Re: 2 projects 1 class - C# Discussion Boards

Re: Writing to a List box in a dirrerent form...

24-Jul-03 18:41

nevermind... you tell me how to do this 1 line down...

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eggie525-Jul-03 17:05

How can you tell if an element in a datagrid has the focus?

25-Jul-03 17:05

hmmm, it dosn't work...

do I have to place these any place special in my code... ?

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work_to_live24-Jul-03 12:05

work_to_live

24-Jul-03 12:05

I have a form with a number of user controls each derived from datagrid. I can't figure out how to tell which user control datagrid has the focus! I tried UserControl.Focused, and it returns false even if I select a cell within the datagrid. I tried overriding the UserControl.Focused property, extending the DataGrid.Focused value, and still no luck.

I'm relatively new to C#, so it's probably something simple related to derived controls.

Help!

Re: How can you tell if an element in a datagrid has the focus?

work_to_live24-Jul-03 13:31

work_to_live

24-Jul-03 13:31

Got it...
ContainsFocus indicates whether the control or any of it's children controls has the focus.

2 projects 1 class

albean24-Jul-03 10:45

24-Jul-03 10:45

I have one solution with two projects (project A & project B). Is there a way to "reference" a class in A from within B?

If I'm in project B and from the solution's explorer I choose "Add Existing Item" it copies the file from A's physical directory into B's directory.

I'm sorta trying to forward reference the class.

David Stone24-Jul-03 10:51

David Stone

24-Jul-03 10:51

Right click on project B, go to Add Reference..., go to the projects tab, select project A and add the reference. That should work. Smile | :)

I have also lived some years in Spain, and there people don't accept that you speak bad spanish. I usually compensate by speaking loud and accusing people of being stupid because they don't understand me. It usually works quite well.
-jhaga on non-native languages

albean24-Jul-03 11:06

24-Jul-03 11:06

Thanks, but Project A is not class lib (dll). Its an EXE that contains a class that I need to use in Project B.

Daniel Turini24-Jul-03 11:13

Daniel Turini

24-Jul-03 11:13

albean wrote:
Thanks, but Project A is not class lib (dll). Its an EXE that contains a class that I need to use in Project B.
You either make it a .dll or include the file as a link. On the "Add Existing Item..." dialog, do you see the small arrow on the "Open" button? Click it and select "Link file". This way, you'll create a link on your project B to the class on the project A. This will have the side effect of including the code of the class on the project B, too, but I think that this is exactly what you're looking for, right?

Acting as a substitute for God, he becomes a dispenser of justice. - Alexandre Dumas

David Stone24-Jul-03 11:46

David Stone

24-Jul-03 11:46

Why not create a shared dll that resides between them. That's what I usually do if I need to create two apps that share some of the same basic functionality.

albean25-Jul-03 9:19

accessing controls through a collection

25-Jul-03 9:19

Thanks David. That seems to do it.

Rbledwards24-Jul-03 10:44

Rbledwards

24-Jul-03 10:44

Hi, I am collaborating/taking over a project from another developer in my office. One part is a Windows form with a CheckBoxList controls on top and rows of ComboBoxes on bottom like this:

cbo1_1 cbo1_2 cbo1_3 cbo1_4
cbo2_1 cbo2_2 cbo2_3 cbo2_4
etc...

If there is anything selected in the CheckListBox then row 1 is enabled. More rows could be enabled depending on what exactly is checked.

The problem is that so much code is duplicated. For instance, each cbo is bound to a column in a dataset. For each cbo this code exists:
-------------------

private void Populatecbo1(System.Windows.Forms.ComboBox s)<br />
		{<br />
			s.Items.Clear();<br />
			int Count = _aColumn.Length;<br />
			for(int i =0; i < Count; i++)<br />
			{<br />
				s.Items.Add(_aColumn[i].ToString());<br />
			}<br />
		}

---------------------

and one for cbo2 and so on. Theres also literally thousands of lines of switch statements for enabling/disabling cbo's.

Isn't there a better way to do this without duplicating all of this code?

Thanks,

Robert

Re: accessing controls through a collection

Furty24-Jul-03 15:15

Furty

24-Jul-03 15:15

RblEdwards wrote:
Isn't there a better way to do this without duplicating all of this code?

Without seeing the full code it's not going to be possible to supply a working example, but the answer to your question given the information here is a resounding YES.

I would suggest creating an array of ComboBox controls, and iterating over them to populate them and set the Enabled property, there's a good chance you will be able to reduce it down to 3 or so methods.

e.g.

int cols = 10;
int rows = 10;
System.Windows.Forms.ComboBox[,] comboArray;
comboArray = new System.Windows.Forms.ComboBox[cols, rows];

Another possible option would be using a DataGrid to display the data and combo boxes (there's plenty of examples online for putting ComboBoxes in DataGrid cells), and simply manipulating the DataGrid properties to enable/disable item editing.

Re: accessing controls through a collection

LongRange.Shooter29-Jul-03 8:35

LongRange.Shooter

29-Jul-03 8:35

In addition to Furty's response...

If you have a collection of controls you can either populate them at
design-time (which leads to code like you've got) or you can programmatically add them yourself.

