemerle, IronPython, Perl, Caml, SML, Ruby, Flex, Yacc, Java, Javascript, Lua, Prolog and Boo highlighting support!}

Little Red 'X' on MDI

Dwayner7921-Oct-05 5:12

Dwayner79

21-Oct-05 5:12

When The RED X on the parent form is pressed, what is run? It seems like the child form_Closing runs prior to the Parent form_Closing event. I need to capture the X press before it does ANYTHING... including kill the child form. Any ideas?

Thanks

*****************
"We need to apply 21st-century information technology to the health care field. We need to have our medical records put on the I.T." —GW

-- modified at 11:12 Friday 21st October, 2005

Re: Little Red 'X' on MDI

Libor Tinka21-Oct-05 6:16

Libor Tinka

21-Oct-05 6:16

Add this simple code to your main form class:

<br />
protected override void OnClosing(CancelEventArgs cea) {<br />
<br />
  if (there are any MDIs)<br />
    cea.Cancel = true;<br />
  else<br />
    base.OnClosing(cea); // not necessary, but nice<br />
}<br />

Re: Little Red 'X' on MDI

Dwayner7921-Oct-05 7:37

Dwayner79

21-Oct-05 7:37

Great... thanks,

I think I can get the rest... will write back if not.

Cheers

*****************
"We need to apply 21st-century information technology to the health care field. We need to have our medical records put on the I.T." —GW

Beginner Help: Unassigned local variable

ivelander21-Oct-05 4:19

ivelander

21-Oct-05 4:19

Hello all, I am brand new to the C# world and am having issues with my first program. Below is the code, and I am getting an "Unassigned local variable" on the Console.Write for the finalSalary variable. Is my problem with data type, or more likely the conditional? Thanks in advance for the help, and I appologize for the simplicity of my problem!

<code>using System;

namespace EmployeeSalary
{
/// <summary>
/// Calculates employee salary based on experience, birthday, position, and company success
/// </summary>

class EmployeeSalary
{

[STAThread]
static void Main(string[] args)
{
int executive, //employee's executive status
baseSalary = 5000; //employee's base salary
finalSalary, //employee's final salary
experience, //employee's years of experience
birthday; //employee's birthday bonus

// Employee's executive status (1 = exec, 2 = not exec)
Console.Write( "Please enter executive code (1 = yes 2 = no): " );
executive = Int32.Parse( Console.ReadLine() );
if ( executive == 1 )
Console.WriteLine( "\nSorry, you're an executive, no benefits for you!" );

//Employee's years of experience (1 = less than 3 yrs, 2 = 3 to 5 yrs, 3 = over 5 yrs)
Console.WriteLine( "\nPlease enter your experience code (1 = less than 3 yrs, 2 = 3-5 yrs, 2 = over 5 yrs)" );
experience = Int32.Parse( Console.ReadLine() );
if ( experience == 1 ) finalSalary = baseSalary - 2000;
else if ( experience == 2 ) finalSalary = baseSalary + 2500;
else if ( experience == 3 ) finalSalary = baseSalary + baseSalary;
else Console.WriteLine("That is not a valid entry");

//Write final salary
Console.WriteLine(finalSalary.ToString("c"));

}
}
}</code>

Member 114619621-Oct-05 4:34

Member 1146196

21-Oct-05 4:34

The ";" at the end of code baseSalary=5000 stops the int declaration.
Add "int finalSalary=0" and your code should work fine.
Its a good practice to always add type "int" before variables

hv fun

ivelander21-Oct-05 4:41

ivelander

21-Oct-05 4:41

I knew it would be something simple. The semicolon is actually not there in my initial code, I was rearranging things after I posted it so it would be a little more clear.

I think assigning 0 to finalSalary should do the trick, thanks for the help, I'm sure I will be back for more!

Matt Gerrans21-Oct-05 16:08

Matt Gerrans

21-Oct-05 16:08

> Its a good practice to always add type "int" before variables.

WTF | :WTF:

But then it is so hard to do things like floating point math, string manipulation and all kinds of object oriented stuff. Poke tongue | ;-P

Matt Gerrans

Tom Larsen21-Oct-05 4:58

Tom Larsen

21-Oct-05 4:58

It is entirely possible that finalSalary will not be assigned a value before it is used in execution (consider if experience is not 1, 2, or 3). This is what the compiler is complaining about.

You could assign finalSalary a value right after you declare it. You could also make the else branch assign it.

Writing a Trailware for an Application

whizzs21-Oct-05 11:07

whizzs

21-Oct-05 11:07

Your problem is that it is possible in your if statement to never assign a value to finalSalary since you declared finalSalary at the beginning and did not initialize it. So if someone enters a "4" at your prompt the code will execute the final "else" statement and write out to the console "That is not a valid entry" but will continue on to the final Console.WriteLine which will try to execute with an uninitialized variable.

Visual studio is smart enough to detect when people try to initialize variables inside of "if" statements but not smart enough to know if all paths assign a valid result to the variable so it always throws a flag when you try to do this.

The answer is to do one of the following:
1) initialize the variable at instantiation
2) move the Console.WriteLine statement to inside each "if" clause that you want it to print the final salary (probably your best bet since you don't want it to write out if the users response is invalid)

Hope this helps

Samar Aarkotti21-Oct-05 4:18

21-Oct-05 4:18

I have an application that I've written using C#. I want to incorporate trialware functionality so that a user can run my program for X many days. Any suggestions on this?

I don't consider simply reading/writing to the registry an acceptable solution. Nor do I like the notion of a license file, As i am not maintaining any server. Perhaps some combination of these would prove an adequate solution.

I want to prevent the following:
1. user setting back the clock to get more free trial.
2. Uninstall - reinstall to get a new free trial
3. hacking a file or registry to turn off the trial. <- I don't think this is likely, given the intended customer base.

Thanks for your help.

Tom Larsen21-Oct-05 4:54

Tom Larsen

21-Oct-05 4:54

Read http://www.codeproject.com/dotnet/xmldsiglic.asp[^] but even this won't satisfy your requirements. In fact I don't know of any technology available that will satisfy your list for .Net Framework.

Simply put, the old mechanisms and behavior necessary to do licensing on C/C++ runtime binaries will not work for anything that uses the .Net runtime. I do not know of anything that functions like FlexLM for .Net simply because of this, although I admit I haven't looked recently either. If you want rigorous license enforcement you might want to consider using C/C++ under Win32 instead.

Samar Aarkotti21-Oct-05 5:22

21-Oct-05 5:22

thanks tom,

yes that is true, every code is hackable one way or the other.
i have looked into some of the product's out there that just do licensing. but they are very costly. but the one i liked is
www.xheo.com

thanks for the help.
Samar Aarkotti

Tom Larsen21-Oct-05 8:09

Tom Larsen

21-Oct-05 8:09

I've done a bit research on the subject where the primary problem is that even signed binaries and assemblies can be subverted to avoid any license check. That is just the nature of the .Net Framework since it doesn't obey the classic rules for binary handling. The reason why classic C/C++ can be strongly licensed is that the runtime rules are tied deeply into the OS behavior. In .Net the rules are enforced only by .Net itself and therefore are much easier to subvert.

I've mentioned this before in similar questions on the topic: The .Net Framwork is wonderful for many things but being hardened isn't one of them. If the requirement is have a hardened, highly unhackable app you need to chose some other technology.

Samar Aarkotti21-Oct-05 8:26