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Hi ...
I'm having trouble setting the values of the array in my class.
I tried this ... and i can set/get "x.name" but pgm crashes with an error message that says i do not have an instance of the array item when i try to set "x.number[1]".
namespace WindowsApplication1
{
public partial class Form1 : Form
{
class myClass
{
// fields
private string _name;
private double[] _number;
// properties
public string name
{
get { return _name; }
set { _name = value; }
}
public double[] number;
public double this[int index]
{
get { return _number[index]; }
set { _number[index] = value; }
}
// Default constructor:
public myClass()
{
name = "";
double[] number = new double[5];
number[0] = 0;
number[1] = 0;
number[2] = 0;
number[3] = 0;
number[4] = 0;
}
// Clear Numbers
public void ClearNumbers()
{
double[] number = new double[5];
number[0] = 0;
number[1] = 0;
number[2] = 0;
number[3] = 0;
number[4] = 0;
}
}
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
myClass x = new myClass();
x.name = "Charlie";
x.number[1] = 123.45;
}
}
}
My program works on x.name = "Charlie";
My program fails on x.number[1] = 123.45;
Please advise on how to fix my class definition to accomodate arrays.
Thank you.
-- modified at 10:17 Saturday 25th March, 2006
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The code in the constructor is not even possible to compile. Why don't you show the code that you really are using?
I assume that the code in the constructor looks like the code in the ClearNumbers method, as that at least compiles...
You have two array references in the class, _number and number. You never assign anything to any of them, so of course you get an error message when you try to use any of them. If you look at the task list after compiling, you will see that the compiler has given you very informative warnings about this.
---
b { font-weight: normal; }
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Sorry ... i have corrected the original post.
i should have just copy/pasted the whole original .. i did not actually save that much space when i copied just part of the problem ... and i introduced an error.
Thank you for pointing that out.
As you can tell ... i am a newbie at class definitions. I have no idea why the underscore character precedes the field names and then (if needed at all) why it is not used in EVERY reference to the field.
But not having a knowledgeable mentor ... i am subject to the problems associated with "mimicking" what i have seen in other class definitions.
I think u get the idea of what i am trying to accomplsh. Please suggest code change to the class so the button code works.
Thanks.
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You have two arrays, like Guffa said, number and _number and you dont assign anything to either of them. The fact that they have the same name, give or take an underscore, means nothing, they are completely different variables that are in no way related to each other.
Your code crashes on x.number[1] because you havent initialised number to anything, and so it is currently null. So trying to access the second value of it will crash because there is no second element. Try the following code, is should work...
class myClass
{
private string _name;
private double[] _number = new double[5];
public string name
{
get { return _name; }
set { _name = value; }
}
public double[] number
{
get { return _number; }
set { _number = value; }
}
public double this[int index]
{
get { return _number[index]; }
set { _number[index] = value; }
}
public myClass()
{
name = "";
_number[0] = 0;
_number[1] = 0;
_number[2] = 0;
_number[3] = 0;
_number[4] = 0;
}
public void ClearNumbers()
{
_number[0] = 0;
_number[1] = 0;
_number[2] = 0;
_number[3] = 0;
_number[4] = 0;
}
}Hope that helps 
Cheers,
Will H
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Thank you so VERY much, Will ! Your suggestions work great!
I still do not understand the use of "this" in the code block ...
public double this[int index]
{
get { return _number[index]; }
set { _number[index] = value; }
}
... but for the time being, until i get that understanding, i can mimic what u showed me for future class definitions.
Your help is much appreciated!
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That code block is there so that you can access myClass as though it was an array itself. It means that if you create an instance of myClass like so
myClass foo = new myClass(); then you can access your _number array in two ways. Like this...
double firstElement = foo.number[0]; and also like this...
double firstElement = foo[0]; The last way is only allowed because of the 'public double this[int index]' accessor.
