difference b/w readonly and const? - C# Discussion Boards

Re: "Insert into" with c#

eugene.genis25-Jan-07 2:01

eugene.genis

25-Jan-07 2:01

Butterfly_h wrote:
("INSERT INTO Accessories (accessory-type, accessory-price)" + "VALUES('" + x + "','" + y + "')",

try using the escape char with your single quotes... for example "VALUES(\'" + x + "\', \'" + y + \'")

are x, y and the relevant db columns of the same data type?

Re: "Insert into" with c#

Butterfly_h25-Jan-07 2:41

Butterfly_h

25-Jan-07 2:41

yes they are.
If you can go through the code I have three tables each has the same insert statement but it only works with the Material table.

I'll try your suggestion and tell you what happens.

Regards,
Butterfly

Re: "Insert into" with c#

Luc Pattyn25-Jan-07 2:58

Luc Pattyn

25-Jan-07 2:58

I once more suggest you list the three actual INSERT lines (on 3 consecutive lines!),
and I am confident you will spot the problem.

Smile | :)

Luc Pattyn

Re: "Insert into" with c#

Butterfly_h25-Jan-07 14:56

Butterfly_h

25-Jan-07 14:56

I tried it and it still not working!
Please if anyone figures it out to tell me.

Regards,
Butterfly

Re: C#: Syntax error in INSERT INTO statement

Butterfly_h29-Jan-07 6:40

Butterfly_h

29-Jan-07 6:40

Hello again,
I got the solution to my error and it was in the columns names in both Material and Accessories tables.
I should have used [,] with the column names containing -.

Thanks for your responses.

Regards,
Butterfly

how to set password on exe file ?

hdv21224-Jan-07 11:17

hdv212

24-Jan-07 11:17

hi i want to set password on my exe file,i know that i run this operate via Executable header but i don't found an article that use executable header in c#.
anybody can help me >?
thanks

Re: how to set password on exe file ?

Ed.Poore24-Jan-07 12:34

Ed.Poore

24-Jan-07 12:34

Eh?

Can you explain more clearly.

Do you want to ask the user for a password when they run the program?
If so then just add a password dialog before anything else in your main routine.

Or are you trying to encrypt the contents of the executable?

I have no idea what I just said. But my intentions were sincere.

Poore Design

difference b/w readonly and const?

Rahithi24-Jan-07 10:46

Rahithi

24-Jan-07 10:46

hi,
please can anyone tell me the main difference b/w Read-only variable & Constant variable??

thanks,
Rahi

If you look at what you do not have in life, you don't have anything,
If you look at what you have in life, you have everything... "

Re: difference b/w readonly and const?

Stefan Troschuetz24-Jan-07 10:56

Stefan Troschuetz

24-Jan-07 10:56

Citing MSDN: "The readonly keyword is different from the const keyword. A const field can only be initialized at the declaration of the field. A readonly field can be initialized either at the declaration or in a constructor. Therefore, readonly fields can have different values depending on the constructor used. Also, while a const field is a compile-time constant, the readonly field can be used for runtime constants" (readonly (C# Reference)[^])

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning." - Rick Cook

www.troschuetz.de

Re: difference b/w readonly and const?

Christian Graus24-Jan-07 11:02

Christian Graus

24-Jan-07 11:02

readonly is evaluated at runtime, const is evaluated at compile time. So, if you use a const value from one dll in another, you need to redistribute both dlls if the value changes. If it's read only, you need only replace the dll that changes the value.

Christian Graus - C++ MVP

'Why don't we jump on a fad that hasn't already been widely discredited ?' - Dilbert

Re: difference b/w readonly and const?

Josh Smith24-Jan-07 11:06

Josh Smith

24-Jan-07 11:06

Also, you can have a const value type, but not a const reference type (except for System.String). Readonly can be either value or reference type objects.

:josh:
My WPF Blog[^]

We are what we repeatedly do. Excellence then, is not an act, but a habit. - Aristotle

Re: difference b/w readonly and const?

Marcelo Calado24-Jan-07 11:31

Marcelo Calado

24-Jan-07 11:31

This link could help you:

http://blogs.msdn.com/csharpfaq/archive/2004/12/03/274791.aspx[^]

Do you need develop a Professional Software with low cost? Contact me!

Re: difference b/w readonly and const?

Rahithi24-Jan-07 14:05

Rahithi

24-Jan-07 14:05

Thanks to all who answered my question. now i came to know what is the difference b/w read-only & a constant.

Thanks,
Rahi

If you look at what you do not have in life, you don't have anything,
If you look at what you have in life, you have everything... "

C# PictureBox.MouseDown

kselman24-Jan-07 10:25

kselman

24-Jan-07 10:25

I hope this is an easy one. It seems like it should be.

I have a pictureBox that I am using as a button. I'm swapping images in and out for up and down states. When the user clicks and holds the mouse down I want it to execute the MouseDown code multiple times until they MouseUp.

<br />
private void mirrorAdjust_MouseDown(object sender, MouseEventArgs e)<br />
{<br />
    mirrorPictureBox.Image = Resources.MirrorDown;<br />
    <br />
    //while(MouseDown) ?? Is there a state I can check here?<br />
    FunctionToRepeatUntilMouseUp();<br />
}<br />
<br />
private void mirrorAdjust_MouseUp(object sender, MouseEventArgs e)<br />
{<br />
    mirrorPictureBox.Image = Resources.MirrorUp;<br />
}<br />

Re: C# PictureBox.MouseDown

Martin#24-Jan-07 10:31

Martin#

24-Jan-07 10:31

Hello,

In this case you have to work with a timer. (System.Windows.Forms.Timer for example)

You set the Enable Property true at Mouse Down.
In the tick event code you than add the mousedown code.
At mouse up you have to set Enable to false. (Also at MouseLeave to be sure)

Hope that helps,

All the best

Martin

Re: C# PictureBox.MouseDown

kselman24-Jan-07 11:29

kselman

24-Jan-07 11:29

Thanks for the quick reply!

