Static function explained - C# Discussion Boards

Re: Custom Event Handler Problem.

Gareth H9-Feb-08 7:22

Gareth H

9-Feb-08 7:22

hdv212,

I think the problem is that MouseEventArgs is expecting a constructor that takes no params. So just add:

public MouseMoveExEventArgs()
{ }

Regards,
Gareth.

Re: Custom Event Handler Problem.

amargujrathi20069-Feb-08 8:06

amargujrathi2006

9-Feb-08 8:06

If you want to add new constructor in derived class, there should be exact match of constructor in base class with same parameter. If not then there you have to make call of base class constructor explicitly .

So here i have made call to base constructor as following arguments,
you can change it.

public MouseMoveExEventArgs(Point mapScrollPosition)
: base(MouseButtons.Left, 1, mapScrollPosition.X, mapScrollPosition.Y, 2)

Hope it will helpful

Regards
Amar

Re: Custom Event Handler Problem.

hdv2129-Feb-08 8:10

hdv212

9-Feb-08 8:10

thanks
does you know an helpful article about Custome Event Handler ?
thanks

GPS Data String

Simerjots9-Feb-08 5:29

Simerjots

9-Feb-08 5:29

Hey Guys,

What is the most effcient way to get data of this string?

$GPGGA,040144.21,,,,,00,02,5.0,,M,-0.582109,M,0.00701,*4B??$GPRMC,040144.21,V,,,,,,,090208,,*1A??$GPGSA,A,1,30,31,,,,,,,,,,,05,05,05*1A??$GPGGA,040145.14,,,,,00,03,5.0,,M,-0.582100,M,0.00701,*44??$GPRMC,040145.14,V,,,,,,,090208,,*1D??$GPGSA,A,1,01,30,31,,,,,,,,,,05,05,05*1B??$GPGGA,040146.23,,,,,00,03,5.0,,M,-0.582100,M,0.00701,*43??$GPRMC,040146.23,V,,,,,,,090208,,*1A??$GPGSA,A,1,01,30,31,,,,,,,,,,05,05,05*1B??$GPGGA,040147.18,,,,,00,03,5.0,,M,-0.582110,M,0.00701,*4B??$GPRMC,040147.18,V,,,,,,,090208,,*13??$GPGSA,A,1,01,30,31,,,,,,,,,,05,05,05*1B??$GPGGA,040148.20,,,,,00,03,5.0,,M,-0.582110,M,0.00701,*4F??$GPRMC,040148.20,V,,,,,,,090208,,*17??$GPGSV,3,1,12,31,75,336,29,01,75,058,26,14,48,104,,30,35,050,25*74??$GPGSV,3,2,12,20,25,310,,16,22,013,,05,18,044,,29,16,013,*7B??$GPGSV,3,3,12,06,15,118,,22,13,166,,12,06,038,,23,04,303,*78??$GPGSA,A,1,01,30,31,,,,,,,,,,05,05,05*1B??$GPGGA,040149.21,,,,,00,03,5.0,,M,-0.582110,M,0.00701,*4F??$GPRMC,040149.21,V,,,,,,,090208,,*17??$GPGSA,A,1,01,30,31,,,,,,,,,,05,05,05*1B??$GPGGA,040150.22,,,,,00,03,5.0,,M,-0.582110,M,0.00701,*44??$GPRMC,040150.22,V,,,,,,,090208,,*1C??$GPGSA,A,1,01,30,31,,,,,,,,,,05,05,05*1B??$GPGGA,040151.22,,,,,00,03,5.0,,M,-0.582110,M,0.00701,*45??$GPRMC,040151.22,V,,,,,,,090208,,*1D??$GPGSA,A,1,01,30,31,,,,,,,,,,05,05,05*1B??$GPGGA,040152.21,,,,,00,00,5.0,,M,-0.509010,M,0.00701,*44??$GPRMC,040152.21,V,,,,,,,090208,,*1D??$GPGSA,A,1,,,,,,,,,,,,,05,05,05*1B??$GPGGA,040153.15,,,,,00,01,5.0,,M,-0.509010,M,0.00701,*43??$GPRMC,040153.15,V,,,,,,,090208,,*1B??$GPGSV,3,1,12,31,75,336,27,01,75,058,,14,48,104,,30,35,050,*79??$GPGSV,3,2,12,20,25,310,,16,22,042,,05,18,044,,29,16,042,*7B??$GPGSV,3,3,12,06,15,118,,22,13,166,,12,06,038,,23,04,303,*78??$GPGSA,A,1,31,,,,,,,,,,,,05,05,05*19??$GPGGA,040154.21,,,,,00,01,5.0,,M,-0.509010,M,0.00701,*43??$GPRMC,040154.21,V,,,,,,,090208,,*1B??$GPGSA,A,1,31,,,,,,,,,,,,05,05,05*19??$GPGGA,040155.18,,,,,00,01,5.0,,M,-0.509010,M,0.00701,*48??$GPRMC,040155.18,V,,,,,,,090208,,*10??$GPGSA,A,1,31,,,,,,,,,,,,05,05,05*19??$GPGGA,040156.14,,,,,00,02,5.0,,M,-0.509010,M,0.00701,*44??$GPRMC,040156.14,V,,,,,,,090208,,*1F??$GPGSA,A,1,06,31,,,,,,,,,,,05,05,05*1F??$GPGGA,040157.16,,,,,00,03,5.0,,M,-0.509014,M,0.00701,*42??$GPRMC,040157.16,V,,,,,,,090208,,*1C??$GPGSA,A,1,06,30,31,,,,,,,,,,05,05,05*1C??$GPGGA,040158.19,,,,,00,03,5.0,,M,-0.509014,M,0.00701,*42??$GPRMC,040158.19,V,,,,,,,090208,,*1C??$GPGSV,3,1,12,31,75,336,27,01,75,058,,14,48,104,,30,35,050,18*70??$GPGSV,3,2,12,20,25,310,,16,22,073,,05,18,044,,29,16,073,*7B??$GPGSV,3,3,12,06,15,118,22,22,13,166,,12,06,038,,23,04,303,*78??$GPGSA,A,1,06,30,31,,,,,,,,,,05,05,05*1C??$GPGGA,040159.21,,,,,00,03,5.0,,M,-0.509014,M,0.00701,*48??$GPRMC,040159.21,V,,,,,,,090208,,*16??$GPGSA,A,1,06,30,31,,,,,,,,,,05,05,05*1C

