Solved

for each where

Posted on 2010-09-03
7
341 Views
Last Modified: 2012-05-10
Is there a way in vb.net select all elements from a for each statement using a where?
I am not a fan of linq for speed purposes.
It is for a game type program so speed is critical.


I want to iterate through only some  elements of a list . Those elements meet some condition.
Like  iterate through a list of objects where some property is set to false.

I can use a for each and and if statement currently but I am after a better way.


  For Each pt In Mpl
            If pt.direction = missileType Then
...
0
Comment
Question by:jagguy
7 Comments
 
LVL 47

Expert Comment

by:Wayne Taylor (webtubbs)
ID: 33601628
The only way to do that is with LINQ.    Dim pts = From pt In Mpl Where pt.Direction = missleType    For Each pt In pts        ''''    NextWayne
0
 
LVL 85

Expert Comment

by:Mike Tomlinson
ID: 33601700
You can use the List.FindAll() method:
http://msdn.microsoft.com/en-us/library/fh1w7y8z.aspx

Really not sure if it is "better" though...just different...

Made up example:
Public Class Form1

    Private Const missileType As Integer = 0

    Private Class Something
        Public direction As Integer
    End Class

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim Mpl As New List(Of Something)

        ' ...

        For Each pt In Mpl.FindAll(AddressOf FindMissiles)
            ' ...
        Next
    End Sub

    Private Function FindMissiles(ByVal pt As Something) As Boolean
        Return pt.direction = missileType
        ' ... obviously a more complicted match algorithm could be used in here! ...
    End Function

End Class

Open in new window

0
 
LVL 51

Expert Comment

by:Huseyin KAHRAMAN
ID: 33601754
what about creating a dynamic datatable, put elements into it (maybe you already getting values from db, in this case you may have a datatable already)
then you can use rowfilter property of datatable.defaultview.rowfilter="id > 10 and id < 20"

--> http://msdn.microsoft.com/en-us/library/system.data.dataview.rowfilter.aspx
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 

Author Comment

by:jagguy
ID: 33601903
thanks for the replies.

actually it looks worse with all these  extra functions and I am wooried about speed as well, database no way and MSDN examples dont always clarify things. Who wites MSDN stuff and does it get proof read for simplicity?
0
 
LVL 8

Expert Comment

by:Gururaj Badam
ID: 33602163
I'm a C# guy, pardon my syntax.

For Each pt In Mpl.Where pt => pt.direction = missileType


this will only iterate elements matching your where condition. I don't know why you feel LINQ will slow down your processing when it's actually design gain performance.
0
 

Author Comment

by:jagguy
ID: 33605978
i havent read anywhere Liunq speeds up performance and have only heard it slows things down because of its design.

Could you show me any article where it says iterating through a list of data using linq is quicker ( or no slwere)than using an if condition .
0
 
LVL 8

Accepted Solution

by:
Gururaj Badam earned 500 total points
ID: 33606127
@jagguy - I couldn't believe until i did a test. You're right.
0

Featured Post

Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Regarding swagger API 1 32
ASP.NET - Why is accordion not working? 3 45
Set custom font WPF 2 21
Converting PHP triple des decrypt to c# 9 62
More often than not, we developers are confronted with a need: a need to make some kind of magic happen via code. Whether it is for a client, for the boss, or for our own personal projects, the need must be satisfied. Most of the time, the Framework…
The ECB site provides FX rates for major currencies since its inception in 1999 in the form of an XML feed. The files have the following format (reducted for brevity) (CODE) There are three files available HERE (http://www.ecb.europa.eu/stats/exch…
Although Jacob Bernoulli (1654-1705) has been credited as the creator of "Binomial Distribution Table", Gottfried Leibniz (1646-1716) did his dissertation on the subject in 1666; Leibniz you may recall is the co-inventor of "Calculus" and beat Isaac…

713 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question