Re: Error with 'System.NullReferenceException' - Managed C++/CLI Discussion Boards

Re: Error with 'System.NullReferenceException'

Newbie0017-Feb-07 10:07

Newbie00

17-Feb-07 10:07

How have you defined the em array?

Re: Error with 'System.NullReferenceException'

Christian Graus17-Feb-07 10:08

Christian Graus

17-Feb-07 10:08

em[i] is null, you probably created an array and didn't create the objects in it

Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog
"I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )

Re: Error with 'System.NullReferenceException'

thesad17-Feb-07 12:16

thesad

17-Feb-07 12:16

the em array defined so : static array<tank^>^ em;
and tank is structure :

ref struct tank {<br />
 int step_x, step_y;  <br />
 System::Windows::Forms::PictureBox^ pct;<br />
};

What do you mean saying to create objects for array? Smile | :)

Re: Error with 'System.NullReferenceException'

prasad_som17-Feb-07 15:44

prasad_som

17-Feb-07 15:44

thesad wrote:
static array^ em;

You have not initialized array here.
Array can be initialized as given in MSDN example.

array<MyClass ^> ^ MyArray = gcnew array<MyClass ^>(100);

Prasad
Notifier using ATL | Operator new[],delete[][^]

Re: Error with 'System.NullReferenceException'

thesad17-Feb-07 21:44

thesad

17-Feb-07 21:44

I wrote taht you had sad, but still at same line is that error

Re: Error with 'System.NullReferenceException'

prasad_som18-Feb-07 1:22

prasad_som

18-Feb-07 1:22

Would interesting to see, how you have done that. There are two possiblitites,
1. You have not allocated memory for it.
2. You are accessing invalid index.

Prasad
Notifier using ATL | Operator new[],delete[][^]

Re: Error with 'System.NullReferenceException'

thesad18-Feb-07 2:05

thesad

18-Feb-07 2:05

Here is all code :

<br />
#pragma once<br />
namespace Littletanks {<br />
ref struct tank {<br />
  int step_x, step_y;  <br />
  System::Windows::Forms::PictureBox^ pct;<br />
};<br />
using namespace System;<br />
using namespace System::ComponentModel;<br />
using namespace System::Collections;<br />
using namespace System::Windows::Forms;<br />
using namespace System::Data;<br />
using namespace System::Drawing;<br />
public ref class wnd_main : public System::Windows::Forms::Form {<br />
	public: wnd_main(void) {<br />
			InitializeComponent();<br />
		    }<br />
	protected: ~wnd_main() {<br />
			if (components) delete components;<br />
		    }<br />
	private: System::ComponentModel::IContainer^  components;<br />
    private: int max_x, max_y, min_x, min_y;<br />
    private: tank usr, b_usr;<br />
    private: static array<tank^>^ em; <br />
    private: static array<tank^>^ b_em; <br />
	<br />
#pragma region Windows Form Designer generated code<br />
		void InitializeComponent(void)<br />
		{<br />
			this->components = (gcnew System::ComponentModel::Container());<br />
			this->usr.pct = (gcnew System::Windows::Forms::PictureBox());<br />
			this->b_usr.pct = (gcnew System::Windows::Forms::PictureBox());<br />
			this->SuspendLayout();<br />
			// <br />
			// pct_usr<br />
			// <br />
			this->usr.pct->Location = System::Drawing::Point(235, 391);<br />
			this->usr.pct->Size = System::Drawing::Size(50, 50);<br />
			this->usr.pct->TabStop = false;<br />
			// <br />
			// pct_em<br />
			//<br />
			array<tank^>^ em = gcnew array<tank^>(10);<br />
			array<tank^>^ b_em = gcnew array<tank^>(10);<br />
			for(int i=0; i <10; i++){<br />
			  this->em[i]->pct = gcnew System::Windows::Forms::PictureBox();<br />
			  this->em[i]->pct->Location = System::Drawing::Point(250, 250);<br />
			  this->em[i]->pct->Visible = true;<br />
			  this->em[i]->pct->Size = System::Drawing::Size(50, 50);<br />
              this->b_em[i]->pct = gcnew System::Windows::Forms::PictureBox();<br />
			  this->b_em[i]->pct->Load("b_em[i]->jpg");<br />
		      this->b_em[i]->pct->Location = System::Drawing::Point(13, 64);<br />
			  this->b_em[i]->pct->Size = System::Drawing::Size(5, 5);<br />
			  this->b_em[i]->pct->Visible = false;<br />
			  this->Controls->Add(this->b_em[i]->pct);<br />
			  this->Controls->Add(this->em[i]->pct);<br />
			} <br />
			this->b_usr.pct->Load("b_usr.jpg");<br />
			this->b_usr.pct->Location = System::Drawing::Point(97, 142);<br />
			this->b_usr.pct->Size = System::Drawing::Size(5, 5);<br />
			this->b_usr.pct->Visible = false;<br />
			// wnd_main<br />
			// <br />
			this->AutoScaleDimensions = System::Drawing::SizeF(6, 13);<br />
			this->AutoScaleMode = System::Windows::Forms::AutoScaleMode::Font;<br />
			this->BackColor = System::Drawing::SystemColors::Window;<br />
			this->ClientSize = System::Drawing::Size(500, 500);<br />
			this->MaximizeBox = false;<br />
			this->MinimizeBox = false;<br />
			this->Controls->Add(this->b_usr.pct);<br />
			this->Controls->Add(this->usr.pct);<br />
			this->KeyDown += gcnew System::Windows::Forms::KeyEventHandler(this, &wnd_main::wnd_main_KeyDown);<br />
			this->Name = L"wnd_main";<br />
			this->Text = L"Little tanks ";<br />
			this->statusStrip1->ResumeLayout(false);<br />
			this->statusStrip1->PerformLayout();<br />
			this->menuStrip1->ResumeLayout(false);<br />
			this->menuStrip1->PerformLayout();<br />
			this->ResumeLayout(false);<br />
			this->PerformLayout();<br />
		}<br />
#pragma endregion<br />