Sounds good I will use a Timer then..

Thanks
-Kevin

Re: C# PictureBox.MouseDown

Luc Pattyn24-Jan-07 15:20

Luc Pattyn

24-Jan-07 15:20

I have not done this, but I expect you can use a regular Button, give it no text,
but add a picturebox to its Controls property, hence combining the best of both.

Smile | :)

Luc Pattyn

Question about form designer

reutre24-Jan-07 10:19

reutre

24-Jan-07 10:19

I'm writing a form based app using the tab control. I want to make the app as modular as possible so it will be easy to modify and extend.

My intention is to subclass TabPage and design each tab separately so it can be "plugged in" to the main app (at compile time, not run time). Ideally, my subclassed TabPage would be usable in the form designer to lay out the controls for that tab.

In practice, however, I'm finding that form designer will not display my subclassed TabPage in design view, it will only show me the controls present on the page as icon view. My question is this: Is there any way to make my subclassed TabPage show up in form designer the way I want?

Thanks,

Trent R

Re: Question about form designer

Ed.Poore24-Jan-07 12:40

Ed.Poore

24-Jan-07 12:40

One solution would be to use a UserControl / Panel which would allow you to lay out the controls as you want.

You could then either load this custom control onto a tab page, or you could simply change the inherited class from UserControl to TabPage, hopefully the layout logic that was generated by the designer will remain there (it might disappear though if you try and re-load it into the designer).

The safest would probably be to use a UserControl as the "subclassed" TabPage and then simply drop this onto an existing tab page.

I have no idea what I just said. But my intentions were sincere.

Poore Design

SelectionStart error on custom TextBox...

Lord Kixdemp24-Jan-07 10:04

Lord Kixdemp

24-Jan-07 10:04

Hello everyone! Big Grin | :-D

I'm trying to make a custom text box for currencies... It instantiates this control:

http://www.codeproject.com/useritems/FilterTextBox.asp

I never made a custom control before, so these are my exact steps: :P

1. Go to Project->New
2. Select 'Windows Control Library' and click OK
3. Add a reference to FilterTextBox.
4. Change UserControl to FilterTextBox on both partial classes.
5. It gave me an error on compile, so I had to remove the second line inside InitializeComponent() on file UserControl1.Designer.cs:
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
6. I typed in my custom code:

public CurrencyTextBox()
		{
			// Digits only
			MustContain = ".0123456789";
			InitializeComponent();
		}

		void OnEnter(EventArgs e)
		{
			base.OnEnter(e);

			double a = Convert.ToDouble(Text);
			this.BackColor = Color.Aqua;

			Text = a.ToString();
		}

7. I add the DLL to my program's References and to the Toolbox, but when I try and drag it to my form I get this message:

InvalidArgument=Value of '-1' is not valid for 'SelectionStart'.<br />
Parameter name: SelectionStart

Hmm... I got this message a bit ago as an exception when using a FilterTextBox, in my Leave event handler for that control... Maybe there's a problem with me making my own OnEnter? Help! Thanks! Wink | ;)

Windows Calculator told me I will die at 28. Frown | :(

Re: SelectionStart error on custom TextBox...

Martin#24-Jan-07 10:20

Martin#

24-Jan-07 10:20

Hello,

I think the error you made, is choosing this FilterTextBox!
There are much better articles here on CP.

After a quick search I found code like:

this.SelectionStart = p-1;

Without any validation before.

So really I think the error comes from the Control youre usercontrols inherit from.

P.S.: You should use double.TryParse instead of Convert.ToDouble.

All the best,

Martin

Re: SelectionStart error on custom TextBox...

Lord Kixdemp24-Jan-07 11:58

Lord Kixdemp

24-Jan-07 11:58

Hmm... yeah, there are a few... Which do you recommend? I don't wanna choose a bad one again... Thanks! Wink | ;)

Windows Calculator told me I will die at 28. Frown | :(

Re: SelectionStart error on custom TextBox...

Martin#24-Jan-07 19:42

Martin#

24-Jan-07 19:42

Hello,

http://www.codeproject.com/info/search.asp?cats=3&searchkw=Numeric+TextBox&Submit1=Search&author=&sd=15+Nov+1999&ed=25+Jan+2007[^]

The first and second looks good.

All the best,

Martin

Re: SelectionStart error on custom TextBox...

Lord Kixdemp27-Jan-07 16:41

Lord Kixdemp

27-Jan-07 16:41

OK, I'll try 'em! Thanks! Wink | ;)

Windows Calculator told me I will die at 28. Frown | :(

Checking if a handler is sbuscribed to an event

Dan Neely24-Jan-07 9:42

Dan Neely

24-Jan-07 9:42

Can I check if a given handler is assigned to an event.

I'm having problems with events I want to fire in most cases, but not under a few specific instances. I'm currently using InstallFooHandlers() and RemoveFooHandlers() to control the firing, but the system breaks down in one case where methods Bar() and Baz() both need the handlers disabled, but Bar() calls Baz() internally, because at their conclusion's both methods install the handlers resulting in two copies being attached to each event and the next pass through not removing them. Putting a pair of install/remove calls around Bar()'s call of Baz() would work but I'd prefer something less kludgey if possible.

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