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I'm programming with VB .NET 2010 and using a Microsoft Access Database file which is bound to my project as a Dataset. Now I want to know: BEFORE inserting a new row into my dataset table what will be the new ID number, or totally is it possible to know?
Surely you know the autonumber ID of a table is different with row count number, for there may be deleted rows between the table rows. Like the following example:
Row 0: ID=1
Row 1: ID=2
Row 2: ID=4 (ID number 3 is deleted)
Row 3: ID=5
Row 4: ID=9 (ID numbers 6,7,8 are deleted)
Now how do we know what ID number of Row 5 will be before inserting the new row? Perhaps ID numbers 10 and 11 are either deleted or not, so it may be 10, may be 11 or 12 or whatever! Is there a way to know it BEFORE adding or inserting the new row into the table?
Thank you beforehand.
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There is no way to know beforehand if you are using a standard identity value. If you need to know this beforehand, you are either going to have to generate the value yourself, or use something like a GUID instead - which you can assign in your code.
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One way is to store the last ID number in another table and increment it whenever a row is inserted into the table.
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Yes that's the best way, thanks for your remark.
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Hi Experts,
I am new with VS2008 and not able to find Event icon in Property window or anybody can tell me how i can view all events of particular control.
FYI..I am working with WPF.
Thanks,
Kidya
modified on Tuesday, August 30, 2011 3:31 AM
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At the top of the properties window you should see a tab with a yellow lightning bolt. Click on that and it should display all the available events for the highlighted control
"You get that on the big jobs."
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i am a beginner want to learn OOP in VB.Net.
In theory i understand OOP, but i do not understand apply in form of coding.
i need a sample application OOP, suppose the application inventory.Because i want to see how the use of OOP.
so, please help and teach me.
Thank you very much if you wanna help me..
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thank you very much.. i try first..
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How are you making out with this? Any specific questions?
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visualst wrote: so, please help and teach me.
I think you should pick up a book on OOPS with .Net and read it.
Too much of heaven can bring you underground
Heaven can always turn around
Too much of heaven, our life is all hell bound
Heaven, the kill that makes no sound
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hmm, i have a book. but i confuse in build a class like connection to databases.
but thank you for your advice.
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how to get and display values in listbox in vb.net
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One way to add values is to a add item by item.
E.g. listbox.Add("A");
You can add a range
E.g.
Dim s1 As String = "A"
Dim s2 As String = "B"
Dim s3 As String = "C"
listbox.Items.AddRange(New String() {s1, s2, s3})
A third way is to bind a collection to the listbox.
For this, you will use the DataSource and the DisplayMember property.
E.g.
listbox.DataSource = ds
listbox.DisplayMember = "ColumnName"
Too much of heaven can bring you underground
Heaven can always turn around
Too much of heaven, our life is all hell bound
Heaven, the kill that makes no sound
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Further to the previous post, you can also iterate the listbox items collection like;
For Each item As String in listbox1.Items
Debug.Writeline(item)
Next
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To expand on Dave's answer, remember that the items don't have to be strings (DataRows, for instance):
For Each item As String in listbox1.Items
Debug.Writeline(item)
Next
Could be
For Each item As DataRow in listbox1.Items
Next
Also, if you're looking for just the items that have been selected, replace
listbox1.Items with
listbox1.SelectedItems
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Hi again,
i'm looking at transaction management for EF. MSDN docs says that transaction are enforced only in the data source level ....so there's no direct way to manage transaction directly at object level as for example in Java?
Thanks
Ste
Ste
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Hi all,
I'm trying to understand where (and maybe if) there is a cache service for ADO.NET Entity framework.
I'm doing this just for a reasearch and comparison with JPA...
Java enforces two type of caches (one per entity context and one shared) but I do not find anything similar in .NET entity framework.
May anyone help me to deal with this problem?
Thanks
Ste
Ste
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AFAIK there is no caching provided. It is up the developer to implement since EF can be used in a variety of situations and what works for one may not be appropriate or necessary in another.
No comment
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So from this point of view (also academic point of view) Java Persistence API is better as is able to provide two different level cache where at least L1 cache does not provide any issues of concurrency, memory, and so on....
There're common widely used solution for 'manual' caching in ADO.NET EF can I check and mention?
I have just found this[^] on MSDN.
Thanks
Ste
Ste
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You are trying to compare oranges and coconuts. They both may grow on tree but they are vastly different in many ways.
You can't compare a .NET technology to a Java technology and determine one is "better" than the other. They each have their purpose and usage.
No comment
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I agree with you! but this is an academic assignment and I can't complain about this. Need to compare both appraches in term of: transparent mapping, caching, transactions, datastores, etc...
Ste
Ste
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Yes, then academically you can't conclude one is "better" than another. Present the facts.
Good luck
No comment
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