C# Discussion Boards - CodeProject

Re: How do I Clear the contents of my Datagridview

Quinton2-Apr-08 2:15

2-Apr-08 2:15

Luc Pattyn wrote:
Hi,

IMO there are two ways:
- when bound to a datasource, clear the datasource
- or clear the binding, then do Rows.Clear()

Luc Pattyn [Forum Guidelines] [My Articles]

Thanks Luc! After clearing the datasource I then used the Rows.Clear(0) : and it works 100% Big Grin | :-D

Math Equations

nike_arh1-Apr-08 23:56

nike_arh

1-Apr-08 23:56

Hi, i have a math question. Can i find the roots of inequalities in C# - is there any algorithm. For example the equation is
x^4 + 3*x^2 + 8 > 0 or sin(2*x) + cos(3*x) < 1
...
How can i find with a program the roots of these inequalities?
I need to know this because i am writing a program which draws math graphs. It can draw inequalities (for example sin(2*x) < cos(x) ) and mark the intervals at which inequality has roots (where sine is smaller than cosine from the example). The hard part is that i can't find the points where the inequalities intersect - i can't find the bounds of the intervals where the solutions are.

Still learning...

Re: Math Equations

Luc Pattyn2-Apr-08 0:07

Luc Pattyn

2-Apr-08 0:07

Hi,

you can solve a small fraction of all possible equations analytically; e.g. your first
example is a quadratic equation, where x^2 is the unknown. Since the discriminant is
negative, it will have four complex solutions, no real ones.
Your second example can be transformed into a pair of equations in s and c, where
s=sin(x) and c=cos(x), the second equation being s*s + c*c = 1

For plotting purposes you don't really need an analytic solution; you can just somehow
define the range that interests you, and calculate the function for several values inside
that range.

And you can always try and solve an equation of the form f(x)=0 by an iterative
approach, see e.g. Newton-Raphson algorithm.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

This month's tips:
- before you ask a question here, search CodeProject, then Google;
- the quality and detail of your question reflects on the effectiveness of the help you are likely to get;
- use PRE tags to preserve formatting when showing multi-line code snippets.

Re: Math Equations

Russell Jones2-Apr-08 0:39

Russell Jones

2-Apr-08 0:39

you could try using the api for something like matlab, but I suspect MatLab is very expensive, I've only every used a copy in a university computing lab.

Otherwise You'll need to write code to solve general cases of each equation or an algebra module to rearrange the equations into a general case.

As Luc has already said something like Newton Raphson might be a good idea but you need to have a rough idea of where the roots are inorder to find all of them

HTH

Russell

windows application code(exporting datatable to .csv format)

sharanabasava1-Apr-08 23:46

sharanabasava

1-Apr-08 23:46

Clicking on the Export button will show a window in which to set the name of the exporting file. The Field delimiter will also need to be specified (the column separator character) and you will also be able to specify whether First row contains field names. Finally, you’ll be able to select the fields to be exported and, after clicking on the Next button, exporting process will start.

Re: windows application code(exporting datatable to .csv format)

Giorgi Dalakishvili1-Apr-08 23:53

Giorgi Dalakishvili

1-Apr-08 23:53

Smells like an assignment. Anyway, Google is your friend as well as codeproject.

Giorgi Dalakishvili

#region signature
my articles
#endregion

How to change animation in waitcursor in compact framework?

scoroop1-Apr-08 23:26

scoroop

1-Apr-08 23:26

Hi, my whole question is in the subject... In regular desktop framework i can just construct my own cursor. but when working with CF i noticed that it's impossible, because no constructor is exposed. Nonetheless there are programs which can do this. How? I have no clue. Perhaps you can help me Smile | :)

thanks guys

How can i add tab bar using VS 2008 in WPF Application?

bankey10101-Apr-08 23:17

bankey1010

1-Apr-08 23:17

Hi All,

I am new with VS 2008 and WPF application. so i am making a WPF Application but now i have to add "tab bar" like office 2007 instead of menues.

can anyone please tell me how to add tab bar on main window of WPF application.

Thanks
Bankey

Re: How can i add tab bar using VS 2008 in WPF Application?

