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This is what I am doing to use threading to populate a listbox.
Question:
Do you know how I can write to the text of the winform? i.e. this.text fails
//Thread...
private System.Threading.Thread t = null;
delegate void AddToListDel(string text);
private void AddToListbox(string text)
{
if (this.lstProfileInsertStatusError.InvokeRequired)
{
AddToListDel a = new AddToListDel(AddToListbox);
this.lstProfileInsertStatusError.Invoke(a, new object[] { text });
}
else
{
this.lstProfileInsertStatusError.Items.Add(text);
}
}
private void myButton_click()
{
t = new System.Threading.Thread(new System.Threading.ThreadStart(this.GetProfileElementsValues));
t.Start();
}
private void GetProfileElementsValues()
{
//this line works
AddToListbox("START TIME : " + DateTime.Now.ToShortTimeString());
//this line fails
this.text = "processing " + i;
}
Any thoughts on how to solve this issue please?
I believe I need to have something similar to AddToListbox(string text) but for the text of the form?
Thank you
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Yup, you're not allowed to modify the variables of other threads without locking. Imagine you and me as a thread. You own a car (that's one of your variables). Obviously, we can't drive at the same time. That's why you get an error; I'm not allowed to start steering, without asking you first.
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You can only access the controls from the thread that created them, i.e the main thread.
There are basically two ways of doing that:
1. Use Invoke to make the main thread execute the code, just like you do in the AddToListbox method. If you know that you are always doing that from a background thread, you don't have to check the InvikeRequired property, but just invoke the code directly.
2. Put the data in a synchronised variable (use the lock keyword to synchronise both when reading and writing), where the main thread can look for it and put it in the control.
Despite everything, the person most likely to be fooling you next is yourself.
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What you need to do is add a check if an invoke is required change the text from the main thread by invoking it. To do an invoke you need to do 3 things:
1. Create an EventHandler.
private delegate void SetTextValueHandler(string value);
2. Create a function whose signature matches the delegate and does what you want.
private void SetTextValueToConsole(string value)
{
this.text = value;
}
3. Change the line that fails to something like this:
if(this.InvokeRequired)
{
this.Invoke(new SetTextValueHandler(SetTextValueToConsole), new object[1] { "processing " + i.ToString()});
}
else
{
this.text = "processing " + i.ToString();
}
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You are welcome 
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Hi, I've read a lot of documents on capturing images and video from webcams and even some of multiple webcams. There are many questions on the web and few answers.
I am trying to implement this but am having trouble finding the right information. From my understanding the best way is using directshow when using multiple cameras. Thats fine but why can I not do this using WDM or VFW or can I?
Any help greatly appreciated. Thanks in advance....
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How can I detect when a user has selected a different row to the current row?
I want to enable/disable toolbar 'Next' 'Previous' buttons in toolstrip based on selection location within grid.
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SelectionChanged event by any chance?
Bob
Ashfield Consultants Ltd
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Ashfield wrote: SelectionChanged event by any chance?
I was going to suggest video surveillance but I think your solution is better. 
led mike
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led mike wrote: video surveillance
I think its neater, but its been a long day....
Bob
Ashfield Consultants Ltd
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I have one Master page in master page i have create menu using link button and i have apply Same Css on All.
And I have 5 content page.
I want when my content page one is load Then Change CSS of specify link button.
I Try This Code But this Code not Working properly.
protected void Page_Load(object sender, EventArgs e)
{
MasterPage pharmacyMaster = (Pharmacy_ICaremaster)this.Master ;
LinkButton mastrlbtnCategory = pharmacyMaster.FindControl("lbtnCategory") as LinkButton;
mastrlbtnCategory.CssClass = "cssAMainLink:visited";
}
how Can I Do It.
Reply urgently .
thanks in Advance.
Ishtiaque Hussain Jalbani.
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how about asking this in ASP.NET Forum ...
If You win You need not Explain............
But If You Loose You Should not be there to Explain......
