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Interesting. Not seen that before.
Regards,
Rob Philpott.
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It's a place holder that assigns an empty method - one that does nothing - to the event in case no handler method is ever assigned. That way, if it isn't used by the rest of the application, it doesn't crash when the delegate is used.
It's a bit like saying
List<string> list = new List<string>(); Instead of
List<string> list = null;
So when you use the collection:
list.Add("hello world"); You don't need to check that a list is assigned first to prevent your app crashing:
if (list == null) list = new List<string>();
list.Add("hello world");
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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thanks guys for the answers. It helps a lot.
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The new ?. operator alleviates the need for this. The recommended way of invoking an event handler is now
PropertyChanged?.Invoke(this, EventArgs.Empty);
(or whatever the arguments should be)
Cheers,
Mick
------------------------------------------------
It doesn't matter how often or hard you fall on your arse, eventually you'll roll over and land on your feet.
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the below code is working perfect for single item selection but i am unable to select more them one item and display corresponding data from database in datagridview.
SqlDataAdapter sda=new SqlDataAdapter();
DataSet ds=new DataSet();
SqlCommand scmd=new SqlCommand();
BindingSource bsource=new BindingSource();
private void button1_Click(object sender, EventArgs e)
{
int i = checkedListBox1.CheckedItems.Count;
if (checkedListBox1.SelectedIndex == -1 && checkedListBox2.SelectedIndex == -1)
MessageBox.Show("Please select");
else
{
for (int j = 0; j <= i-1; j++)
{
string s = "select * from grp where Groupname = " + "'" + checkedListBox1.CheckedItems[j].ToString() + "'";
sda = new SqlDataAdapter(s, con);
ds = new DataSet();
SqlCommandBuilder scb = new SqlCommandBuilder(sda);
sda.Fill(ds, "grp");
bsource.DataSource = ds.Tables["grp"];
dataGridView1.DataSource = bsource;
}
}
}
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You are resetting the data source of dataGridView1 each time round the loop, so it will only ever refer to the last one selected.
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Hi,
I am developing now an application that will generate barcode for items and I need the application to print this barcode and I don't have any experience how to integrate with printers.
My question what I need to use barcode printers?
Is this a straightforward? or need to know more about Printer API?
I've already see articles about specific model "EPSON L90" and its APIs but I need more examples to see how to walkthrough.
Thanks
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Start with the manufacturer's site: they will almost certainly have example code together with the appropriate API which will get you started.
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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Hi, I have been learning C# for over 6 months and learnt alot of it by building a text based RPG using SignalR to make it multiplayer. It's hosted on GitHub[^]
Wondering if anyone is interested in dropping in and helping me out by adding features, improving code, unit tests etc. It has a MIT license. Hoping someone better than me will contribute so I can learn the how and why off them.
Thanks.
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It might be worth moving this message to the "Collaboration / Beta Testing" forum. You'll find it under "Product Lifecycle" in the LHS menu.
Good luck!
Peter
Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012
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Good morning
i am beginner in c#, i can create form and other datagridviewer
but i am not able to connect my database witch hvae 17tables create in access2007 in c#.
i try to do but i have not get to do it.
please help me
i am trying to make a soft ware tour trade.
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How have you tried?
What code did you use?
Did you get any error messages, and if so, what where they, and where were they?
We need to know what you have done, as otherwise our answer could be miles away from the solution you need - and there are a lot of different ways you could have tried to do this and be having problems.
Remember that we can't see your screen, access your HDD, or read your mind!
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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You haven't given a lot to go on.
Can you actually make a connection?
Are you able to query the tables?
Is the displaying data an issue?
I would make sure your connection string is correct Access connection strings - ConnectionStrings.com[^]
also here is some MSDN example on connecting to an access database from C# ADO.NET Code Examples[^]
Every day, thousands of innocent plants are killed by vegetarians.
Help end the violence EAT BACON
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hello People,
Need your help in understanding .NET better. I know some basic stuff. problem is whenever I learn something new I dont remember it after few days. how can I implement these concepts so that I can memorize them better.
TIA
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Practice, practice, practice. It's the only way.
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Google is your friend. Reviewing old code for a technique or snippet is valuable. I stopped trying to memorize this crap years ago.
".45 ACP - because shooting twice is just silly" - JSOP, 2010
- You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
- When you pry the gun from my cold dead hands, be careful - the barrel will be very hot. - JSOP, 2013
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Get a book, and go through it cover to cover, doing all the exercises.
Then do them again.
After that, it's practice: there is no short cut - you remember best what you use, so if you don't use it you will lose it!
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
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OriginalGriff wrote: so if you don't use it you will lose it
so true, especially as you get older. Knowing that you have done a thing before and forgetting where you used it is endlessly frustrating.
Never underestimate the power of human stupidity
RAH
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my problem is different of style using css
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Then practice them over and over until you fully understand them. I find that attempting to explain things to others highlights the things I don't know as well as I thought I did.
This space for rent
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While the suggestions of practice are an important part, I think it's also important to understand foundations. If you know what a technique or pattern is meant to achieve, it will be a lot easier to hook it in memory.
By and large, various code languages really are just syntax for the same things. Yes, capabilities are different, but from where you're at it's much more important to understand the underlying principles. It's hard to learn the "how" when you don't understand the "why".
The most important thing I ever read for learning software engineering was Code: The Hidden Language of Computer Hardware and Software[^] by Charles Petzold. It's a great resource for getting those foundations.
It will help, I promise.
"There are three kinds of lies: lies, damned lies and statistics."
- Benjamin Disraeli
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Thank you people. your inputs mean alot to me. I guess now I know how to make programming interesting.
Thank you all for your help
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Dear friends,
I've developed an application which can convert text to speech.Now I want to control the speed of text spoken by computer i.e. customizing the speed of text. Please help how can I do this.
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Member 12297353 wrote: Please help how can I do this. Well, you could start off by telling us what you have used for your TTS solution. There are many different libraries that offer this and we would just be guessing what you have used.
This space for rent
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