Re: GPS Data String

pmarfleet9-Feb-08 7:20

pmarfleet

9-Feb-08 7:20

Use a regular expression to split each line of text into its constituent parts. Regular expression support is provided by the Framework in the System.Text.RegularExpressions namespace.

See the following link[^] for more information on regular expression syntax in .NET.

Paul Marfleet

"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush

Re: GPS Data String

Ed.Poore9-Feb-08 10:25

Ed.Poore

9-Feb-08 10:25

pmarfleet suggested using Regular Expressions. Depending on the speed of the data coming in etc it might be suitable. However read through:
http://www.codeproject.com/KB/vb/WritingGPSApplications1.aspx[^]

Basically you can do some error checking, or the fastest way to split up the data into the various strings would probably be:

string[] individualStrings = sourceString.Split('$');
foreach (string individual in individualStrings)
{
    string[] parameters = individual.Split(',');
    // Now you have all the parameters split up into an array.
}

Re: GPS Data String

Mark Churchill9-Feb-08 14:34

Mark Churchill

9-Feb-08 14:34

Theres a freeware library around that pulls these strings apart and gives you the data nicely labelled. Google some more Wink | ;)

Mark Churchill
Director
Dunn & Churchill
Free Download:
Diamond Binding: The simple, powerful, reliable, and effective data layer toolkit for Visual Studio.

Static function explained

steve_rm9-Feb-08 2:38

steve_rm

9-Feb-08 2:38

Hello,

I am just writing simple threading program in C# program, I am coming from VB.Net and just wondering why my WriteY() function has to be a static. I through this could be public or private.

Can anyone explain why it has to be a static.