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Head off to the ASP.NET forum.
xacc.ide - now with TabsToSpaces support IronScheme - 1.0 beta 1 - out now! ((lambda (x) `((lambda (x) ,x) ',x)) '`((lambda (x) ,x) ',x))
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I am trying to control a service remotely, by impersonating (basically using this technique: http://www.codeproject.com/KB/dotnet/UserImpersonationInNET.aspx[^]) an administrator of the remote computer and using the ServiceController classes.
The problem is that i can't start or stop the services, I can however enumerate them fine. If i add my local account as an administrator on the remote computer, and turn off impersonation I can start and stop.
Any idea why? Does impersonation not do the job?
plz halp
betonglasermur.FeedDwarf(pur_is, 17);
ProcessStartupInfo.AintNotCreateNoWindow = (false && !true) != (true || false) ? false == true ? true : false : (true != false && false);
Morgonen är tröttmans mecka
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Hello everyone,
I have a very simple data structure representing a book, including ID/title/author/price, no more big field, all are strings. My application provides simple interface to query book information by book ID.
1.
And I want to store book information into Dictionary, book ID as key and other data as value. My question is are there any best practices about the size of a Dictionary should be? The total data is very big (a couple of G bytes monitored from physical serialized file), and I am not sure whether I should divide the data into several Dictionary or just use one?
2.
Does Dictionary use page file to swap storage (e.g. Dictionary could be able to store more information than physical memory limitation of current computer if it could use swap page file) or just use pure memory?
thanks in advance,
George
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Hi George,
I haven't used any memory-based data structure larger than my system's physical
memory, and I don't plan to do so any time soon: the data structure would be
loaded into (virtual) memory and immediately swapped out to the page file on
disk again, yielding bad system performance.
Whenever you need large amounts of data, and certainly if you are using
only small parts of it at a time, use a database. SQLServer Express is freely
available, and SQL queries can be organized in all popular .NET languages.
BTW: A dictionary is no different from any other data structure as far as memory
behavior goes; data structures don't decide themselves on whether they get
swapped out. It is the memory manager that decides on these mathers,
irrespective of the structures or classes involved.
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Hi Luc,
To tell the truth, my SQL is very bad and I just want to skip to learn it.
So, your point is Dictionary could use page swap file and could contain more data than physical memory?
regards,
George
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Hi George,
George_George wrote: Dictionary could use page swap file and could contain more data than physical memory?
technically yes (and so could a byte array, or anything else).
and practically no, you will probably not be satisfied by the performance
of your app.
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Thanks Luc,
You mean even if page file enables us to use larger memory than physical memory limitation, the access is slow?
regards,
George
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Hi George,
I assume your data is on disk somehow. So populating a data structure
(Dictionary or anything else) first will read the data from disk; since
this overflows the physical memory, it will spill over to the page file(s),
so performance will resemble a huge file copy before anything useful will
be possible.
If you could skip the "load all data first" step, you would not incur
this penalty. The easiest way to do this, is by using a database.
The database code is smart enough to cache data, and uses available
memory in an optimal way.
Also, when the application is very simple (so you could do without
a database), then the required SQL will also be very simple. Maybe
you just need a single table, and a single SELECT line, as in
SELECT * FROM books where books.ISBN = '1234-5678-1234'
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Keep in mind that a database will use SEVERAL TIMES as much memory as your raw data, due to overhead (indexing etc...). A hash table will give faster retrievals and allow you to store more data in memory.
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Thanks Alan!
Any ideas to my question below?
--------------------
And I want to store book information into Dictionary, book ID as key and other data as value. My question is are there any best practices about the size of a Dictionary should be? The total data is very big (a couple of G bytes monitored from physical serialized file), and I am not sure whether I should divide the data into several Dictionary or just use one?
--------------------
regards,
George
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Thanks Luc,
I am considering using SQL solution seriously. And I am also interested to do benchmark.
One more question, in my scenario is it better store all data inside one Dictionary instance or split into a couple Dictionary instances (e.g. Dictionary instance to store book name starts with letter A, instance with letter B, etc.)? Any best practices about the size of Dictionary which should not exceeds?
regards,
George
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