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Hi All:
I have the following algebraic equations I want to code in C#. I am not sure how to do this. Please help!
495 = 66t + c
951 = 190 + c
How do I write this in code?
Thanks,
Laura
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Sorry the equations are actually:
495 = 66t + c
951 = 190t + c
Thanks! Please Help! 
Laura
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Are you looking for an algorithm for solving two simultaneous equations[^]? And you want to code that in C#?
Make sure you understand the algorithm first without being concerned about how to implement it in C#. Once you have a strong handle on the algorithm, you can then begin to consider how to implement it in C#. The above link describes three approaches.
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You must use the matrix.
for ex:
2x+6y=8
3x+2y=5
|8 6|
|5 2| -14
x=-----= --- = 1
|2 6| -14
|3 2|
|2 8|
|3 5| -14
y=-----= --- = 1
|2 6| -14
|3 2|
sol x=1 y=1.
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this method works for n Equations n Unknows.
FOR 2 Equations 2 Unknows
For one system like this:
{a*X+b*Y=c
{d*X+e*Y=f
the part of code ar:
if (a*e-d*b)
{
X=(c*e-f*b)/(a*e-d*b);
Y=(a*f-d*c)/(a*e-d*b);
}
else
{
MessageBox.Show("Many solution!!!");
}
PS:
The determinant
|a b| is equal with a*d-b*c
|c d|
math my love
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Hi,
If I set up a http server on a pc in a LAN with NAT firewall
(the ip of the http server obtained by checking the "IPConfig" of the pc), then can other pcs outside the LAN access my http server with the ip ?
If not, how can the MSN Messenger and other IM access throught the NAT firewall ?
Thanks
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Hi
Well that doesn't sound like a c# question... 
anyway.. there are possibilities to do this.
1. you can configure a port-relay on the firewall (all connections to the router on a specific port are relayed to a specific lan-address)
2. if you have more than one address and you have an firewall with that fuction you can also configure an address - relay (all connections to one of your external addresses are relayed to a specific lan-address)
i think reading the manual could help you on this for more details 
msn messenger an other IM work different. i'm not 100% sure about it but i guess they work like this:
if you want to send a file from one IM to another they
1. try to connect from the sender to the receiver
2. if 1 didn't work try to connect from receiver to sender
3. if 2 didn't work send the file via IM server
greets
m@u
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I have a pocket PC which I would like to request data from a xml file on a website and loop thru all the nodes. So I have the basic testing application, but I have two problems.
When I am in the emulator state and I try and request a URL of a very simple file which the contents of the html are only "blank file" then during runtime I get a error that says...
WebException was unhandled
This code is the exact same code I use on a desktop application, does anyone know why the below code would report this error?
string xmlLoadFrom = "https://www.domainhere.com/test.php";<br />
string strResponse = "";<br />
WebRequest req = WebRequest.Create(xmlLoadFrom);<br />
req.Timeout = 1800000;
WebResponse resp = req.GetResponse();<br />
StreamReader sr2 = new System.IO.StreamReader(resp.GetResponseStream());<br />
strResponse = sr2.ReadToEnd().Trim();<br />
sr2.Close();<br />
resp.Close();<br />
<br />
MessageBox.Show(strResponse);
The error occurs on this line
StreamReader sr2 = new System.IO.StreamReader(resp.GetResponseStream());
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Hi,
Wasn't sure exactly what forum to post this to, but in case this could be a problem in my code (C#), I decided to post it here.
Having a very strange problem here. Have a custom control. Inherited from ListView. I call it ImageView. Have a custom property on it called Thumbnail which itself is actually an object with multiple properties. Using a custom TypeConverter which inherits from ExpandableObjectConverter. Have a form with the ImageView on it. I open Visual Studio and open the form without making any changes to my project or compiling. The string to object (and vice versa) conversion for the Thumbnail property works exactly as it should in the property grid for the ImageView. I make a change...ANY change...to my project and recompile, it breaks. After recompiling, I open the form and in the textbox to the right of the Thumbnail property name in the property grid reads the full namespace.class.class string instead of the custom text which represents the property settings. I modify the text, but even if I change to something that should convert to the object, it gives me cannot convert to System.String errors, object not instantiated errors, and casting errors (not all at once, but I've gotten at least one of each of these errors throughout my troubleshooting). Without making any changes, I close out of VS (just closing the form or closing the project doesn't do it, I must close completely out of VS), and then open VS again, open the form without making any changes or compiling, it works. As soon as I make a change anywhere (even just adding a file to the project) and then compile, it breaks. I'm using VS Standard Edition w/ SP1. It was doing this before SP1 and continues to do so afterwards. I've tried repairing VS, even uninstalling and reinstalling, to no avail. I've tried creating new projects and creating quick small objects and converters and adding them to an inherited control within the new project. Happens then, too. Oddly enough, though, it seems this started happening when I made a class name change with one of the other expandable properties I already had on the ImageView. It seems lots of things went haywire when I did that. Got everything worked out except this. Since then, I haven't been able to kill this bug. Have any of you experienced this? Could this be a bug in VS, or could there be something strange with my code that would be causing this?
