Joining two DataTables to a CheckListBox control... - C# Discussion Boards

Listing Items Alphabetically in TreeView

cAptHiDDeN3-Jul-02 4:48

3-Jul-02 4:48

Hi,

Does anyone know if there is an update function in C# that will allow a TreeView to be sorted alphabetically? I have items being added to my tree but they just aren't being listing alphabetically. If I close my program out and rerun it -- it is then that they are listing alphabetically. Did I miss something? Any help would be greatly appreciated. Thank you.

cAptHiDDeN Poke tongue | ;-P

Transparent User Controls

2-Jul-02 11:21

Hi,

I would like to create a simple user control. It only should draw a border. I did that, added it to the toolbox, used it, and it was no problem.

But:

I would like my user control to be transparent, so that the background of the parent form is visible everywhere my user control does no drawing.

Hope you understand and give me an advise.

Thanks

Localization in ASP.NET

2-Jul-02 5:08

I don't know how to do Localization in ASP.NET, if somebody has an example please provide.

Thanks in advance.

TEXTBOX

vikramlinux2-Jul-02 3:32

vikramlinux

2-Jul-02 3:32

I have one c# form and a textbox on it. I want to accept only numric values through it .
Is there any such control property? Frown | :(

VIKS

Re: TEXTBOX

Chris Rickard2-Jul-02 4:11

Chris Rickard

2-Jul-02 4:11

Not built in. You can find various masked inputs that other people have made, or you can override OnKeyPressed and OnTextChanged to cancel any non-numeric input.

Re: TEXTBOX

vikramlinux2-Jul-02 5:48

vikramlinux

2-Jul-02 5:48

Thanx for the reply. Blush | :O

VIKS

Re: TEXTBOX

Sorin Comanescu3-Jul-02 22:42

Sorin Comanescu

3-Jul-02 22:42

You can use regular expressions to control the input; here you can find a short tutorial with examples for regular expressions: http://www.c-sharpcorner.com/3/RegExpPSD.asp

Joining two DataTables to a CheckListBox control...

Andrew Connell2-Jul-02 3:28

Andrew Connell

2-Jul-02 3:28

My situation is that I have two tables: tblKeyword and tblProjectKeyword.
tblKeyword contains a list of available keywords (intKeywordID, txtKeyword).
tblProjectKeyword (intProjectID, intKeywordID).
tblProjectKeyword.intKeywordID is a FK to tblKeyword.intKeywordID.
tblProjectKeyword.intProjectID is also a FK to another table. So the
tblProjectKeyword table is a Many-Many relationship... a join table.

What I'd like to do is bind the contents of tblKeyword to a CheckListBox
control but have all the matching records in tblProjectKeyword appear
checked for a specific project. My keywords work similar to the Categories
window in Outlook items... the user will be able to check/uncheck and add
more keywords to the list.... So, the CheckedListBox would contain ALL
keywords, and have only those in the tblProjectKeyword checked. Additions
to the list would be added to the tblKeyword table and checked items would
be added to the tblProjectKeyword table.

Currently I'm implementing this manually (creating all the items... when one
is checked, I add a record to the table, etc, etc). I was wondering if I
could use databinding with this complex example. I know you can bind a
table to it, but I didn't know if I could bind two tables with some specific
conditions.

Currently, I am binding the tblKeyword table to the control.. then stepping
through everything in the list, checking to see if it's in the tblProjectKeyword list, and checking those that are found. When the checked state changes, I manually add/delete items to the tblProjectKeyword Datatable.

Thanks for your input in advance!
AC

Andrew Connell
IM on MSN
andrew@aconnell.com

All treenodes in a treeView

2-Jul-02 1:20

how do i get all the treenodes in a treeview including the subdirectories??

treenodecollection = treeview.topnode.nodes return only the child nodes of the topnode and doesnt include the subdirectories.

i = treeview.topnode.getnodecount(true) does return the count but doesnt seem to return the nodecollection as such.

Is there any method available or it has to be implemented recrusively.

thanks.

Re: All treenodes in a treeView

James T. Johnson3-Jul-02 8:58

James T. Johnson

3-Jul-02 8:58

I believe you'll have to loop through the node collection for each node.

James
"Java is free - and worth every penny." - Christian Graus

The C# using operator

Chris Maunder1-Jul-02 15:47

Chris Maunder

1-Jul-02 15:47

I'm just wondering about the C# using operator and what it means in terms of style.

In C# you can either do:

Font font = new Font("Arial", 10.0f);
// use font
...
font.Dispose(); // free resource
// garbage collector will clean up memory

Font font = new Font("Arial", 10.0f);
using (font)
{
    // use font
    ...
}
// compiler automatically calls font.Dispose();
// garbage collector will clean up memory

Has anyone used the using keyword? If so, why? For convenience? Style? For fear that IDisposable may be changed in future releases and using will still work while Dispose may not?

Just curious.

cheers,
Chris Maunder

I spent a minute looking at my own code by accident. I was thinking "What the hell is this guy doing?" - @Logan

Re: The C# using operator

Andy Smith1-Jul-02 16:03

Andy Smith

1-Jul-02 16:03

a using statement written like this:

using( Font font = new Font("Arial", 10.0f) ) {
// use font
}

actually translates to this:

try {
Font font = new Font("Arial", 10.0f) );
// use font
} finally {
if ( font != null ) {
((IDisposable)font).Dispose();
}
}

now i don't know about you...
but i find the "using" method much clearer and easier to read.

