Re: Question about Objects - C# Discussion Boards

Blubbo7-Sep-06 3:13

7-Sep-06 3:13

I'm working on CRX14 communication. I have this dll that was written in c++ language ("CRX14USBDLL.dll").

The c++ dll function is:
Get_HID_StringDescriptors(char VendorN[100], char ProductN[100], char SerialN[100])

Now in my c# code:

I dllimported this dll as:
[DllImport("CRX14USB.dll") public static extern void Get_HID_StringDescriptors(char[] VendorN, char[] ProductN, char[] SerialN);

now with the variable declarations:
char[] VendorN = new char[100];
char[] ProductN = new char[100];
char[] SerialN = new char[100];

Now to call the dll function:
Get_HID_StringDescriptors(VendorN, ProductN, SerialN);

to display the variable in message box:
messText = VendorN + ", " + ProductN.ToString() + ", " + SerialN.ToString();
MessageBox.Show(messText);

Am i doing anything wrong here? Anyone can help?

Re: Passing char array to c++ function

Nader Elshehabi7-Sep-06 4:48

Nader Elshehabi

7-Sep-06 4:48

Hello

Blubbo wrote:
Am i doing anything wrong here? Anyone can help?

You didn't specify what error do you get of this code?

Regards

Re: Passing char array to c++ function

Judah Gabriel Himango7-Sep-06 4:57

Judah Gabriel Himango

7-Sep-06 4:57

Try passing a string into the native method, rather than a char[]. Also, if the native method modifies the string in anyway, you'll need to pass in a StringBuilder

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Re: Passing char array to c++ function

Judah Gabriel Himango7-Sep-06 4:57

Judah Gabriel Himango

7-Sep-06 4:57

Try passing a string into the native method, rather than a char[]. Also, if the native method modifies the string in anyway, you'll need to pass in a StringBuilder instead of a string or char[].

Tech, life, family, faith: Give me a visit.
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Question about Objects

Chrismaster7-Sep-06 2:08

Chrismaster

7-Sep-06 2:08

Hi!
I'm assuming little problems instancing a set of sprites from a single
AnimatedSprite class using SDLdotNet with C# 2005.

let's check my Generate() function in the Stone Class:

<br />
<br />
AnimatedSprite asMySprite;<br />
<br />
public void Generate(AnimatedSprite asfOrigin)<br />
{<br />
    int iRND = Random.Next(0, 5);<br />
    asMySprite = new AnimatedSprite();<br />
    asMySprite = asfOrigin;<br />
<br />
    switch(iRND)<br />
    {<br />
    case 0:<br />
        asMySprite.CurrentAnimation = "aaa";<br />
    case 1:<br />
        .<br />
        .<br />
        .<br />
        <br />

So now my problem is, that after calling the Generate()
function, if I change some properties of the asfOrigin
structure, they are also changed in my asMySprite
structure, regardless to the fact that I am instanciating
asMySprite with the new keyword prior to copying it's
changes.

What am I doing wrong???

Thanks for help in advance,
Chris

Re: Question about Objects

SeMartens7-Sep-06 2:23

SeMartens

7-Sep-06 2:23

Hi Chris.

Within the line asMySprite = asfOrigin; you are assigning a reference of asfOrigin to asMySprite. So far the objects asMySprite and asfOrigin represent the same object, but with two different pointers to it. Calling new in the line above has no effects, because you are overwriting the l-value (reference) of asMySprite in the next line.

Maybe you should implement a clone method for AnimatedSprites, where you copy the value of asfOrigin to an assigned object (but pay attention to references).

Example:

public class AnimatedSprite {
.
.
public AnimatedSprite CopyThis(AnimatedSprite asfMyNewSprite){
asfMyNewSprite.Attribute1 = this.Attribute1;
.
.
.
}
.
}

Hope this helps you.

Regards
Sebastian

Re: Question about Objects

Not Active7-Sep-06 2:25

Not Active

7-Sep-06 2:25

asMySprite = new AnimatedSprite();
asMySprite = asfOrigin; <- Problem here

Classes are reference objects, your are saying that asfOrigin and asMySprint are referencing the same memory location at this point.