Sorry for the long-winded post. Strange and complex issue. Wanted to get all the details in.
Thanks
Rob
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Hi..
If you put the your ImageListView into a DLL Project and refer to it from your EXE Project you won't have the problem anymore.
greets
m@u
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Well...you are correct. I did exactly that and problem solved. Now my next question. Why? What's different about referencing the dll into the project that makes that work right?
Rob
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Nevermind...still have same problem. Except this time, when I make a change in the DLL project, compile it, then go to the EXE project and pull the changed reference in, compile, the same thing is happening in the property grid as described above as soon as I open the form with the ImageView on it. If I then close out of VS, relaunch VS, and go directly into the EXE project, open the form, it's fine. Close EXE project, open DLL project, make ANY change, compile, close DLL project, open EXE project, pull in new reference, compile, open form, broken. Immediately close VS, relaunch VS, open EXE project, open form, it's fine. There is still definitely a problem here.
Rob
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Finally got the solution. Override the ToString() method of the expandable objects and return String.Empty, or whatever string you wish, I suppose. Apparently when the control is constructed in the designer, each expandable object automatically spits out its ToString() results to the box next to the property name in the property grid resulting in the full type name of the object unless otherwise specified in an overridden ToString() method. My custom ObjectConverters also seem to still work as well.
Rob
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Well...that didn't quite do it. That does away with the full type name appearing there, but the object converters are still broken when I make a change in the dll project, compile, re-open the exe project, open the form with the ImageView on it, and view the property grid for the ImageView. I still have to close out of VS and re-open it for it to not be broken. When it's broken, I get the following error when I type the correct text next to the property name and hit Enter.
Object of type 'WallpaperQuickSelector.Filter' cannot be converted to type 'WallpaperQuickSelector.Filter'.
This is for the Filter object on the ImageView. I get the same for the Thumbnail object for its type:
Object of type 'WallpaperQuickSelector.Thumbnail' cannot be converted to type 'WallpaperQuickSelector.Thumbnail'.
Rob
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I want to access VS's Main Window Context Menu (is that a MWCM, lol). Where in the document model can I add and remove a item to the Cotext Menu?
You can only be young once. But you can always be immature.
- Dave Barry
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Hello,
[VS 2005]
I am using typed datasets. I have 2 datagridView and when I click one GridA it will add a row to GridB. This works fine and the data is saved to the database.
However, the customer wants to add the rows to GridB and save periodically.
I am wondering is there a way to show the rows that have not been saved, and when the user clicks the save button it will change them to a different colour.
So it will commit some rows everytime the user clicks save. The user can add some more rows and they will be displayed in blue. Once the user clicks save all the rows that have just been added will be saved to the database and then change colour to green.
Can anyone point me in the right direction or give me some code example, will be most grateful.
Many thanks,
Steve
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A DataGridViewRow has the DefaultCellStyle Property, which is of the type DataGridViewCellStyle and has the BackColor property.
you can just give it any color you want. It's probably better to add a (hidden) saved/notsaved column to your datagrid or it's source, then only relying on the color. Then you can ovverride the datagrid.Paint method to display the colors.
Visual Studio can't evaluate this, can you?
public object moo<br />
{<br />
__get { return moo; }<br />
__set { moo = value; }<br />
}
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Hi all,
I want to do the following:
Provide an App Server that, amongst other things, creates a set of dyamically generated classes.
Allow a client app (that I develop) to connect to the App Server and retrieve, via a Remoting call, the server's dynamically created Assembly so that the client app can use the classes that the server Dynamically created (via Relection of course).
I've completed the dynamic code generation of a working set of classes within an 'in memory' dynamically compiled Assembly. What I need to know is how to 'serialise' the assembly back to the client in a manner that allows the client to use the classes in that assembly.
