C# Discussion Boards - CodeProject

Guffa10-Oct-08 12:26

Guffa

10-Oct-08 12:26

The only strict requirement for the GetHashCode method is that it should always return the same hash code for a given value. So, this is a valid implementation of the method:

public override int GetHashCode() {
   return 0;
}

However, that gives bad performance when you use the hash code for example in a dictionary. For good performance, the hash codes should be evenly distributed over the Int32 range of values.

This is how the implementation looks for the Int32 type:

public override int GetHashCode() {
   return this;
}

This is how the implementation looks for the Int64 type:

public override int GetHashCode() {
   return ((int)this) ^ ((int)(this >> 0x20));
}

As you see, it just throws away the top 12 bits. If you want to use all the bits in the hash code, you can just do an xor of the upper and lower value:

public override int GetHashCode() {
   return m_Upper ^ m_Lower;
}

Despite everything, the person most likely to be fooling you next is yourself.

DaveyM6910-Oct-08 12:54

DaveyM69

10-Oct-08 12:54

Thanks Guffa Big Grin | :-D

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)

DaveyM6910-Oct-08 13:05

DaveyM69

10-Oct-08 13:05

Guffa wrote:
throws away the top 12 bits

Actually, it's just splitting it into 2 ints and xoring them - 0x20 (Hex!) Wink | ;)

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)

Re: Finding in datagridview

Guffa10-Oct-08 14:09

Guffa

10-Oct-08 14:09

Yes, you are right. Why didn't I think of that, that is what I would expect it to do... Smile | :)

Despite everything, the person most likely to be fooling you next is yourself.

Finding in datagridview

ArielR10-Oct-08 11:43

ArielR

10-Oct-08 11:43

Which is the elemental code for searching in a datagridview column?. How to give the focus at the row with the value found?

Pedram Behroozi10-Oct-08 12:21

Pedram Behroozi

10-Oct-08 12:21

Not sure what you're trying to do but you don't need to search into Columns, you can simply search in Rows:

DataGridView dgv = new DataGridView();
DataGridViewRow dgvr = new DataGridViewRow();
dgvr.Cells[0].Value = "Hello!"; // Or anyting that you want to search (not only Strings, not only Zero)

dgv.Rows[dgv.Rows.IndexOf(dgvr)].Selected = true;

While (true) { Human.isLearnable = true; }

Re: Finding in datagridview

nelsonpaixao10-Oct-08 12:38

nelsonpaixao

10-Oct-08 12:38

You can do that with sql procedures, after trigger it in a c# event WTF | :WTF:

nelsonpaixao@yahoo.com.br

trying to help & get help

Re: Finding in datagridview

Wendelius10-Oct-08 22:01

Wendelius

10-Oct-08 22:01

AFAIK the searching should be implemented at data source level. If you're using BindingSource as datasource, have a look at BindingSource.Find Method (String, Object)[^]

The need to optimize rises from a bad design

form_load and performclick()

Saamir10-Oct-08 10:46

10-Oct-08 10:46

Hi guys,
Need some help please. I have a scan feature in my form and on form_load I am trying to fire the btnScan.performclick() event. It works but my form doesn't load until scanner times out or then I scan. I want the form to load and the picturebox to show no image while the scanner is waiting for an image.

I hope I am making sense.

Sameer

Sameer

vineas10-Oct-08 11:03

vineas

10-Oct-08 11:03

Have a timer that gets started in the form load event, and then do the btnScan.PerformClick() in the timer's event handler.

-----
In the land of the blind, the one eyed man is king.

Saamir13-Oct-08 4:43

13-Oct-08 4:43

Thank you for your suggestion, it worked... Smile | :)

Sameer

Pedram Behroozi10-Oct-08 11:04

Pedram Behroozi

10-Oct-08 11:04

I think you need Threading[^]

While (true) { Human.isLearnable = true; }

Saamir10-Oct-08 11:06

10-Oct-08 11:06

can you please give me an example

Thanks

Sameer

Pedram Behroozi10-Oct-08 11:12

Pedram Behroozi

10-Oct-08 11:12

Sure[^]

While (true) { Human.isLearnable = true; }

DaveyM6910-Oct-08 11:26

DaveyM69

10-Oct-08 11:26

For simplicity - use the BackgroundWorker component.

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)

Saamir13-Oct-08 4:44

13-Oct-08 4:44

Thank you Davey,
I decided to go with a timer that calls the performclick event. Thanks

S

Sameer

Dave Kreskowiak10-Oct-08 11:29

Dave Kreskowiak

10-Oct-08 11:29

You don't put all the code for doing the scan in the btnScan.Click event handler. You put it in it's own method somewhere, then you can call that method from anywhere in your code, including the btnScan.Click event handler AND from in your Load event.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007, 2008

Saamir13-Oct-08 4:42

13-Oct-08 4:42

Thank you Dave for your response. I tried your suggestion and it didn't work, I believe the problem is that I have a while loop that waits for a response from the scanner in my btnscan_click event.

I instead added a timer and I am calling the btnScan.Performclick from there. That seems to be working, I am not sure if this is the best way to go with it but it works Smile | :)

Sameer

layered graphics

MarcosDiFazio10-Oct-08 9:42

MarcosDiFazio

10-Oct-08 9:42

hi,
I work in an application to show figures. I want diferent layers to each figue. I need draw figures independently one to another.
I´m using a transparent bitmap for each figure, and in OnPaint of a panel i draw all. But i got flicker when i move the objets.
What tecnics or class i could use to acomplish mi goals.
Thanks

Marcos.

MarkB77710-Oct-08 12:43

MarkB777

10-Oct-08 12:43

Using DirectX would be a better approach. Have a look into 2D imaging in XNA.

Cheers,

Mark Brock
"We're definitely not going to make a G or a PG version of this. It's not PillowfightCraft." -- Chris Metzen
Click here to view my blog

MarcosDiFazio11-Oct-08 1:02

MarcosDiFazio

11-Oct-08 1:02

Thanks Mark, Im investigating directx now.

Thomas Stockwell10-Oct-08 12:44

Thomas Stockwell

10-Oct-08 12:44

You need to make sure that no graphic manipulation is being done by any other method except the OnPaint method. The graphical and logical aspects of user controls must be independent for a smoot and flicker free control.

One of my articles has been able to help quite a few people with custom paint routines: Basics of Falling Blocks in VB 2005[^]

Regards,
Thomas Stockwell

Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning.

Visit my Blog

MarcosDiFazio11-Oct-08 1:08

MarcosDiFazio

11-Oct-08 1:08

hi Thomas.
I read your article. I have problems with graphics. the quid of question is what tool i must to use to implement layered grapchics?. Then each figure must respond to mouse events, and have their own properties.
regards
Marcos

Thomas Stockwell11-Oct-08 2:27

Thomas Stockwell

11-Oct-08 2:27

Well, basically you could have a collection of the layered objects. The layered object would hold important points, color information, and size information. Then the OnPaint method would have iterate through each of those objects and reproduce the graphics based on the information from the collection.
For mouse events, just find out which graphic is underneath the mouse when it is clicked. Then iterate through the collection until you find a graphic with the specified point. Then manipulate the objects point information.