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Or you could instantiate a new Dictionary, then iterate the existing one, adding the items you do want to the new one.
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That could be done, but it would seem rather wasteful.
In nearly all common practical algorithms for storing collections, support for DeleteAndMoveNext could be added relatively simply. In many cases, it would add no extra work to the iterator's normal operation; in others, it would add a small amount of work (e.g. a singly linked list would need to keep a pointer to the item before the current one). Given the number of tasks that require striking from a collection objects which meet a particular criterion, and given that an iterator will often have information that would facilitate the deletion of an object from a collection, having an extended iEnumerator interface would seem useful.
BTW, for some types of collection, where the enumerator contains all the information about an object (e.g. a KeyValuePair) it may be useful to have general-purpose Add and Delete functions within the enumerator itself. Such functions would invalidate any other enumerators to the root object, but would do whatever was necessary to maintain their own validity. Not sure that would have much added utility beyond DeleteAndMoveNext, though.
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supercat9 wrote: Use of that method would remove the currently-selected item from the collection and
...invalidate the Enumerator all in one shot. As you've found out, you cannot modify a collection during an Enumeration ("for each" operation).
The only solution would be to use in Indexed (for(i=0;i<10;i++) item(i)...) operation, treating the collection as an array instead.
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Dave Kreskowiak wrote: ...invalidate the Enumerator all in one shot. As you've found out, you cannot modify a collection during an Enumeration ("for each" operation).
The whole idea of having an object return an enumerator that supported a DeleteAndMoveNext object would be that such a function would do whatever was necessary to avoid jinxing the enumerator. Note that the DeleteAndMoveNext would not be a general-purpose delete; it could only delete the current object. A simple implementation for an array-based list, if one wanted deletes to be performed immediately, would be to move down all objects above the present object, without bumping the object index. A singly-linked list object whose iterator kept a pointer to the previous object could 'swing' that pointer to point to the object following the present one and then advance the present object (note that this would be much faster than doing a search-and-delete).
An alternative general approach to allow deletions while traversing an iEnumerable object would be to have the 'delete' function mark an item as invalid (using either a 'valid' flag or a sentinel value) and also set a flag in the collection to indicate that one or more deletions had taken place. If 'add' operations are not allowed during an enumeration, the next add operation could check whether any items are marked for deletion (using the collection's flag to start with) and then remove all items that are so marked. For an array-based implementation, this could be much faster than having all deletes performed 'instantly'.
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Hi,
two comments:
1.
I too would like to have a non-resettable enumerator that remains operational when elements
are modified, deleted or new ones inserted at a point that has already been passed.
2.
There is a nice List.RemoveAll() Method that accepts a predicate. That should solve your problem.
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Luc Pattyn wrote: There is a nice List.RemoveAll() Method that accepts a predicate.
Good to know. Unfortunately I need a collection that behaves like a dictionary. Perhaps the best approach would be to have something that's like a dictionary with the addition of RemoveForAll; unfortunately I know no good way to adapt the existing dictionary to fit that need except by having the removeForAll create a list of keys of objects to be deleted, which would likely take time n^2.
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In case of typed dataset I want to pass as an array to the typed dataset so that i can have the all data of selected code in arrays filled in dataset
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Hello,
I have to display HTML in desktop application. Not only a simple text but also images and maybe flash elements and movies... Problem is because the background is an image and the browser background must be transparent.
I tried several solutions but all of them failed...
Have You ever had the same problem or do You konw any solution? It may be even payable .NET control.
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I've never seen, nor heard of, a browser control that is transparent to the form. I think you're going to have to write this one yourself.
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I was really affraid to hear that there is not such component...
I've got idea how to write transparent browser, but I'm concerned about "blinking" effect... GDI+ is not a speed demon...
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hello,every expertist
From debug the program, System shows if(dr.read()) == false, by the way, sql sentence is correct, test in SQL2005 Successfully!
i really confused, help me! Thank you!
private void button13_Click(object sender, EventArgs e)
{
if (this.textBox1.Text.Length > 11)
{
MessageBox.Show("please input correct number ",MessageBoxButtons.OK,MessageBoxIcon.Error);
this.textBox1.Clear();
}
else if(this.textBox1.Text.Length < 11)
{
MessageBox.Show("please input correct number ", MessageBoxButtons.OK, MessageBoxIcon.Error);
this.textBox1.Clear();
}
else
{
string sql = "select * from customer_colorring where cmobilephone ='" + this.textBox1.Text + "'and documentfile = 'g:\\song\\when i meet you.mp3'";
CDBSql q = new CDBSql();
SqlDataReader dr = q.getDataReader(sql);
if (dr.Read()) //here shows false,why????????????????????????????????????
{
string file = q.getScalar(sql).ToString();
Media.MP3Player mp3player = new Media.MP3Player();
mp3player.Open(file);
mp3player.Play();
mp3player.Pause();
mp3player.Stop();
mp3player.Close();
}
else
{
MessageBox.Show("no songs","error",MessageBoxButtons.OK,MessageBoxIcon.Error);
}
}
}
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Try adding a space in "'and
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Hello !
