Re: Null error when adding custom control - C# Discussion Boards

8-Jan-04 8:39

Hi. I'm a relative newbie with C#...I have some custom controls that are snarfed code from a co-worker (the only other C# code in our workplace).

I have created a windows control library project, added the code to it, and compiled it to the dll. Now I have gone to the custom controls and added them to the pane by selecting the dll file. But when I try to drag the control on to the form it gives me an error:
An exception occured while trying to create an instance of CTSSExp.Controls.ExplorerControl. The exception was "null" is not a valid value for 'control.'".

CTSSExp.Controls is the namespace the control is in and ExplorerControl is the name of the control.

Any suggestions?

Thanks.

There are only 10 types of people in this world....those that understand binary, and those that do not.

Christian Graus8-Jan-04 8:52

8-Jan-04 8:52

yeah - try to avoid cut and paste coding, it leads to errors. Also, avoid the form designer, that's not programming, and the designer really screws with your aspx HTML, sometimes making it invalid and often making it unreadable.

You should put the custom control into a project and use it from that project in order to eliminate any errors, then try putting it into a dll. That way, you are establishing that it works one step at a time.

Christian

I have drunk the cool-aid and found it wan and bitter. - Chris Maunder

KingTermite8-Jan-04 9:00

8-Jan-04 9:00

You are right about cut/paste coding...but in many work environments, its common practice.

However, I did put it in a sperate project (control library template) which compiles (no errors) to a dll.

I then add it to the form designer (add/remove and select the dll file), but when I try to get it after that (it shows up in custom controls tab on the toolbar) and drag it into the form I get that error I mentioned.

I'm sure its something simple...I'm just new to controls and still do not have a "lot" of experience with Visual Studio.Net and the .Net way of doing things.

There are only 10 types of people in this world....those that understand binary, and those that do not.

Christian Graus8-Jan-04 9:06

8-Jan-04 9:06

KingTermite wrote:
You are right about cut/paste coding...but in many work environments, its common practice.

In workplaces populated by idiots. Seriously, if you know it's bad practice, why do it ? Are you GUARENTEED to work in that place forever ? It's just self preservation to learn to do things the best way you can. If your workplace has components it wants reuses, they should be packaged in a dll to start with, and that project should be the only place the controls are modified, via source control.

KingTermite wrote:
However, I did put it in a sperate project (control library template) which compiles (no errors) to a dll.

So there are no compile time errors. I got that before. What does that have to do with run time ?

KingTermite wrote:
I then add it to the form designer

Like I said, don't. The form designer is the tool of idiots. Create a form, play with the designer, then go back to your HTML and see how much it has been screwed with.

KingTermite wrote:
I'm sure its something simple...I'm just new to controls and still do not have a "lot" of experience with Visual Studio.Net and the .Net way of doing things.

Sure - that's why I suggested a couple of steps whereby you can elimanate some factors, and some bad practices, and figure out what the problem is.

Christian

I have drunk the cool-aid and found it wan and bitter. - Chris Maunder

KingTermite8-Jan-04 9:18

8-Jan-04 9:18

Christian Graus wrote:
In workplaces populated by idiots. Seriously, if you know it's bad practice, why do it ? Are you GUARENTEED to work in that place forever ? It's just self preservation to learn to do things the best way you can. If your workplace has components it wants reuses, they should be packaged in a dll to start with, and that project should be the only place the controls are modified, via source control.

No need to be so one-sided....we are not a workplace run by idiots...in fact we are at SEI level 5. Cut/Paste IS a level of reuse. It's called salvaged reuse. We do package "planned" reuse into a dll or other such libary, but my long term intentions are to modify and likely extend this control once I've got it working in the first place.

Now....what HTML are you talking about? I would skip the form designer if I knew how. I need to know how to put the control in if I'm going to do that. I was trying it from the form designer because I thought that was the proper method.

Thanks for trying to help...any more detailed info would be appreciated.

There are only 10 types of people in this world....those that understand binary, and those that do not.

Kentamanos8-Jan-04 9:19

Kentamanos

8-Jan-04 9:19

I never use the form designer either. I click on the tab at the bottom that says "HTML" and go from there. It does save a lot of headaches in the long run.

I, for one, do not think the problem was that the band was down. I think that the problem may have been that there was a Stonehenge monument on the stage that was in danger of being crushed by a dwarf.

-David St. Hubbins

Christian Graus8-Jan-04 9:29

8-Jan-04 9:29

KingTermite wrote:
Now....what HTML are you talking about?

Any aspx page is has a .aspx file and a .cs file. The cs file is your code behind, the aspx file is your page, containing all your HTML, including the asp: tags that denote controls. When you're in the form designer, at the bottom of the page is a 'html' tab, if you click on it, you can hand edit the files. This is definately the way to go, and you should set up your preferences to always go here instead of the designer, for the reasons I mentioned.

And if it were me, I'd create a new control in a project, then copy and paste the html and C# code into it, then change the namespace of the class to match the project, and try to use the control in a page. Unless it's a server control, that's just a cs file, but I'd do the same with that. Not least is the fact that you could then set break points and step through the constructors, etc. to figure out what is going wrong.