Try this:

Create a new project and put a GroupBox on the form
Add a single control to that GroupBox
Look at the Windows Generated code.

Now you have a template for what YOU would do, since the logic is adding a single control to the Control collection. Rip out the Windows generated code and make it a programmatic loop to add each control. Now --- if you have an event like having an item selected, point it to a single routine in your build code. If it is necessary to know which control from top to bottom was selected, you can interate through the Control collection until you find that control, and that becomes the index for populating the corresponding control in the other groupbox.

The beauty of reusability!

_____________________________________________
_{The world is a dangerous place.
Not because of those that do evil,
but because of those who look on and do nothing.}

Thread.Sleep is too slow

eggie524-Jul-03 10:26

24-Jul-03 10:26

I have Thread.Sleep in my program, and to fastest I can get it to sleep is 1 milla second...

I need it to be faster...

1 Micro second....

and way to do this?

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albean24-Jul-03 10:30

24-Jul-03 10:30

When Thread.Sleep is executed the .NET framework makes a system call that immediately causes a context switch. (AFAIK) Could you give a little more info about what you are trying to do?

eggie524-Jul-03 11:35

24-Jul-03 11:35

I just need my program to to pause... or delay... or wait.. for 1 micro second...

the Thread.Sleep can only go as fast as 1 milla second...

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albean24-Jul-03 14:26

24-Jul-03 14:26

If you just want a short "delay" then you do not want to use Thread.Sleep. Because even a Thread.Sleep(0) causes a context switch and it may take "a long time" for the OS to hand control back to your program, depending on how many threads/tasks are scheduled.

Perhaps there is a way to inline some assembly in a C# app (I don't know about this though) and you could execute a no-op or something that would fill your requirements for a delay.

But you will still have that context switching problem since windows is preemptive multitasking. Consider this:

1 Executing code
2 Executing code
3 Your Delay
4 Executing code
5 Executing code

Even if there were some (atomic) delay statement that you could use at step 3 a context switch could take place between 3 and 4. This would make your delay appear to be even longer.

Good luck though, maybe there is a workaround.

eggie524-Jul-03 17:36

24-Jul-03 17:36

ok, sleeping for (1) is one milla second right?

well what would (0) be? that's crazy... how long is 0? could that possibly be considered a micro second almost?

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albean25-Jul-03 9:09

25-Jul-03 9:09

Eggie,

You need to read about the Thread.Sleep method and more importantly what a context switch is.

Sleep( X ) means the thread will not be scheduled for execution by the operating system for X milliseconds. Sleep(0) causes the thread to be suspended (a context switch) and immediately rescheduled for another time slice. If there are no other threads at your thread’s priority level then it is executed.

The bottom line is you will not be able to create a delay to the precision you are looking for. (Well, you might be able to with in-line assembly but a context switch could occur and make the “delay” longer. And, now that I think about it, you will probably have to boost your thread’s priority. ) Sleep(0) is the shortest delay that I can think of but there is no control over its duration. Since there will be other threads waiting, they will all execute their time slices before yours gets the CPU back. I don’t recall what Microsoft has a time slice set at its probably around 50ms so if there are n threads scheduled before yours the delay will be n * ~50ms

In the post above Daniel wrote “More time resolution is only available with multimedia timers or DirectX.” He is right. What I’m speaking about is similar to you listening to music or watching a dvd on your computer. If you do anything that uses the CPU a lot, the music or movie becomes "choppy." That is, indirectly, related to the context switches that I’m talking about. Besides these context switches there are other things like interrupts going on(e.g. moving the mouse).

Anyway, there is always a workaround for coding problems.
Good luck.

BTW: You got me curious. Why do you need such a short delay for?

Context switch:
(this is just a summary, Google around for more details)
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/context_switches.asp

Sleep Method:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemthreadingthreadclasssleeptopic1.asp

eggie525-Jul-03 16:54

25-Jul-03 16:54

I'm making a program... well I have a program that sends data though the parallel port and stores it in the memory on my board...

The data is just a 50,000 line .xml file with a bunch of Hexidecmial.

Everything works fine... except I need that delay between bytes to be more precise...

I just downloaded the DirectX SDK, now I have to figure that out...

uh... anymore suggestions?

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LongRange.Shooter25-Jul-03 10:39

LongRange.Shooter

25-Jul-03 10:39

why not do a delay like the old way we'd do it in DOS?

DoProcess()<br />
DoProcess()<br />
DelayCode()<br />
DoProcess()<br />
<br />
<br />
<br />
public void DelayCode()<br />
{<br />
    for (int i=0; 1<1000; i++)<br />
        continue;<br />
}

_____________________________________________
_{The world is a dangerous place.
Not because of those that do evil,
but because of those who look on and do nothing.}

Daniel Turini24-Jul-03 11:15

Daniel Turini

24-Jul-03 11:15

Maybe Thread.SpinWait could help you.
More time resolution is only available with multimedia timers or DirectX.

Acting as a substitute for God, he becomes a dispenser of justice. - Alexandre Dumas

eggie524-Jul-03 11:33

24-Jul-03 11:33

Can it sleep from 1 micro second?

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