Re: problems with memory. - C# Discussion Boards

Re: binding individual columns of a datgrid to a dataset/datatable

19-Mar-07 23:59

ya sure.
well here is my case.

i have a database, which has several columns. I need to modify the contents of a single column. Looking at a different side, binding a single column to a separate data source doesnt make sense to me either.

what I really want is to modify the contents of a cell of a column of a datagrid.
Can i do it using a datatable or a dataset, coz it is much faster, than accessing a datagrid as Datagrid1.Rows[i].Cells[j].

m trying to modify a cell. how to do it, if i bind a datagrid to a datatable.

Keshav Kamat Smile | :)

India

joon _vh.20-Mar-07 0:08

joon _vh.

20-Mar-07 0:08

You can edit individual cells in DataTables in the same way as you edit cells in a DataGridView.
You can (or have to) use DataTable.Rows[i].Cells[j]...

public object BufferOverFlow<br />
        {<br />
__get { return BufferOverFlow; }<br />
__set { BufferOverFlow = value; }<br />
}

Re: binding individual columns of a datgrid to a dataset/datatable

Keshav V. Kamat20-Mar-07 0:44

Re: binding individual columns of a datgrid to a dataset/datatable

20-Mar-07 0:44

well ok.

as u said in the previous replies,
when i try to bind a datagrid to a data table and try to access the cell or the row count of the data table, it says object reference not set. it comes null.

here is how i try to bind a datagrid to a datatable.

DataTable dt1=new DataTable("dt1");
dt1 = (DataTable)LoggerDatagrid.DataSource;

please tell me, if I am making a mistake anywhere.

thanks in advance.

Keshav Kamat Smile | :)

India

Pualee20-Mar-07 1:14

Pualee

20-Mar-07 1:14

I have not read the whole thread, but what comes to mind first is, have you looked in the following:

http://www.codeproject.com/books/PresentDataDataGridView.asp[^]

I found that little gem yesterday trying to solves some other issues.

Pualee

Re: binding individual columns of a datgrid to a dataset/datatable

joon _vh.20-Mar-07 1:59

joon _vh.

20-Mar-07 1:59

You're doing it the wrong way around.
It should be :

LoggerDatagrid.DataSource = dt1;

now your datagrid should be populated, and then you can start looking for cells to edit.

Visual Studio can't evaluate this, can you?

public object moo<br />
        {<br />
__get { return moo; }<br />
__set { moo = value; }<br />
}

problems with memory.

Duong Tien Nam19-Mar-07 23:25

Duong Tien Nam

19-Mar-07 23:25

I have some problems with destroying object after using.

1. How can I dispose the form with many events registered and some global fields that has to be destroyed? Or it will destroy automatically?

2. If my class registers some events from other objects (use +=), do I have to unregister all the events (use -=)on its Dispose() method? I afraid that the objects firing events will stay still in heap if I dont do that.

Thx for you answers.

Pualee20-Mar-07 1:22

Pualee

20-Mar-07 1:22

How do you know you have a problem? What are the symptoms?

It is my understanding that all managed references are cleaned up automatically, however, if you look up discussions online, you will see everyone argues about whether or not to call dispose() explicitly. Personally, I don't clean up unless I know its necessary, ie calling Close() on a connection. Even this doesn't really close the reference, but just frees it back to the connection pool.

Pualee

J4amieC20-Mar-07 2:02

J4amieC

20-Mar-07 2:02

Pualee wrote:
about whether or not to call dispose() explicitly

Anyone saying you should not call Dispose explicitly is wrong wrong wrong!

---

How to get answers to your questions[^]

Pualee20-Mar-07 2:23

Pualee

20-Mar-07 2:23

For my personal education, would you care to elaborate. This is a topic I have really been trying to grasp lately. I come from a different environment where I would expect to clean up all my references, but in C# I thought this was automatic. As stated earlier, I see strong opinions on both sides.

Is calling Dispose() just good practice, or is it actually necessary to prevent memory leaks and other problems?

Thanks,
Pualee

J4amieC20-Mar-07 8:29

J4amieC

20-Mar-07 8:29

It is just good practice.

As long as you are in managed code only (ie no unsafe code) memory is 100% managed for you.

---

How to get answers to your questions[^]

How to Drag and Drop items from a ComboBox to a treeview?