Many thanks,

Steve

<br />
using System;<br />
using System.Collections.Generic;<br />
using System.Text;<br />
using System.Threading;<br />
<br />
namespace App1<br />
{<br />
    class Program<br />
    {<br />
        static void Main(string[] args)<br />
        {<br />
            Thread t = new Thread(WriteY);<br />
            t.Start();<br />
            while (true) Console.Write("X");<br />
        }<br />
<br />
        static void WriteY()<br />
        {<br />
            while (true)<br />
                Console.Write("Y");<br />
        }<br />
    }<br />
}<br />

Re: Static function explained

Not Active9-Feb-08 2:42

Not Active

9-Feb-08 2:42

You are calling the method from within a static method, Main.

http://www.cis.upenn.edu/~matuszek/cit591-2006/Pages/static-vs-instance.html[^]

only two letters away from being an asset

Re: Static function explained

DeveshKumar9-Feb-08 5:10

DeveshKumar

9-Feb-08 5:10

www.csharphelp.com/archives/archive148.html

Re: Static function explained

Pete O'Hanlon9-Feb-08 9:29

Pete O'Hanlon

9-Feb-08 9:29

WriteY is static because you are calling it from the Main method without creating an instance of the Program class in the Main method.

Deja View - the feeling that you've seen this post before.

My blog | My articles

Linq query vs foreach loop [modified]

DaveyM699-Feb-08 1:13

DaveyM69

9-Feb-08 1:13

I'm loving the Linq stuff, it's very cool and flexible, but I don't want to use is for the sake of it.

I currently have a Generic List of DVD objects that have Name and ID properties.
I'm writing a simple method in the List to return the Name of the DVD given an ID and return an empty string if it's not found.

Before I was doing

public string GetName(int ID)
{
    foreach (DVD thisDVD in this)
    {
        if (thisDVD.ID == ID)
        { return thisDVD.Name; }
    }
    return "";
}

which works fine, but after playing with Linq, I found myself writing

public string GetName(int ID)
{
    var idQuery =
        from dvd in this
        where dvd.ID == ID
        select dvd.Name;
    foreach (string name in idQuery)
    { return name; }
    return "";
}

which works fine too.

I was wondering which to use? I figured that the first one was better, as in the second Linq is iterating over the collection and then I have to iterate over the results. Surely only one trip over and breaking out if/when the required result is found is better? Is there something in the framework that makes Linq more efficient?

Dave

modified on Saturday, February 9, 2008 7:25 AM

Re: Linq query vs foreach loop

^That's Aragon9-Feb-08 1:30

^That's Aragon

9-Feb-08 1:30

Hi Dave!

Look here[^]

Regards.

"Save water,It's precious" Smile | :)

"Don't forget to vote" Wink | ;)

Re: Linq query vs foreach loop

Daniel Grunwald9-Feb-08 2:27

Daniel Grunwald

9-Feb-08 2:27

LINQ is a bit slower due to the overhead of tons of method calls (there are lots of calls to MoveNext() and the closure). The current JIT is not able to optimize this, but it's possible to write an IL-level optimizer that inlines all LINQ method calls, then inlines the closure method calls and removes the closure objects, converting the fields representing captured variables back into local variables.
I've written a prototype optimizer that can remove the closure in code like this:

static List<int> someIntList = new List<int>();

static bool ExistsTest(int divisor)
{
	return Exists(someIntList, i => i % divisor == 0);
}

static bool Exists(IEnumerable<int> input, Predicate<int> pred)
{
	if (pred == null) {
		throw new ArgumentNullException("pred");
	}
	foreach (int i in input) {
		if (pred(i))
			return true;
	}
	return false;
}</int></int></int></int>

What's missing until it gets useful is cross-assembly inlining and support for generic methods.

Re: Linq query vs foreach loop

DaveyM699-Feb-08 3:04

DaveyM69

9-Feb-08 3:04

Thanks cosmo - that's been very helpful

Dave

Re: Linq query vs foreach loop

Gareth H9-Feb-08 1:31

Gareth H

9-Feb-08 1:31

DaveyM69,

Since your using a List<t> why not do:

return list[list.IndexOf(ID)];

And you could always add list.Containts(ID) before the above to check its in the list so you dont get an exception. It just seems simpler/quicker than iterating.

