C#

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Cryptography Wender Oliveira29-Jul-04 9:14 Wender Oliveira 29-Jul-04 9:14  Hello people, I know that System.Security.Cryptography is a good way to protect data but now I have another problem. How to protect my private key? I can't leave may key on EXE or DLL's becaus C# is an easy way for reverse engeneering... I don't just said easy but... SO VERY MUCH EASY A LOT (lol)... What can I do to protect this? Wender Oliveira .NET Programmer Re: Cryptography Heath Stewart29-Jul-04 9:22 Heath Stewart 29-Jul-04 9:22  You wouldn't distribute your private key anyway. That's always bad no matter what you're doing. If you're looking for a way to verify data, you'll want to use digital signatures. This allows you to distribute your public key (it's public, so it doesn't really matter*) and verify the signature of the signed data (it's a digest of the signed data encrypted with your private key; RSA and DSA implement this differently). While my article probably isn't what you're looking for, read Using XML Digital Signatures for Application Licensing[^] for a good conceptual overview. If you need to encrypt data, it's often best you use services provided by the OS. If you'll always run on Windows, read How To Create a DPAPI Library[^] on MSDN. This is a handy API for storing encrypted credentials, and is used by Passport (at least the local implementation that MSN and Windows Messengers use as well as IE for web sites). It's also very customizable and does most of the work for you. If you want to implement your own encryption, generate a key pair on the machine after the app's installed. Store that in a key container. This method is fool proof, but not cryptoanalyst proof.   Microsoft MVP, Visual C# My Articles control InvokeRequired() always necessary? vista2729-Jul-04 8:32 vista27 29-Jul-04 8:32  i was under the impression that ANY time a control is accessed by a thread that didn't create the control, the call has to be marshaled to the creating thread, and .NET provides this by returning TRUE from Invoke.Required, and then using Invoke() passing it a delegate. many times i find myself forgetting to do this, and am reminded with mysterious crashes when the control is accessed from another thread. other times i forget, i am not reminded because it seems to work fine, which doesn't make sense to me. i stepped through code and confirmed that another (non-creating) thread was writing to a RichTextBox without a problem. my question is, why is this? is it just the richTExtBox that can be accessed from another thread? Re: control InvokeRequired() always necessary? Judah Gabriel Himango29-Jul-04 8:58 Judah Gabriel Himango 29-Jul-04 8:58  You can call Control.Invoke, .BeginInvoke, .EndInvoke, .CreateGraphics on any thread you please. The RTB will blow up on you eventually, though, I've seen it several times. #include "witty_sig.h" Re: control InvokeRequired() always necessary? Nick Parker29-Jul-04 9:07 Nick Parker 29-Jul-04 9:07  A flaw in .NET 1.x, which has been corrected in 2.0 beta so far. In fact you will get the following error image in Visual Studio 2005 when you try to perform such an act. Threading Error[^] - Nick Parker My Blog | My Articles Re: control InvokeRequired() always necessary? Heath Stewart29-Jul-04 9:13 Heath Stewart 29-Jul-04 9:13  Been coding with threads improperly, have we Nick? Naw, just kidding. It's good to see that VS2005 is finally doing something about what so many do wrong. I certainly hope they fix the escaped character problem, though!   Microsoft MVP, Visual C# My Articles Re: control InvokeRequired() always necessary? Nick Parker29-Jul-04 9:28 Nick Parker 29-Jul-04 9:28  Heath Stewart wrote: Been coding with threads improperly, have we Nick? Nope, just testing things out to see the difference in 2.0, isn't that what every developer is doing?? Heath Stewart wrote: I certainly hope they fix the escaped character problem, though! I'm not aware of what your talking about, can you expand? - Nick Parker My Blog | My Articles Re: control InvokeRequired() always necessary? Heath Stewart29-Jul-04 9:39 Heath Stewart 29-Jul-04 9:39  Nick Parker wrote: isn't that what every developer is doing?? No, I just compiled a simple app with one line: DoesEverything.TestAllNewAPIs(). Didn't you? Nick Parker wrote: I'm not aware of what your talking about, can you expand? Expand! Excellent choice of words, and very relevent! Look at the text in the screenshot. You'll see a lot of \r\n. They should be expanded (see what I mean) to the actual characters that they represent (0x10 and 0x13), not displayed in the text.   