Re: The C# using operator

Rama Krishna Vavilala1-Jul-02 16:05

Rama Krishna Vavilala

1-Jul-02 16:05

Except that if there is more than 1 resource it gets ugly.

Re: The C# using operator

Chris Maunder1-Jul-02 16:25

Chris Maunder

1-Jul-02 16:25

Excellent point.

It's strange that in C++/SDK code you rarely see developers checking every return code and every HRESULT to ensure that things are going smoothly. I wonder if constructs like using will enourage more developers to be a little more careful.

cheers,
Chris Maunder

I spent a minute looking at my own code by accident. I was thinking "What the hell is this guy doing?" - @Logan

Re: The C# using operator

Rama Krishna Vavilala1-Jul-02 16:03

Rama Krishna Vavilala

1-Jul-02 16:03

I liked it initially but it really gets ugly for nested loops and more than 1 resource. C++ smart types are far better. I prefer to use try {} finally {} now.

Re: The C# using operator

Nish Nishant1-Jul-02 16:08

Nish Nishant

1-Jul-02 16:08

This might be a stupid question. But why call Dispose manually? Isnt that what the GC is for? Or are we talking about freeing GDI resources here?

Nish Confused | :confused:

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Re: The C# using operator

Andy Smith1-Jul-02 16:12

Andy Smith

1-Jul-02 16:12

the garbage collector is for handling memory, not scares resources like GDI stuff, file locks, and database connections.

Re: The C# using operator

Nish Nishant1-Jul-02 17:15

Nish Nishant

1-Jul-02 17:15

Andy Smith wrote:
the garbage collector is for handling memory, not scares resources like GDI stuff, file locks, and database connections.

But even those will eventually get deleted.

Nish

Author of the romantic comedy

Summer Love and Some more Cricket [New Win]

Review by Shog⁹
Click here for review[NW]

Re: The C# using operator

Andy Smith1-Jul-02 17:28

Andy Smith

1-Jul-02 17:28

maybe, but not neccessarily before somebody else NEEDS that resource NOW.

GC is designed to handle memory deallocation. It's not really designed to handle database connection management. that's oledb's responsibility, and it would do it much better than any generic garbage collection could.

Re: The C# using operator

Rama Krishna Vavilala1-Jul-02 16:17

Rama Krishna Vavilala

1-Jul-02 16:17

GC process doesnot call Dispose it only calls Finalize. Dispose is to free resources.

In Finalize you can free only unmanaged resources and not managed resources. So in case of Font this is ok but again it takes time. I prefer to clean up stuff myself.

More important is freeing managed stuff. (I realized this after seeing areecnt thread in DOTNET list).

StreamWriter writes text in buffers. The buffer is a byte array. So in Finalize you can't flush the buffer. So the only place where you can flush the buffer is Dispose/Close. In these cases you need to call Dispose/Close.

May be our resident C# specialist JTJ can add more to it Smile | :)

Re: The C# using operator

James T. Johnson1-Jul-02 17:15

James T. Johnson

1-Jul-02 17:15

You pretty much summarized the reason to explicitly call Dispose on objects that implement it Smile | :)

One thing I noticed though; was you said it can make the code ugly if you have multiple objects to call dispose on; you can simplify it; if they are in one block.

Font f = ....;
Brush br = ....;
Bitmap bi = ....;

try
{
  .....
}
finally
{
  f.Dispose();
  br.Dispose();
  bi.Dispose();
}

Could become

using(Font f = ....)
using(Brush br = ....)
using(Bitmap bi = ....)
{
  .....
}

Which is much much cleaner than the mass indentation you would get otherwise. Smile | :)

James
"Java is free - and worth every penny." - Christian Graus

Re: The C# using operator

Rama Krishna Vavilala6-Jul-02 16:06

Rama Krishna Vavilala

6-Jul-02 16:06

using(Font f = ....)
using(Brush br = ....)
using(Bitmap bi = ....)

This works. But unfortunately, the generated code still has 3 try{}finally{} blocks.

Re: The C# using operator

Andy Smith1-Jul-02 16:15

Andy Smith

1-Jul-02 16:15

um, could you give me an example of ugliness?

the more resources "used", the more code it autogenerates for you!

the using statement lets you focus on the intent of the code instead of the mundane plumbing.

Re: The C# using operator

Rama Krishna Vavilala1-Jul-02 16:25

Rama Krishna Vavilala

1-Jul-02 16:25

It's a matter of personal preference

File f1 = null;
File f2 = null;

try
{

}
finally
{
if (f1 != null)
f1.Dispose();

if (f2 != null)
f2.Dispose();
}

using(f1 = new File(..))
{
using(f2 = new File(..))
{
}
}

I prefer the former.

Re: The C# using operator

Andy Smith1-Jul-02 16:29

Andy Smith

1-Jul-02 16:29

um... you can put both in the same using statement parens.
so it becomes

using(
Font f1 = new File(..),
Font f2 = new File(..)
) {
// do your thang
}

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