I'm a Chinese, i want to know how to use checkbox in datagridview. For example, there are 10 records in the datagridview, and i want to delete or modify them by clicking checkbox and a button. the checkbox is used for selecting the records,the button is used for deleting the records, i don't know how to write the codes.
if you know,please tell me, Thank you very much!
My e-mail address is : xurf@js.chinamobile.com
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bozin wrote: i don't know how to write the codes.
What is going on here? Has someone outsourced this project to you? What are the requirements?
led mike
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hello,led mike
no,i just do an exericise, not a project. simply speaking, i added checkbox to the datagridview checkboxcolumn, and when the checkbox is checked,and press "delete" button, the selected record will be deleted.
i want to know how to write the codes? if i write codes for "delete" button
private void button1_Click(object sender, EventArgs e)
{
// here i can't find the something about checkbox,so i have no ways to continue!
}
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bozin wrote: no,i just do an exericise
Are you working through some sort of tutorial or Article? If not you should be, there will be many on the internet probably even some articles here on CodeProject.
led mike
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i do that stuff (delete/add/edit row) directly to the database! sql server database (or a xml file!).
for exemple i delete a row in the database (not in the dgv) and afterwords refresh the dgv.
there´s no sense to me, to add or delete records in the dgv you know.
See you can do that but when you run the application other time the changs aren´t there so like i said i edit the database (not the dgv) and after i refresh dgv everytime i do my changes.
about the buttons, create a panel and place inside the dgv and a toolstrip with buttons for the operations you want, and textboxes for each column in the dgv, these textboxes will get the current row data, ok? here the id textbox get´s the current row (selected row in dgv) so that´s a easy way to get the row selected better that checking boxes.
little of coding there 
nelsonpaixao@yahoo.com.br
trying to help & get help
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Hi all,
I have created an Excel 2003 AddIn project and created one Setup project also for install the AddIns in target machines. My setup contains the primary out put of the AddIn project. I just came to know some registery entries are required for successful installation. Can any one help me in creating setup project with necessary registery entries.
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using keypress iam handling user not to allow any special characters in the textbox
now how can i disable paste event for the textbox
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Supress Ctrl + V keypress for the textbox and re-initialize its context menu.
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You will have to research overriding the WndProc function when inheriting from a textbox control.
Regards,
Thomas Stockwell
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.
Visit my Blog
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MSDN DataGridView VirtualMode with caching sample code DataRetriever loads two pages always to cache thus making 2 database accesses.
If datagridview uses one page of data, second page retrieval is unnessecary and makes DataGridView display 2 times slower.
How to change this sample code so that only one page is loaded initially and second is loaded on real demand only ?
How to change this code so that it allows more than 2 pages of cached data? 2 page limit seems to be hardcoded into this page.
Or is there some other sample code which has solved those issues ?
Andrus.
Andrus
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hello fellas and programmers,
hi,i am working on an application which stores details in a database and then displays on a datagrid.how can i then print the info/details from the datagrid.pls reply with an example showing the codes used or rather if u have an application displaying the codes in a pdf file, i'll reaLLY APPRECIATE it. Thank you.
topzturvy
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There are two issues :
1. My windows application contain many number of controls like, buttons, textboxes,checkboxes etc..
Application is very slow while execution and even for any button click event application hangs for a while(atleast 8 seconds).
Used panel and group box but same status.
2.While execution i have to show one progress bar for particular button click event. And need to increment progress bar in sync or simultaneously with button click event execution.
Example: (only a part of the code i am writing here in blog):
Two forms form1 & form2:
on form1 button click event some code is executed.
say form1 code:
form2 trs = new form2();
btn_click
{
trs.Show();
trs.Owner = this;
trs.go(this);
Thread thred = new Thread(new ParameterizedThreadStart(trs.go));
string strngmain = "a";
....do something........(here actual code executes, while this executes,i want to show the status in progress bar, so while execution i am adding one char to string variable strngmain)
}
written one method in 1st form:
public void UpdateProgress(int progress)
{
if (InvokeRequired)
Invoke((MethodInvoker)delegate() { trs.progressBar1.Value = progress; });
else
trs.progressBar1.Value = progress;
}
where 'trs' is a instance of form2 declared in form1.
No. of times 'a' char is added in single button click event to a string declared called "strngmain". And depending upon each char progress bar status should get incremented in 2nd form.
Form2: It contains one progress bar which should increment depending upon the button click event execution:
Code in form2:
form2_load
{
progressbar1.show();
}
public void go(object param1)
{
MainForm form = (MainForm)param1;
string strng;
srtng = ((MainForm)this.Owner).trans_complete;
foreach(char c in strng)
{
form.UpdateProgress(10);
Thread.Sleep(10);
}
}
But the above code is not working correctly , progress bar is not incrementing in sync with mainform's button click event code execution.
Any help appreciated.
Thanks in advance.
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You are going about it in the wrong way. Look into using a BackgroundWorker. It is meant to due computations in the background and relaying progress information to the GUI without freezing the application for awhile.
Regards,
Thomas Stockwell
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.
Visit my Blog
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