Microsoft MVP, Visual C# My Articles Re: control InvokeRequired() always necessary? Judah Gabriel Himango29-Jul-04 9:39 Judah Gabriel Himango 29-Jul-04 9:39  "illegal operation occurred was:\r\n\r\n\tat" #include "witty_sig.h" Re: control InvokeRequired() always necessary? Heath Stewart29-Jul-04 9:16 Heath Stewart 29-Jul-04 9:16  Is it always a good idea to use Control.Invoke and Control.InvokeRequired? Yes. Most definitely. Is it always necessary? Not always. Some things will work, but could possibly cause problems down the road. It's always a good idea to use the ISynchronizeInvoke implementation when you know that other threads will be updating controls, but you may not always see problems if you don't. This really comes down to the differences between PostMessage and SendMessage (native APIs) that are used internally (and some times you just get lucky).   Microsoft MVP, Visual C# My Articles Instantiating an array of objects crushinghellhammer29-Jul-04 8:11 crushinghellhammer 29-Jul-04 8:11  Hi, I'm facing the following problem in trying to code a DSP application in C#. I need to create an array of objects of a class "cBiquad" using its default constructor. The number of cBiquad objects is "mnNumBiquads". How do I do this? I tried the following: int mnNumBiquads = (mnOrder + 1)/2; int[] Biquad = new int[mnNumBiquads]; for (int i = 0; i < mnNumBiquads; i++) { Biquad[i] = new cBiquad(); } However, this gives me the obvious error of not being able to implicitly convert cBiquad to int. Could somebody suggest what I could do? Re: Instantiating an array of objects Nick Parker29-Jul-04 9:11 Nick Parker 29-Jul-04 9:11  crushinghellhammer wrote: Could somebody suggest what I could do? int size = 10; cBiquad[] cba = new cBiquad[size]; for(int i = 0; i < size; i++) cba[i] = new cBiquad(); - Nick Parker My Blog | My Articles Re: Instantiating an array of objects crushinghellhammer29-Jul-04 9:32 crushinghellhammer 29-Jul-04 9:32  Thanks, Nick. I *just* figured out myself, as well. cBiquad[] arrBiquads = new cBiquad[mnNumBiquads]; for (int i = 0; i < mnNumBiquads; i++) { arrBiquads[i] = new cBiquad(); } Is there a more elegant way of doing this, as in instantiating the array in just one line, using the default cBiquad constructor. I mean: cBiquad[] arrBiquads = something... Re: Instantiating an array of objects Nick Parker29-Jul-04 10:11 Nick Parker 29-Jul-04 10:11  crushinghellhammer wrote: Is there a more elegant way of doing this Nope, that's about it. You could write a class factory of sorts that would take care of this for you, depending on what you are doing that may be overhead. - Nick Parker My Blog | My Articles WM_PRINT for themed controls Mathew Hall29-Jul-04 6:31 Mathew Hall 29-Jul-04 6:31  Hi, I'm trying to get a custom control to render its contents into a bitmap by sending it a WM_PRINT message. This works great if XP themes are not enabled. If XP themes are enabled, some controls (textbox, listview, listbox, treeview, datetimepicker) forget how to draw a themed border and draw an unthemed 3d border instead - and the groupbox only draws its background Any ideas on how to get round this? "I think I speak on behalf of everyone here when I say huh?" - Buffy Re: WM_PRINT for themed controls Heath Stewart29-Jul-04 9:25 Heath Stewart 29-Jul-04 9:25  First, don't handle the WM_PAINT message. Override OnPaint for your controls (unless you're using an IMessageFilter or something) and use Control.SetStyle with the ControlStyles enumeration (read the .NET Framework SDK documentation for details) to control exactly what gets drawn. If you don't want this code to run on Windows XP, use the Environment.Version property to determine on what platform and version of the OS the environment (the CLR) is running. Use that as a condition to executing certain code.   Microsoft MVP, Visual C# My Articles Calculating Point locations in relation to Parent client area. Tristan Rhodes29-Jul-04 6:27 Tristan Rhodes 29-Jul-04 6:27  I have a number of controls that are interacted with using mouse events. These work fine until the area they are in is scrollable, then, because they are tied to the screen location rather than the parent client area location, they don't function properly. How would I calculate the location in relation to the parent instead? Seems like a simple thing, but i'm mildly confused by it. Regards Cata Re: Calculating Point locations in relation to Parent client area. Nick Parker29-Jul-04 8:06 Nick Parker 29-Jul-04 8:06  Look at the Control.PointToClient[^] method. - Nick Parker My Blog | My Articles Re: Calculating Point locations in relation to Parent client area. Anonymous30-Jul-04 13:42 Anonymous 30-Jul-04 13:42  Thanks Nick, but that didn't solve the problem. I tried point to client using the parent panel calling the method using the screen point taken from the control. This works the same as before however. The problem I have is with scrolling. The client area remains the same, even if the client area has been scrolled down or across. This means that the information I am getting is still out of sync with the display. I can't find a way to get the X