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Pete O'Hanlon wrote: So, you have two checks in there - one to cope with the initial check, and a try/catch to cope with the database race condition.
I wouldn't do both if the exception handling is going to be necessary anyway. I see no advantage to doing that (e.g., performance would probably be better the exception route anyway). I sometimes see this strategy when dealing with multithreaded applications (e.g., you check a condition that is fast and commonly results in false, then you lock, then you check that condition again). However, I don't think that technique applies here, so I'd just go with the exception handling.
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The reason for the first is simply that you are giving the user information up front that the item already exists. The try/catch is for the really exceptional case where there's a race condition.
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I'd say that depends on the code/application. If the distinction between it being a race condition and it being an old duplicate key is unimportant, then I'd go with exception handling. If the race condition should be handled differently, then it makes sense to do both.
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Pete O'Hanlon wrote: there is no guarantee that this alone will work
10!
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Your problem is not how to deal with the error, the problem is what is the CAUSE of the error. There is no excuse for primary key violation and it is up to the developer to make sure the exception cannot arise in the normal flow of the program.
erdinc27 wrote: if the user tries to add an existing data it gives error like that
I suspect you are inserting instead of updating a record.
Never underestimate the power of human stupidity
RAH
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Mycroft Holmes wrote: There is no excuse for primary key violation
You're right in that - but the OP didn't have a primary key violation he had a unique constraint violation - which is legitimate.
For example, I am adding new products each of which has a unique id (maybe a GUID or an integer) which will be the primary key.
But the product also requires a human-readable Code - which is also required to be unique.
At some point the user needs to type in the code for a new product - you can check the DB at this point, and tell them to go ahead. Meanwhile another user can try to use the same code, pass the 'does it exist' test, and attempt a commit.
Whoever gets there first will be fine, the 2nd person's commit will fail.
___________________________________________
.\\axxx
(That's an 'M')
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_Maxxx_ wrote: he had a unique constraint violation
Ok I missed that mainly b/c I make no distinction between the 2 constraints, if that scenario existed then I would still do a select on the code field before inserting and feed the result back to the user. In the case of your new product I would return the record/info on the product entered by the first commit.
I admit there is a potential for a conflict on a really high volume system but I have yet to meet such a system.
Never underestimate the power of human stupidity
RAH
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Mycroft Holmes wrote: I admit there is a potential for a conflict on a really high volume system but I have yet to meet such a system.
Welcome to my world!
Imagine, if you will, something like a public facing web site that requires registration using a user name (rather than an email address which reduces but doesn't eliminate the problem).
___________________________________________
.\\axxx
(That's an 'M')
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I can just about see the latency issue getting into it there, I would think even that would need to be a fairly high volume system. Have you ever tracked the number of constraint violations?
I think I'll stick to my corporate systems and stay hidden behind the firewall thank you!
Never underestimate the power of human stupidity
RAH
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Catch it and interpret it -- which database engine?
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hey guys thanks for all your replies
i use MsSql 2008 express..and i tried something like that
try
{
dr[j] = xnl.Item(i).ChildNodes[j].InnerText;
}
catch(SqlException ex)
{
Console.WriteLine("This Record is already exist");
}
but still on the screen it shows the same error which is shown in Sql screen
and sometimes it gives error like object reference not set to an instance of an object in that line
dr[j] = xnl.Item(i).ChildNodes[j].InnerText;
what is wrong here.i read a Xml file over website and put it in a datatable is it because it cannot connect that site ?
vemedya.com
modified on Thursday, December 9, 2010 4:20 AM
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In this case, I'd suspect that xml.Item(i) doesn't have any child nodes, so attempting to do anything with it would cause a problem.
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I think exception try..catch.. can only save you from this trouble.
Just use Try and Catch SqlException.
And check the detail in SqlException,If it Contains word 'UNIQUE' then you'll get sure that the exception is regarding UNIQUE Key Constrain and further more you can notify to users with a formatted message.
That's not a big deal.
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Hiren Solanki wrote: ,If it Contains word 'UNIQUE'
And what do you do when you deploy it onto a localised version of SQL Server, say the Japanese version?
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Hi,
how to change (override) selected (highlighted)listviewitem background color in listview control.
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Subclass the control and handle the OnPaint method. Or use WPF and apply a template.
I know the language. I've read a book. - _Madmatt
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Guys,
I want to read PDF file in C# application.
Can anyone tell me what should i do?
Thanks,
Sunil G.
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You could use THIS[^] for complete information about parsing PDF file.
Underneath that page you will find one link which will redirect to our own Codeproject article and that is THIS[^].
Hope this will make you clear about your doubt regarding PDF parsing.
Regards,
Hiren.
Microsoft Dynamics CRM
"A SQL query goes into a bar, walks up to two tables and asks, "Can I join you?", "yes naturally""
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good links Hiren. 
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Dear Friends,
I need to add a customized DateTime picker control onto my webpage. As in my database table; the data is being stored in the following format:- "yyyy-mm-dd hh:mm:ss.mmm" so the user needs to select the date and time in the following format only in order to get the correct data from the database.
But I am not able to make such control. Could anyone help me out, how should i proceed with making this control?
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As far as I understand your question, You don't need to make such a custom control to display value in format you want. there's inbuilt property in DateTime Picker control of Custom format you can set custom format as you want accordingly.
See this MSDN[^] Article for more detail.
Regards,
Hiren.
Microsoft Dynamics CRM
"A SQL query goes into a bar, walks up to two tables and asks, "Can I join you?", "yes naturally""
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