Luc Pattyn21-Mar-07 15:00

Luc Pattyn

21-Mar-07 15:00

I disagree, it is not just good practice.

Calling Dispose on instances of a class that has a Dispose() method is mandatory;
the class may or may not hold unmanaged resources (encapsulation makes that
knowledge irrelevant), and Dispose() would take care of them.

So there are two basic rules:
- if you design a class that holds unmanaged resources, you MUST provide a
Dispose() method
- if a class offers a Dispose() method, you MUST call it when (or as soon as)
you are done with its instance(s).

Hope this helps.

Luc Pattyn

[My Articles]

Starzfighter19-Mar-07 23:04

Starzfighter

19-Mar-07 23:04

Hi again. I have a little problem with Drag and Drop.
I like to Drag an item from a comboBox to a Treeview. The item then should be displayed as Node in there.
Does anyone have suggestions how to do that?

I tried the following:

private void comboBox1_MouseDown(object sender, MouseEventArgs e)
{

if(comboBox1.Items != null)
{
comboBox1.DoDragDrop(dv[lc.SelectedIndex].Row["Typename"].ToString(),DragDropEffects.Copy);
}
}

But now when i click on the comboBox the List does drop down only for a milisec. So i can't select any other item then the first in the list.
Anyone any ideas?

Would be glad if anyone could give me some additional tips about drag and drop from a comboBox to a Treeview.

Re: How to Drag and Drop items from a ComboBox to a treeview?

joon _vh.19-Mar-07 23:22

joon _vh.

19-Mar-07 23:22

This article (you can search articles, there's a lot of them) I found right here on CP:

ListBox to TreeView Drag and Drop[^]

it's about a listbox, but I'm pretty sure its applicable.

public object BufferOverFlow<br />
        {<br />
__get { return BufferOverFlow; }<br />
__set { BufferOverFlow = value; }<br />
}

hi just make it

sooreeagt19-Mar-07 23:00

sooreeagt

19-Mar-07 23:00

i want the difference between dates in javascript...
like if i gave any date that should be compared with roday date and it should give the difference...

Suresh.R

blackjack215019-Mar-07 23:05

blackjack2150

19-Mar-07 23:05

Why are you posting this on a C# forum?

sujithkumarsl19-Mar-07 23:14

sujithkumarsl

19-Mar-07 23:14

Better to post this in javascript forun
in c# you can get time span by simply subtract the DateTime values

My small attempt...

PlayByTheRules19-Mar-07 23:23

PlayByTheRules

19-Mar-07 23:23

sooreeagt wrote:
hi just make it

Your title should reflect the problem you are having. It should NOT make demands of the other people using the forum.

sooreeagt wrote:
javascript

You should pick your forum more appropriately. Your question has nothing to do with C#

Keshav V. Kamat19-Mar-07 23:41

19-Mar-07 23:41

please seek an appropriate forum for the discussion.
your topic is not related to the one where you have posted.
Thanks.

Keshav Kamat Smile | :)

India

Ram Krishna Wagle20-Mar-07 1:18

Ram Krishna Wagle

20-Mar-07 1:18

Ye its pity to read out of context matters in the wrong place.
Make sure that doesnot happen again.

Your life is what your thoughts make it.

Help!

mihksoft19-Mar-07 22:59

mihksoft

19-Mar-07 22:59

Hy!
I want to make a comboBox and when I want to select I have some time in Items like
08:00 AM
08:30 AM
09:00 AM
but I want to have the possibility to introduce a time like 08:05 AM,

10x Big Grin | :-D

Mircea Puiu19-Mar-07 23:14

Mircea Puiu

19-Mar-07 23:14

Then you just have to get the text from the editor and add it to the collection of items in the combobox (in some combobox related event or when pressing some button).

SkyWalker

sujithkumarsl19-Mar-07 23:16

sujithkumarsl

19-Mar-07 23:16

sorry,Your question is not clear...............
Try with DateTime values

My small attempt...

PlayByTheRules19-Mar-07 23:26

PlayByTheRules

19-Mar-07 23:26

mihksoft wrote:
Help!

Everyone asking questions on this forum is looking for help. Please choose a more appropriate subject line.

Keshav V. Kamat19-Mar-07 23:32