Glad I could help
Cheers,
Will H
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Hey guys, is it possible to Dial a Number Using C# and be able to speak with the other person, using C#.
I'm writting a PhoneBook application i want to be a ble to search a number an dbe able to dial it.
By the way i want to have a help for my project, I haven't done such thing before, what's the best way fo doing so ?
I'd be grateful
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How could i select a single speaker to play a sound with DirectSound?
I've a 5.1 soundcard which is configured as sorround sound, so that i can use the 6 outputs. This card appears in the system as one device (i have another 5.1 card and, with special drivers, it appears as 3 stereo devices, so it s easier to use, but i cannot use these drivers on the first card) and ive seen an application which can play a sound to a single speaker, so i should be able to do it too.
Ive thought about playing the sound as a 3D sound and selecting its position, but i dont think it s a good idea.
Any idea? Thx
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hello all in codeproject,
i am new to the programming field and i would like to know more about how to use constructors and why do we use them regarding the idea that we can initialize our variables in any section without using constructors.
thank you for your concern
abdelhameed81@yahoo.com
abdelhameed
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abdelhameed81 wrote: how to use constructors
See the program class to see how to use constructors
public class A
{
private string myText;
public A(string someText)
{
this.myText = someText;
}
public void WriteMyText()
{
Console.WriteLine(someText);
}
}
public class Program
{
public static void Main()
{
A a = new A("Hello World");
a.WriteMyText();
}
}
abdelhameed81 wrote: why do we use them regarding the idea that we can initialize our variables in any section without using constructors.
Because it is good practice to initialise the fields to something sensible. The CLR will initialise the fields to default values if you don't set them. e.g. an int will be set to 0, a string to "" and so on. But they may not be sensible for your application.
In objects that are immutable there is no opportunity to set the fields after the constructor has setup the object. The very nature of an immutable object is that it does not change. So it MUST set the class fields at construction. For example the string class is immutable, you cannot change a string object, you can only create new string objects.
Sometimes you may have a situation where a field is a lazy lookup because it isn't used often and it takes a long time to retrieve the value. In that case it would be initialised to null (if it is a reference type) and the getter property would do the lookup and cache the value in the field when it has been retrieved.
ColinMackay.net
Scottish Developers are looking for speakers for user group sessions over the next few months. Do you want to know more?
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Colin Angus Mackay wrote: The CLR will initialise the fields to default values if you don't set them. e.g. an int will be set to 0, a string to "" and so on.
A slight correction, just to avoid misunderstandings:
A string will be initialised to null, not to an empty string.
---
b { font-weight: normal; }
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A construtor is always used to create an object. If you don't declare a constructor for a class, an empty constructor is created.
As there always is a constructor, it's a sensible place to initialize the data in the object. That way it's impossible to forget to initialize it.
---
b { font-weight: normal; }
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hi,
i am using TAPI3 for outgoing call, i make call but the problem is how do i know whether otherend has picked up the phone or not because when phone is picked up by someone i want to play audio.
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I'm trying to do the same thing from the scartch can you give me a sample code or something like that to call a number in a C# from ...
Thanks
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I also want to do it. Please guide me or give some code for demonstration purposes. I'll be so thankful to you.
Best Regards,
Rizwan
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i am in a project containing a part that give someone a call
will you give me a sample code too in C#
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I don't hav such code ...
what language are you using ?
Mr.K
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Hi,
Can We detect Sql Servers on Network using c#
Like when we reister new conection sql server it shows the list of all server in the network.
This is same i need to do in my c# product installer.