and Y values of the scrollable client. I.e. if i scroll halfway down both X + Y axis, it still tells me I'm clicking on coordinates {300, 375}, when it should say i'm on {5300,5375}. Any other ideas? Cata CheckedListBox event handling strangeness James Kolpack29-Jul-04 5:32 James Kolpack 29-Jul-04 5:32  Hi, I want to update both the contents and the checked state of items in a CheckedListBox on the ItemCheck event. It turns out that when removing an item that occurs before the checked item (the one that is being processed), both this checked item and the one after it will appear to be checked after the event finishes. To illustrate, here is some code that first populates a CheckedListBox with a sequence of integers (named checkedListBox), and then when an item is checked, removes this item, and also checks the previous item if it was even, or the following item if it was odd. private void checkedListBox_ItemCheck(object sender, System.Windows.Forms.ItemCheckEventArgs e) { // get the currently checked index int checkedItemIndex = (int)checkedListBox.Items[checkedListBox.SelectedIndex]; bool checkedEven = checkedItemIndex % 2 == 0 ? true : false; // remove the event handler for now - it is triggered by SetItemCheckState checkedListBox.ItemCheck -= new ItemCheckEventHandler(checkedListBox_ItemCheck); // if it was an even number, check the previous index // ie - checking 4 will result in 3 being checked // else, check the following index // ie - checking 5 will result in 6 being checked if (checkedItemIndex > 1 && checkedEven) checkedListBox.SetItemCheckState(checkedItemIndex - 1, CheckState.Checked); else if (checkedItemIndex < checkedListBox.Items.Count - 1) checkedListBox.SetItemCheckState(checkedItemIndex, CheckState.Checked); checkedListBox.ItemCheck += new ItemCheckEventHandler(checkedListBox_ItemCheck); // remove the currently clicked index checkedListBox.Items.RemoveAt(checkedItemIndex); } // here is the code to populate the box private void resetListBoxContents() { checkedListBox.Items.Clear(); for (int i=0; i < 20; i++) checkedListBox.Items.Add(i); } As you see, when checking 9, 9 is removed and 10 is checked. But when 4 is checked and removed, 3 becomes checked, as it should be, but so is 5, which should not be. Any help in this matter would be greatly appreciated. Thanks! Re: CheckedListBox event handling strangeness Nick Parker29-Jul-04 8:01 Nick Parker 29-Jul-04 8:01  Just a question, what is the purpose of having the check box if the item disappears as soon as you click on it? - Nick Parker My Blog | My Articles Re: CheckedListBox event handling strangeness James Kolpack29-Jul-04 8:31 James Kolpack 29-Jul-04 8:31  In actual use, probably none - I've only used to illustrate the problem I've been having. In the real implemenation, I'm removing entries from the box which are mutually exclusive with the checked item. The problem seems to be that the check gets set after the event has finished, and instead of applying it to the clicked item (which may have moved in this case), it checks the index of where that item originally was. Does this make sense? Perhaps there is another control I can use to facilatate this behavior? Re: CheckedListBox event handling strangeness James Kolpack29-Jul-04 11:12 James Kolpack 29-Jul-04 11:12  Found the solution - when editing the state of the currently checked item, do so through the ItemCheckEventArgs parameter. Easy fix. C# DataGrid - how to get the sort arrow in column header T J Manjaly29-Jul-04 5:03 T J Manjaly 29-Jul-04 5:03  I am writing a custom grid, inherited from datagrid. I use data-binding to populate grid from an ArrayList. When I click the column header, I am capturing the click and sorting the arraylist and re assign the data source to populate grid with sorted data. My problem is, I do not get the sort arrow in the column header. How can get this? Thanks in advance. - TOJO Column selection control needed Jan R Hansen29-Jul-04 4:38 Jan R Hansen 29-Jul-04 4:38  Hi everybody, I need a control that allows the user to select between n columns to show in a grid / listview. Much like the ones seen in e.g. Outlook where you have a list of available columns in a left hand list and a right hand list with the ones you have selected. In between there is buttons used to move "columns" from one window to the other, one at the time or all of them. I've searched the net, looked through the C# controls list here on CP - but with no luck. Does anybody know of such a control, or is this a candidate for my first CP article ? Thanks in advance - have a nice day ! /Jan Do you know why it's important to make fast decisions? Because you give yourself more time to correct your mistakes, when you find out that you made the wrong one. Chris Meech on deciding whether to go to his daughters graduation or a Neil Young concert

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