Hi all.

I used Hashtable to store data loaded from Access (the db can contain from
1000 till 100000 records), and that worked very well, because of fast data
retrieving from Hashtable using key.
The main problem with Hashtable is sorting. I have to convert all the
Hashtable to array list or smth, sort it with the help of ICompairer
interface, and then converting back to hashtable. That takes much time.
Now I am trying to modify the app code and started to use Datatable objects
instead of Hashtable. Datatable has a much faster sorting mechanism, and
that is very important for me, because I have to display the items from the
db in Listview - not all of them, just some (up to 50), but the items must
be ordered by certain key, t.i. the user should have possibility ti order
the items in the way he wishes. That's why fast sorting is neccessary.
ListView is in Virtual mode.
But on the other hand, datatable is not the one I am looking for. The item
retrieving from datatable (using datatable.rows.find (by key) is much slower
than getting items from hashtable. When for sorting and displaying, it is
not very bad, because, as I have said, I need at a moment dislpay only up to
50 items in Listview. But also my program has to make some calculations and
analysis with the data, so when it tries to retrieve data from datatable,
the speed of analyse decreases very markebly, in compairing to hashtable.

So, what could I do, if want to have fast sorting and also fast data
retrieving in my app? Storing the data both in datatable and in hashtable
could be a solution, but it consumes to much memory. Is there a class or
smth, that could provide this? Or should I try to write my own class
implementing many interfaces (for sorting etc.)?
I use VB.Net 2005.

It's get/set in VB as opposed to let/set in C#.

Andrius B. wrote:
Hi all.

I used Hashtable to store data loaded from Access (the db can contain
from
1000 till 100000 records), and that worked very well, because of fast
data
retrieving from Hashtable using key.
The main problem with Hashtable is sorting. I have to convert all the
Hashtable to array list or smth, sort it with the help of ICompairer
interface, and then converting back to hashtable. That takes much time.
Now I am trying to modify the app code and started to use Datatable
objects
instead of Hashtable. Datatable has a much faster sorting mechanism, and
that is very important for me, because I have to display the items from
the
db in Listview - not all of them, just some (up to 50), but the items
must
be ordered by certain key, t.i. the user should have possibility ti order
the items in the way he wishes. That's why fast sorting is neccessary.
ListView is in Virtual mode.
But on the other hand, datatable is not the one I am looking for. The
item
retrieving from datatable (using datatable.rows.find (by key) is much
slower
than getting items from hashtable. When for sorting and displaying, it is
not very bad, because, as I have said, I need at a moment dislpay only up
to
50 items in Listview. But also my program has to make some calculations
and
analysis with the data, so when it tries to retrieve data from datatable,
the speed of analyse decreases very markebly, in compairing to
hashtable.


Yes, a datatable is as slow as it gets and not very scalable.

http://msdn.microsoft.com/en-us/library/dd364983.aspx

copied
At the end of the day, however, if you’re using DataTables, the Select
method is one of the worst things you could possibly do to limit the
scalability of your application. We’ve discussed several alternatives
here, including LINQ, indexing tables to make use of Rows.Find, and
morphing the DataTable into a generic collection. Any of these options
will be orders of magnitude faster than Select for a set of records of
reasonable size. You also want to consider paring your set of records down
as much as possible to speed up both aggregation and selection of records.

end copy

So, what could I do, if want to have fast sorting and also fast data
retrieving in my app? Storing the data both in datatable and in hashtable
could be a solution, but it consumes to much memory. Is there a class or
smth, that could provide this? Or should I try to write my own class
implementing many interfaces (for sorting etc.)?
I use VB.Net 2005.

The example is in C# in the linq, but you can do the same in VB using
List<T>, a generic collection, which can be done VB2005.

http://dotnetslackers.com/Community/blogs/simoneb/archive/2007/06/20/How-to-sort-a-generic-List_3C00_T_3E00_.aspx

It's get/set in VB as opposed to let/set in C#.

http://www.java2s.com/Tutorial/VB/0120__Class-Module/PropertieswithGetterandSetter.htm

"Mr. Arnold" <Arnold at (no spam) Arnold.com> wrote in message
news:utnHehlVKHA.4704 at (no spam) TK2MSFTNGP06.phx.gbl...

It's get/set in VB as opposed to let/set in C#.

C# uses get/set.

-Scottt

Scott M. wrote:
"Mr. Arnold" <Arnold at (no spam) Arnold.com> wrote in message
news:utnHehlVKHA.4704 at (no spam) TK2MSFTNGP06.phx.gbl...

It's get/set in VB as opposed to let/set in C#.

C# uses get/set.

-Scottt


Besides, Let and Set is the same thing. VB6 uses Get and Let, but VB.NET
uses Get and Set.

By the way, I thing the binary search using IComparer interface (witch is
using for sorting such objects as Arraylist) is not the fastest one. Is
there
smth better? I mean, some kind of faster algorithm for sorting custom data
types?

Why not try a SortedList or a SortedDictionary? Just a thought!