Christian

I have drunk the cool-aid and found it wan and bitter. - Chris Maunder

KingTermite8-Jan-04 9:50

8-Jan-04 9:50

Christian Graus wrote:
Any aspx page is has a .aspx file and a .cs file. The cs file is your code behind, the aspx file is your page, containing all your HTML, including the asp: tags that denote controls. When you're in the form designer, at the bottom of the page is a 'html' tab, if you click on it, you can hand edit the files. This is definately the way to go, and you should set up your preferences to always go here instead of the designer, for the reasons I mentioned.

I'll look into what you guys are talking about. Right now I don't see it...I don't see an HTML tab and there are not aspx file (there are some resx files though...maybe that's it?).

Anyway...I think I figured out my problem. There are two controls that I ported (with the exception of using the form designer, I did it exactly as you described for me to do it, Christian). The control that I kept trying (thinking they were all basic controls) was actually a control that contained another control or two within it...since there was nothing there, it was throwing the null exception.

I tried the other control (name didn't sound right to me for what I wanted), but actually turned out to be the control I wanted and was a basic control thus yielded no errors.

There are only 10 types of people in this world....those that understand binary, and those that do not.

Christian Graus8-Jan-04 9:52

8-Jan-04 9:52

Glad it worked out, I've worked out something too. I'm in the C# forum, not the ASP.NET forum. You therefore are probably working on a GUI app and you have no aspx files, no HTML. Sorry, my bad.

Just out of curiosity, is this app for internal use only ? If not, why are you using C#, does your target audience all have the .NET runtime, or will you only distribute on CD, or do you consider the business lost to people unwilling to download the runtime to be negligible ?

Christian

I have drunk the cool-aid and found it wan and bitter. - Chris Maunder

KingTermite8-Jan-04 10:49

How to use PING utility in my program

8-Jan-04 10:49

Christian Graus wrote:
Glad it worked out, I've worked out something too. I'm in the C# forum, not the ASP.NET forum. You therefore are probably working on a GUI app and you have no aspx files, no HTML. Sorry, my bad.

Yes, its a C# app....I guess that is why no aspx files. Smile | :)

Christian Graus wrote:
Just out of curiosity, is this app for internal use only ? If not, why are you using C#, does your target audience all have the .NET runtime, or will you only distribute on CD, or do you consider the business lost to people unwilling to download the runtime to be negligible ?

This will be an internally used app, so distributing the .Net runtime will not be an issue in this case. If the computers don't already have it, the runtime will be included with the install eventually.

Our company does primarily embedded software and test software for host computers to test that embedded software. So we don't have mass produced PC software....so that's never been an issue for us. We sell the entire test sets, computer and all....so if we develop something in .Net, then the software, framework and all will already be on the computer when it is sold to the customer as a "test set".

This allows us to develop, as long as customer has not dictated something special, in whatever environment/language we want (although 90% is currently in C/C++ right now). We have just a few groups that are trying to get a little more cutting edge and trying to bring some new technologies into the arena.

There are only 10 types of people in this world....those that understand binary, and those that do not.

HAHAHA_NEXT8-Jan-04 8:34

HAHAHA_NEXT

8-Jan-04 8:34

How can i use the ping utility in my program.
I need to ping a particular IP address and display the result.

Re: How to use PING utility in my program

Kentamanos8-Jan-04 9:18

Kentamanos

8-Jan-04 9:18

There's two options:

1. Run the ping program by launching it. There's LOTS of examples out there on how to launch a console program and redirect its stdout and stderr back to you.

2. Figure out the ping protocol and write some socket code to do it yourself.

I'm guessing #2 wouldn't be that hard to do, but I've never looked at ping myself.

GDI grab handles and mouse move

Miles Roberts8-Jan-04 7:10

Miles Roberts

8-Jan-04 7:10

Written a GDI package; But now need to:

1.Develop Code which allows shape objects to be dragged (moved) and resized by implementing grab handles. Write a key handler such as when the delete key is pushed the shape dissapears.

Difficult as my shapes arnt saved in array!

2.Add advanced features such as current co-ordinate position of the mouse.

I think this would involve mouse_move and some text boxes

If you can help, i'll send you a zip of my project.

email2miles@yahoo.com

Re: GDI grab handles and mouse move

Heath Stewart8-Jan-04 7:36

Heath Stewart

8-Jan-04 7:36

Miles Roberts wrote:
1.Develop Code which allows shape objects to be dragged (moved) and resized by implementing grab handles. Write a key handler such as when the delete key is pushed the shape dissapears.

In order to do this, each shape will have to be an object so that you can individually manage it. In your MouseDown event, determine if a shape exists under the mouse and begin tracking that shape (perhaps a private field that represents the currently dragging shape). In the handler for MouseMove determine if the mouse is down and if an object is being dragged. If so, shift the coordinates of the object be dragged and call Refresh to invalidate your form and repaint those regions (it would actually be better to invalidate the region previously occupied to the whole form doesn't have to repaint). In your MouseUp handler set he new position of the shape and clear the field that tracks the currently dragging shape.