Object.ReferenceEquals(asMySprint, asfOrigin) = true

You can override the Equal operation or derive from IClonable to make a copy of the object's data to get it to behave as you are expecting.

only two letters away from being an asset

Re: Question about Objects

mikone7-Sep-06 2:26

mikone

7-Sep-06 2:26

lets say it like microsoft would: "this is not a bug, it's a feature!"

you just were introduced to the worl of object oriented programming.
the problem which has occoured is not really a problem.
the object passed to the function will be passed as a reference.
that means you will just permit its address and the function will access
the original object.
As you have just noticed there is no new object.
But stop, there is. You wrote:

<br />
asMySprite = new AdnimatedSprite();<br />

this line means you're allocating some memory on the heap for a new instance of the class animated sprite. the address of the beginning of this memory (i guess in .net its a bit different...) is assigned to the asMySprite variable. In the next line you write:

<br />
asMySprite = asfOrigin;<br />

Now you assign the address of the ORIGINAL object to the variable. this means you "overwrote" the variable and it isn't pointing to the new object anymore.
Thats why this error occurs.

To avoid this situation, you should make yourself familiar with references and "deep copies" of objects.

There is no general solution for your problem since the circumstances are different for each class...

Good luck,
mik

Thanks!

Chrismaster7-Sep-06 2:34

Chrismaster

7-Sep-06 2:34

I now copy each Attribute of one class to the other and now
it works. Thanks for your help!

Greetz,
Chris

Re: Question about Objects

guygo7-Sep-06 2:48

guygo

7-Sep-06 2:48

Hi Chris
I guess that by doing this you want to get the same values from the original object to a new object
and change its property.

well, all that says on the preveius nodes are correct.
but if i understend you correctly then to implement what you need is

you should create a contractore for your object "AnimatedSprite " which
get the values as you want
like:(in the AnimatedSprite Class)

public AnimatedSprite (string currentAnimation,string property2, string property3....)
{
        this.CurrentAnimation=currentAnimation;
	this.Property1= property1;
        this.Property2= property2;

}

then in your Generate function 
asMySprite = new AnimatedSprite(newCurrentAnimation,asfOrigin.prop2,asfOrigin.prop3);

this way you create a new instance of AnimatedSprite with the values that you want

Guy

Limiting ListObjects in Excel from growing row-wise

esskay19797-Sep-06 1:51

esskay1979

7-Sep-06 1:51

Hi Everybody,
The List Objects in Excel 2003 grow row-wise automatically as and when a user enters some value in the row next to the last list row.
Is there any way to limit this behaviour of the list object.

Hope to hear from you people at the earliest,

Thanks in Advance,
Karthick

Avoiding 2 same processes

stancrm7-Sep-06 1:48

stancrm

7-Sep-06 1:48

Hello...

I don't want to load my application more than once. That's why, I'm using GetProcessesByName.
If length of process array more than 1, that means exit, if only 1, then OK.
But someone told me that I must use Singleton.

What do you mean about that ? Is Singleton the right way ?

Re: Avoiding 2 same processes

User 66587-Sep-06 2:00

User 6658

7-Sep-06 2:00

Use a Mutex

Create it in the first instance and check at startup, if it already exists. Like that (pseudocode)

if(Mutex.Exists("MyAppMutex"))
{
    // our app is already running, exit
    Exit();
}
else
{
    // Mutex doesn't exist, create one
    Mutex.Create("MyAppMutex");
    StartApplication();
}

Here is a concrete example:
http://codebetter.com/blogs/paul.laudeman/archive/2004/07/17/19576.aspx

regards

modified 12-Sep-18 21:01pm.

framework including

erfi7-Sep-06 1:17

erfi

7-Sep-06 1:17

hi.

how i can include dotnet framework in my project setup application?

thanks.

Re: framework including

Utkarshraj Atmaram7-Sep-06 1:55

Utkarshraj Atmaram

7-Sep-06 1:55

Here is a tutorial[^]

Here is an example bootstrapper application[^]

how to call a method from another thread?

michal.kreslik7-Sep-06 0:44

michal.kreslik

7-Sep-06 0:44

Hello,

how can I safely call a method from another thread? For instance, a method that belongs to a progressbar control on my form, from a backgroundworker thread.

I've tried using events, lock, volatile but nothing worked. I always get the InvalidOperationException (Cross-thread operation not valid).

I am trying to execute the PerformStep() method of the progress bar on the main form every time a certain progress is made in the backgroundworker.