Regards,
Gareth.

Re: Linq query vs foreach loop

Daniel Grunwald9-Feb-08 2:36

Daniel Grunwald

9-Feb-08 2:36

I would write it this way:

public string GetName(int ID)
{
    return
       (from dvd in this
        where dvd.ID == ID
        select dvd.Name
       ).FirstOrDefault() ?? "";
}

If performance of GetName is an issue, neither a loop nor LINQ is efficient; you should use a Dictionary ID->dvd.

Re: Linq query vs foreach loop

DaveyM699-Feb-08 3:03

DaveyM69

9-Feb-08 3:03

Daniel Grunwald wrote:
FirstOrDefault()

I was just looking at the Element Operations on MSDN Smile | :)

I've tried various ways of coding it and Linq is definately slower in ALL situations (it is more 'elegant' though) by between 30 and 50%.

Performance isn't really an issue in this app but I didn't want to deliberately add overhead.

Thanks for all your help and suggestions everyone!

Dave

Re: Linq query vs foreach loop

WillemM9-Feb-08 7:54

WillemM

9-Feb-08 7:54

One of the reasons that you would use LINQ is that it allows you to write simpler code.
You query for the DVD could be a lot shorter.

public string GetName(int ID)
{
return this.Where(d => d.ID == id).Select(d => d.Name).FirstOrDefault() ?? String.Empty;
}

This is acually quite efficient, as the linq operator doesn't copy any data, but uses chained yield return methods to find the required subset of dvd's. So Link is actually just as efficient as your code would be, with the added advantage of a simple query language.

WM.

What about weapons of mass-construction?
"What? Its an Apple MacBook Pro. They are sexy!" - Paul Watson
My blog

Re: Linq query vs foreach loop

DaveyM699-Feb-08 8:29

DaveyM69

9-Feb-08 8:29

I've just tested it on one million records searching for the id 999999 and it still performs about 30 to 50% slower than a foreach loop.

It seems that regardless of what you atually try to do with a Linq query it calls some sort of internal ToArray() method (so the result supports the IEnumerable interface I assume) and that's where the performance is lost.

For complex queries I think Linq has some huge advantages, but for simple ones it seems the old foreach is better.

Dave

Re: Linq query vs foreach loop

Guffa9-Feb-08 8:30

Guffa

9-Feb-08 8:30

Why not simpy:

public string GetName(int ID) {
   DVD found = this.Find(d => d.ID == ID);
   return found != null ? found.Name : string.Empty;
}

But, as Daniel said, if performance is an issue, you should use a dictionary instead of a list.

Experience is the sum of all the mistakes you have done.

Re: Linq query vs foreach loop

DaveyM699-Feb-08 8:44

DaveyM69

9-Feb-08 8:44

The dictionary would be fine if a 'real world' class were actually as simple as the example. If matching multiple properties then it's not much use.

That code performs 10 to 20% quicker than a foreach! Cool, thankyou! Big Grin | :-D

Dave

Re: Linq query vs foreach loop

Guffa9-Feb-08 11:40

Guffa

9-Feb-08 11:40

DaveyM69 wrote:
f matching multiple properties then it's not much use.

Then just make a key that contains multiple properties. Make a class that implements IEqualityComparer and use that as comparer when you create the dictionary.

DaveyM69 wrote:
That code performs 10 to 20% quicker than a foreach!

Hm... that's pretty strange, as all the Find method does is looping through the items and calling the delegate...

A dictionary would perform about 100000% faster...

Experience is the sum of all the mistakes you have done.

Re: Linq query vs foreach loop

Guffa13-Feb-08 8:19

Guffa

13-Feb-08 8:19

DaveyM69 wrote:
If matching multiple properties then it's not much use.

Regarding that, I wrote an article about how to make a custom key for a dictionary:

Dictionary with a custom key[^]

Experience is the sum of all the mistakes you have done.

Document scanning in C#

Member 26713148-Feb-08 23:27

Member 2671314

8-Feb-08 23:27

Hi,Please tel me how I can scan a document in c#.thanks.

Chamanara Shapoor

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.