Simon P Stevens2-Apr-08 1:53

Simon P Stevens

2-Apr-08 1:53

The "tab bar" you speak of is officially called a "Ribbon"

There's no built in Ribbon control in Vs2008. There are several 3rd party control vendors that offer Ribbon UI controls, and a few of them have WPF versions.

At least two I can think of are
http://www.devcomponents.com/[^]
and
http://www.infragistics.com[^]

I've seen free versions around as well at various stages of completeness, just google it.

You should be aware that you have to sign an IP agreement with Microsoft to implement the Ribbon bar in your application:
http://www.microsoft.com/presspass/features/2006/nov06/11-21officeui.mspx[^]
http://msdn2.microsoft.com/en-us/office/aa973809.aspx[^]

Simon

How to call a c++ function from c# program

sree1-Apr-08 23:14

sree

1-Apr-08 23:14

Hi,

Can anyone of you, tell me how to call c++ functions from c# program?

I have a C++ dll, in which i have some functions, now i want to call them from my c# code. Please tell me how can i do this. If possible provide me sample code n all.

Thank you in advance

Bye,
sree

sree

Re: How to call a c++ function from c# program

N a v a n e e t h1-Apr-08 23:19

N a v a n e e t h

1-Apr-08 23:19

You need to write a wrapper for C++ dll in C#. Use DllImport[^] attribute.

All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia

How to use google | Ask smart questions

Re: How to call a c++ function from c# program

sree1-Apr-08 23:33

sree

1-Apr-08 23:33

Hi Navaneeth,

I have tried it, but i ended with an exception " unable to find an entry point named function-name in dll".Can u provide some more detailed information regarding this.

sree

Re: How to call a c++ function from c# program

Jonathan [Darka]2-Apr-08 0:19

Jonathan [Darka]

2-Apr-08 0:19

The C++ function name will be mangled, see here[^].

Alternatively you could wrap the DLL in a inprocess COM object and use COM Interop to use it.

If you want to avoid issues with the Name Mangling (which is non-standard accross compilers) then you need to write a C DLL, rather than a C one.

regards,

Jonathan Wilkes
Darka[Xanya.net]

WTF??? AccessViolationException Issue

Harvey Saayman1-Apr-08 22:12

Harvey Saayman

1-Apr-08 22:12

Hey Guys,

I just got the scariest Exception I've ever seen!

It reads... AccessViolationException Was Unhanded, Attempted To Read Or Write Protected Memory. This is often an indication that other memory is corrupt.

In Visual Studio It points out Application.Run(new frmMain()); As the culprit

I have no idea why this happens, it seems random because i call only one method and it works most of the time. Even when i do get the Exception the program got around to logging data in my database (thhis is the 2nd last step of the process I'm coding) So im thinking it might be where i call These methods...

cmd.Dispose(); //sql command
newSqlConn.Close(); //sql connection
newSqlConn.Dispose();

But i might be wrong, i still need a way to replicate the damn error so that i can step though the code and see exactly where it breaks.

So my question is this, have any of you ever come across this error? Why does it happen and where do u think i should start looking to fix it?

thanx

Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS

you.suck = (you.passion != Programming)

Re: WTF??? AccessViolationException Issue

phannon⁸⁶1-Apr-08 22:24

phannon⁸⁶

1-Apr-08 22:24

I've come across it when painting to picture boxes containing a bitmap. I was attempting to write colour to a segment of the box but I forgot to convert the bmp back from monochrome after some processing I did, also attempting to point at a segment outside of the bounds of the bmp caused this (but that was more obvious to spot). Other than that, I haven't come across it before.

He who makes a beast out of himself gets rid of the pain of being a man

Re: WTF??? AccessViolationException Issue

Harvey Saayman1-Apr-08 22:29

Harvey Saayman

1-Apr-08 22:29

i do no painting in this particular program...

im getting data from an external device and writing it to my database, the weird thing is that it works most of the time. i wish it gave me more info on whats going wrong...

Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS

you.suck = (you.passion != Programming)

Re: WTF??? AccessViolationException Issue

phannon⁸⁶1-Apr-08 22:38

phannon⁸⁶

1-Apr-08 22:38

Unfortunately I can't help then, that's the extent of my experience with this exception, hopefully someone else will be along shortly to help you out Smile | :)

He who makes a beast out of himself gets rid of the pain of being a man

Re: WTF??? AccessViolationException Issue

Harvey Saayman1-Apr-08 22:47

Harvey Saayman

1-Apr-08 22:47

i hope so too,

thanx tho

Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS

you.suck = (you.passion != Programming)

Re: WTF??? AccessViolationException Issue

Rob Philpott1-Apr-08 22:39

Rob Philpott

1-Apr-08 22:39

Exceptions often get thrown in Application.Run. I *think* its just the exception bubbling up to the top level handler. You could try putting methods further up the call stack in exception blocks and make sure you've got first chance exception throwing switched on in the debugger to narrow it down a bit.

You must be using some sort of interop or 3rd party component no?

Regards,
Rob Philpott.

Re: WTF??? AccessViolationException Issue

Harvey Saayman1-Apr-08 22:45

Harvey Saayman

1-Apr-08 22:45

i am, im using an SDK provided by the manufacturer of the external device im getting data from. its a fingerprint scanner by the way.

without it i cant communicate with the device...

Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS

you.suck = (you.passion != Programming)

Re: WTF??? AccessViolationException Issue

Rob Philpott1-Apr-08 22:46

Rob Philpott

1-Apr-08 22:46

Ah, what form does this SDK take and how do you call it?

Regards,
Rob Philpott.

Re: WTF??? AccessViolationException Issue

Harvey Saayman1-Apr-08 22:57

Harvey Saayman

1-Apr-08 22:57

its a class, first i add a reference to the project, then a using zkemkeeper;, then i make an instance of the class and the call methods from that instance in this fassion.

private void button1_Click(object sender, EventArgs e)
{
    CZKEMClass zkSDK = new CZKEMClass();
    if (zkSDK.Connect_Com(1, 1, 115200)) //connection was succesfull
    {
        if (zkSDK.ReadAllGLogData(1)) //this method gets all the data from the device and puts it in my ram
        {
            int badgeNo = 0;
            int verifyMode = 0;
            int inOutMode = 0;
            string dateTime = "";

            while (zkSDK.GetGeneralLogDataStr(1, ref badgeNo, ref verifyMode, ref inOutMode, ref dateTime))
            {
                MessageBox.Show(badgeNo + "\r\n" + verifyMode + "\r\n" +inOutMode + "\r\n" + dateTime);
            }
        }
        zkSDK.Disconnect(); //disconnect the conection
    }
}

Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS

you.suck = (you.passion != Programming)

Re: WTF??? AccessViolationException Issue

Rob Philpott1-Apr-08 23:04

Rob Philpott

1-Apr-08 23:04

Hmm. Is that a normal .NET class or a COM wrapper?

If you've defined some COM/unmanaged interop and you haven't got it quite right things like this can happen. Memory can get corrupted and your application can leak. Usually horrid things like calling conventions and the like.

If you're just using this 3rd party stuff without defining any interop yourself I think you can probably assume that is a problem with that and not you. Managed code just can't raise exceptions like the one you're getting.

Regards,
Rob Philpott.

Re: WTF??? AccessViolationException Issue

Harvey Saayman1-Apr-08 23:23

Harvey Saayman

1-Apr-08 23:23

that is literaly all i do hey...

the reference i add is a dll and while hovering over it it says "active x control for zk embedded fingerprint T7A system"

Harvey Saayman - South Africa
Junior Developer
.Net, C#, SQL
think BIG and kick ASS

you.suck = (you.passion != Programming)

Re: WTF??? AccessViolationException Issue

Victor van Hagen6-Apr-08 2:56

Victor van Hagen

6-Apr-08 2:56

Harvey,

When using classes from interop assemblies (like CSKEMClass) you, as a developer, are responsible for cleaning up any resources you use in your program. Not doing so might cause AccessViolationExceptions and will leak memory because the memory isn't freeed properly.

Try using the following pattern:

CZKEMClass zkSDK = new CZKEMClass();<br />
  // do you stuff<br />
zkSDK.Disconnect(); //disconnect the conection<br />
<br />
Mashal.ReleaseComObject(zkSDK); // This is vital!<br />

Hope it helps.

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