Miles Roberts wrote:
2.Add advanced features such as current co-ordinate position of the mouse.

Actually, this is pretty easy. The MouseEventHandler passed to you in the handler for the MouseMove event contains the X and Y coordinates of the mouse in the coordinate space of the control that raised the event (such as a Form or Panel onto which you're painting your custom shapes). Just use those and display them in a StatusBar or something:

private void myForm_MouseMove(object sender, MouseEventArgs e)
{
  this.statusBar.Text = string.Format("X={0}, Y={1}", e.X, e.Y);
}

Re: GDI grab handles and mouse move

leppie8-Jan-04 8:13

DO NOT HELP THIS PERSON WITH HIS HOMEWORK!

8-Jan-04 8:13

I suggest if you dont have a plan, that you sit down and make a proper design ASAP. Probably most of the stuff can be stored in a GraphicsPath object.

2. Not advanced, but look at Control.MousePostion

leppie ::AllocCPArticle("Zee blog");
Seen on my Campus BBS: Linux is free...coz no-one wants to pay for it.

leppie8-Jan-04 9:47

Non-rectangular Windows :: the 24-bit issue [advanced]

8-Jan-04 9:47

Received in private email (less attachment nogals):

"The attached file is my working project, if u have any time free, could u implement some grab handles in there? I really havent got time to do this, its due tommorrow.

I think i can get the co-ordinate task done.

Miles"

The answer is NO NO NO, do it yourself. If you cant do it, why the hell are you doing IT in the 1st place. D'Oh! | :doh:

leppie ::AllocCPArticle("Zee blog");
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nibmike8-Jan-04 7:07

nibmike

8-Jan-04 7:07

Dear code gurus,

i'm trying to create a non-rectangular window using a bitmap as background image and setting its transparency key. This works fine, however msdn claims that non-rectangular windows wont work on graphics cards currently displaying more than 24-bit colour, which is true.

My question is, how is MS Media Player doing it anyway if my card is displaying 32-bits?

cheers

Re: Non-rectangular Windows :: the 24-bit issue [advanced]

Heath Stewart8-Jan-04 7:29

Heath Stewart

8-Jan-04 7:29

Windows Layers. See SetLayeredWindowsAttributes in the Platform SDK at http://msdn.microsoft.com/library[^].

Odd. Both the Form.TransparencyKey and Form.Opacity use Windows Layers (see SetLayeredWindowsAttributes in the Platform SDK at http://msdn.microsoft.com/library[^]) with either the LWA_COLORKEY or LWA_ALPHA flag, respectively. For transparency keys, a COLORREF is used, which is a typedef for a DWORD, a 32-bit unsigned integer. The COLORREF documentation states that the high-order byte must be zero (the normal alpha byte) but as long as it is zero, I don't see why a graphics card in 32-bit mode would cause problems. Perhaps driver problems?

In any case, you can use the old way: window regions. You must override painting (override OnPaint in your form) and set the Graphic.Clip property to a region (use GraphicsPath to create an odd region) that determines which region is valid for painting. Everything else is not painted and, hence, shows what's behind it. This was really the only way to do it before Window Layers, which is only supported in Windows 2000 and higher.

The thing that puzzles me is that Windows Media Player skins use a color mask. Logically, that color would be the transparency color used with Windows Layers. Perhaps they are only using that color to designate a clipped region.

Re: Non-rectangular Windows :: the 24-bit issue [advanced]

leppie8-Jan-04 8:17

Generating strings that are matched by a regex

8-Jan-04 8:17

nibmike wrote:
This works fine, however msdn claims that non-rectangular windows wont work on graphics cards currently displaying more than 24-bit colour, which is true.

Isnt that 24-bit and less? True transparency only works on 32-bit ARGB and indexed palleted formats like GIF.

leppie ::AllocCPArticle("Zee blog");
Seen on my Campus BBS: Linux is free...coz no-one wants to pay for it.

bnieland8-Jan-04 6:34

bnieland

8-Jan-04 6:34

Folks,

For bizarre reasons, I need to be able to generate random strings that will be matched by a given regex.

i.e. given [a-z][a-z1-9][qrst]
I want an algorithm that will generate

abs
z9q
dvt

et cetera...

Anyone hear of anything similar? Or maybe you know a simple regex parser that I cannibalize?
(C# preferable, or a C related language)

Thanks,

Brett

DTrent

Re: Generating strings that are matched by a regex

Kentamanos8-Jan-04 6:58

Kentamanos

8-Jan-04 6:58

It's obviously pretty easy to code one for each individual regular expression by hand, but something that generates a random string for ANY given regular expression seems like it would be fairly complicated. I'm pretty sure there's nothing in the base classes for this. It would definitely have to understand the regular expression syntax you're using.

How would you handle something like:

[a-z]*

That means zero to "infinite" lower case letters basically. Would your random generator have an upper limit on cases like that? Would you want zero's to occur more often than other numbers?

I wish I could help more, but I've never heard of anyone doing this (haven't really searched or anything though). Let me know how it turns out.

Re: Generating strings that are matched by a regex

leppie8-Jan-04 7:04