The 'Assembly' class is Serializable, so I've tried providing the obvious server side remoting method:
// In the server:
public class ServerClass : MarshalByRefObject
{
public Assembly GetDynamicAssembly()
{
// Return the assembly containing all my dynamically created classes).
return myDynamicallyGeneratedAssembly;
}
}
// In the client:
ServerClass RemoteServerClass = (create Remoted Server Reference);
Assembly dynamicAssembly = RemoteServerClass.GetDynamicAssembly();
The above call to GetDynamicAssembly() fails with an error along the lines of:
"Could not load file or assembly 'd9ee95f9, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified."
The 'd9ee95f9' is obviouly the randomly created assembly name for the dynamic assembly and changes each time I try it.
Is it possible to do what I want, and if so how?
Trevor
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i want to read image of the pictureBox as byte array,how do i this work?
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as a last resort:
Bitmap bmp = new Bitmap(pictureBox1.Image);
byte[] buf = new byte[bmp.Width * bmp.Height * 3];
long i = 0;
for(int y = 0; y < bmp.Height; y++)
for(int x = 0; x < bmp.Width; x++)
{
buf[i++] = bmp.GetPixel(x, y).R;
buf[i++] = bmp.GetPixel(x, y).G;
buf[i++] = bmp.GetPixel(x, y).B;
}
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i have a text box witch bindes to a table,i want to save the changed text in the table,how do i this work with binding method?
(with Acceptchange() )
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I couldn't find a good resouce that gives the introduction on about Provider Model, what is it used for and how can one build. Does anybody have a usual link. I searched but getting more confused seems like its a very detail topic but i want to learn first about the basic idea and then drill down in detail afterwards.
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I am building a chat with file transfer support. I use normally the StreamReader and the StreamWriter built over the NetworkStream, but when i want to send data from a file i would like to use NetworkStream directly, to write bytes without encoding/decoding. If i don't use direcly the NetworkStream (convert all my byte[] to char[], then sending, and converting back after receive) things goes fine.
...
NetworkStream networkStream = socketForServer.GetStream();
StreamReader netStreamreader = new StreamReader(networkStream);
StreamWriter netStreamwriter = new StreamWriter(networkStream);
...
//The writer program:
byte[] buf = ...
netStreamwriter.WriteLine(someString);
netStreamwriter.WriteLine(buf.Length);
netStreamwriter.Flush();
networkStream.Write(buf, 0, buf.Length);
networkStream.Flush();
...
//The reader program:
myString = netStreamreader.ReadLine();
size = Convert.ToInt32(netStreamreader.ReadLine());
byte[] buf = new byte[size];
networkStream.Read(buf, 0, size);
...
This does not work, oh it does for the first times (randomly each run) and then unexpected happens, it cuts parts and reader program reads thrashes because of desincronization with the sending program. Is there another way of sending/receiving raw data ? What am i missing...
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OK, I have a class "Dog" with methods play() and Euthanize(). I have a class Child that must be able to "Play" with "Dog", but not "Euthanize" it. I have a class "Vet" that must be able to "Euthanize" "Dog".
I do not want to isolate "Dog" and "Vet" in their own assembly and make "Euthanize" an internal method of "Dog". I also don't want to nest Dog in Vet.
So, How can I enforce these relationships. I do not trust the child to not play vet and "Euthanize" dog, so it must be IMPOSSIBLE for the Child to call "Euthanize" on "Dog".
I don't know if simply giving the child an IPlayable iterface and the Vet an IEuthanizable interface will be restrictive enough as Child could cast IPlayable to Dog and thereby access its "Euthanize" method.
You used to be able to accomplish this with "Friend" classes in C++. There are no friend classes in C#. Am I forced to either put "Vet" and "Dog" in the same assembly and make Dog.Euthanize internal or to nest "Dog" in "Vet" (which doesn't make sense from an object-oriented standpoint because I want classes "Pound" and "PetStore" to be able to create "Dog" objects without any knowledge of the "Vet" class).
Any ideas?
Thanks!
Ian
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Simple. Euthanize() is not a method of Dog, but is a method of Vet, where you pass in a parameter of type Dog. Actually, a better model is if you pass in a parameter of type IAnimal where Dog implements IAnimal. That way, the Vet can't Euthanize(Child), as much as he/she may want to. 
Dave Kreskowiak
Microsoft MVP - Visual Basic
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