Thanx & Regards
Anuj Kamthan
Software Developer
Solversa Technologies,
Pune - 411007, India.
http://www.solversa.com
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Hi, I am trying to develop an ActiveX control in C# that changes the text of the textboxes on the client machine...for this purpose...i got the code, that closes a window using the window name and the class name in a WINDOWS FORM.
class Win32{
public const int WM_SYSCOMMAND = 0x0112;
public const int SC_CLOSE = 0xF060;
[DllImport("user32.dll")]
public static extern int FindWindow(
string lpClassName, // class name
string lpWindowName // window name
);
[DllImport("user32.dll")]
public static extern int SendMessage(
int hWnd, // handle to destination window
uint Msg, // message
int wParam, // first message parameter
int lParam // second message parameter
);
}
// Determine the handle to the Calculator window.
int i=Win32.FindWindow(txtClsNm.Text ,txtWndNm.Text);
// Post a message to Calc to end its existence.
int j=Win32.SendMessage(i, Win32.WM_SYSCOMMAND, Win32.SC_CLOSE, 0);
However, when i tried to use the same in an activex control, it gave me a security exception...
************** Exception Text **************
System.Security.SecurityException: System.Security.Permissions.SecurityPermission
at ActiveXDotNet.myControl.button2_Click(Object sender, EventArgs e)
at System.Windows.Forms.Control.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnClick(EventArgs e)
at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ButtonBase.WndProc(Message& m)
at System.Windows.Forms.Button.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
The type of the first permission that failed was:
System.Security.Permissions.SecurityPermission
The Zone of the assembly that failed was:
MyComputer
Can anyone tell me how to solve this problem...ideally tell me the API call that helps me CHANGE the text box contents at the client machine...
just in case ,it helps, to develop an activex control in .NET, i created a "Class Library" project and put a "User control" over it...
PLEASE help!! 
thanx
Wajih
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Hello
How can i create class libraries that can be used only in my program.
Thanking You
Navaneeth
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I don't think there is any mechanism which prohibits other programs to use your class library.
As a thought, what can be done is have a sort of login functionality in your class library. I mean, before anyone can use any of the functions in your class library, they have to first login to your class library. Create a function known as login, which takes a username and a password. If the username and the password are correct, set an internal flag to true. Now when other functions are being called, check for the internal flag! If the internal flag is false, don't execute the function, if it is true then go ahead as it normally would.
bool blnValidUser = false ;<br />
<br />
bool LoginUser( string strUserName, string Password )<br />
{<br />
if( username and password match )<br />
{<br />
blnValidUser = true ;<br />
return true ;<br />
}<br />
else<br />
{<br />
blnValidUser = false ;<br />
return false ;<br />
}<br />
}<br />
<br />
void function1()<br />
{<br />
if( blnValidUser is true )<br />
{<br />
Go ahead as planned.<br />
}<br />
else<br />
{<br />
return ;<br />
}<br />
}
Hope this helps! 
---
With best regards,
A Manchester United Fan
The Genius of a true fool is that he can mess up a foolproof plan!
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Hi Experts
I am developing a security system for my software. One copy of product has to be installed only on one pc. So i tried to create a unique system key according to processor id or MAC address. But this is not common, some processors may not have serial no's and more over this will not work with XP and 2000. So anyone suggest a nice tip for providing security and preventing piracy ?
Cheers
 Navaneeth
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Even giants like MicroSoft haven't been successful in curbing piracy. 
Why don't you try a commercial licensing product like Software Shield[^]? One of my clients has used it and they say its great.
All the best!
---
With best regards,
A Manchester United Fan
The Genius of a true fool is that he can mess up a foolproof plan!
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How can I get the bits that compose a byte?
Say I pass a byte of value 10 to my byteToBitArray function, I would
LIKE to get back an array (8 long) of 00001010.
I want that back cause that's the binary representation of the byte 10.
Any idea how to do this?
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Hi,
here a small sample how to build a string representation:
private string Convert(byte b)
{
int curVal = 256;
string temp = "";
while (curVal > 1)
{
curVal /= 2;
if (b >= curVal)
{
temp += "1";
b -= (byte)curVal;
}
else
temp += "0";
}
return temp;
}
It could easely be modified to return a bool array or whatever you need exactly.
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