It's quite weird that I solved a similar problem with updating the status bar on the main form by using events, but that was made by assinging a string to the .Text property. Seems like in a cross-thread operation, changing properties is ok, but calling a method is not.

I know there's another way to report progress with backgroundworker, namely via the Backgroundworker.ProgressChanged event, but my question is somewhat more general: how to call a method from another thread safely?

Thanks,
Michal

Re: how to call a method from another thread?

Bijesh7-Sep-06 0:53

Bijesh

7-Sep-06 0:53

You can use the Invoke method of the control to safely execute a method on the control's thread. Generally it is not safe to do any GUI control manipulation on a non-GUI thread, you need to marshall those calls across to the GUI thread using Invoke.

--------------------------------------------------

Re: how to call a method from another thread?

michal.kreslik7-Sep-06 1:57

michal.kreslik

7-Sep-06 1:57

Thank you very much!

Invoke() method and one delegate solved the problem.

It's great there are people like you who are willing to help.

Thanks,
Michal

Windows API overriding in C#

hoangvantien7-Sep-06 0:39

hoangvantien

7-Sep-06 0:39

I just have 2 questions :
1. how to override a api function ? (i mean the technique)
2.how to do that if i use c#
Please help me !
Thanks

hoang van tien

Re: Windows API overriding in C#

Judah Gabriel Himango7-Sep-06 4:55

Judah Gabriel Himango

7-Sep-06 4:55

hoangvantien wrote:
1. how to override a api function ?

To be able to do this, the class containing the function you're interested in must have 2 requirements: the class cannot be sealed, and the function must be virtual.

If both of those conditions are met, you can inherit a class from the class containing the function you're interested in, then override the method in that class.

public class ClassYouAreInterestedIn
{
    public virtual void DoSomething() { ... }
}

public class MyOverride : ClassYouAreInterestedIn
{
    public override DoSomething() { ... }
}

Tech, life, family, faith: Give me a visit.
I'm currently blogging about: Dumbest. Movie. Title. Evaaar.
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Re: Windows API overriding in C#

Jun Du7-Sep-06 5:04

Jun Du

7-Sep-06 5:04

As API is a quite broad term (and often abused), the answer may well depend on the context of your API:

1) If API is a C API or like, there will be no overriding, as overriding only applies to OO programming. Function overloading will make sense in this case. But see 2).

2) If API is a library you load via Platform Invoke, you could only override the invoked method in your C# wrapper, not the original one. Thus, there will be no direct overriding.

3) If API is a .NET assembly (DLL), lets say, written in managed C++, you can extend the base class and override its methods if the class is derivable, thanks to the cross-language compatibility of .Net Framework.

4) If... Cool | :cool:

Best,
Jun

TreeView Control in WinForms

aka21097-Sep-06 0:26

aka2109

7-Sep-06 0:26

I am searching for a customized treeview control which has the following functionalities:

1) Word wrap for the nodes.. since i want to avoid the horizontal bars
2) For scrolling i am using two buttons.. but i m not able to bind the button click event with the scroll event of the treeview control
3) Set background image for the treeview and also set images for each node.

I m using VS 2005 and .NET framework 2.0

If anybody has developed such control, kindly send me the source code.
Any help will be appreciated

Thanks

A.K

Re: TreeView Control in WinForms

Ed.Poore7-Sep-06 0:57

Ed.Poore

7-Sep-06 0:57

Try entering TreeList or TreeView into the search bar for the CodeProject there are a couple of articles here which may do what you want, but then again may not.

As of how to accomplish this I have no idea, have you tried Google?
Faiing that try Badger | [badger,badger,badger,badger...]

Re: TreeView Control in WinForms

aka21097-Sep-06 18:31

aka2109

7-Sep-06 18:31

Hi

Can anyone tell me how to bind vertical Scroll event of treeview control with the VScrollBar scroll event?

Thanks in advance

A.K

Deleting records with child records?

kbalias7-Sep-06 0:18

kbalias

7-Sep-06 0:18

What is the best way to manage the deletion of master records that have child records? I load the data from the database into a dataset. I would like to give the users the following functionality: If a user selects a number of records to be deleted and some of them have child records, I would like to give the user the option of either skipping those with child records or deleting them (including their child records).

I am using Visual Studio 2003 and C#.

Thanks.

Kobus

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