Re: Error with 'System.NullReferenceException'

prasad_som18-Feb-07 4:20

prasad_som

18-Feb-07 4:20

Here, you had made couple of mistakes,

thesad wrote:
array^ em = gcnew array(10);
array^ b_em = gcnew array(10);

Here, again you are defining local variables. It should be like this,

this->em = gcnew array<tank^>(10);
this->b_em = gcnew array<tank^>(10);

Again, simply defining array doesn't initializes its members, you need to allocate tank variable for each index. So, your code can be modified like this,

thesad wrote:
for(int i=0; i <10; i++){
this->em[i]->pct = gcnew System::Windows::Forms::PictureBox();
this->em[i]->pct->Location = System::Drawing::Point(250, 250);

Modify this to,

for(int i=0; i <10; i++){
em[i] = gcnew tank;//create tank object for each index
this->em[i]->pct = gcnew System::Windows::Forms::PictureBox();
this->em[i]->pct->Location = System::Drawing::Point(250, 250);
//your code follows

Prasad
Notifier using ATL | Operator new[],delete[][^]

Re: Error with 'System.NullReferenceException' [modified]

thesad18-Feb-07 4:48

thesad

18-Feb-07 4:48

thank you for your help Smile | :)

Re: Error with 'System.NullReferenceException'

Christian Graus18-Feb-07 9:11

Christian Graus

18-Feb-07 9:11

If you create a new Array, of 100 tank objects, you have an array with 100 instances of null. You need it iterate over the array, and say

myArray[x] = new gcnew tank();

to create the actual objects in the array.

where x is the index into the array ( you'd probably do this in a loop )

Re: Error with 'System.NullReferenceException'

prasad_som19-Feb-07 3:11

prasad_som

19-Feb-07 3:11

Christian Graus wrote:
myArray[x] = new gcnew tank();

Typo.

Prasad
Notifier using ATL | Operator new[],delete[][^]

Xp style problem in Visual Studio 2005

Vinod Moorkkan16-Feb-07 17:54

Vinod Moorkkan

16-Feb-07 17:54

Hi all,

I have an application in vc6,in that i am using XP style.

The way I am giving XP Style to my application is by adding an XML File

to my resource . The content of the Xml file is given below

/******************************************************************************/

<assembly xmlns="urn:schemas-microsoft-com:asm.v1"
="" manifestversion="1.0">
<assemblyidentity
version="1.0.0.0"
="" processorarchitecture="X86" name="Microsoft.Windows.YourApplication" type="win32">
<description>LitmusPro
<dependency>
<dependentassembly>
<assemblyidentity
type="win32"
="" name="Microsoft.Windows.Common-Controls" version="6.0.0.0" processorarchitecture="X86" publickeytoken="6595b64144ccf1df" language="*">

/****************************************************************************/

It is working fine in VC6 .

But, when I compile my application in Visual Studio 2005 , this is not working . How can I make it work.

Please Help me

Thanks
Vinod

Re: Xp style problem in Visual Studio 2005

Bartosz Bien20-Feb-07 20:51

Bartosz Bien

20-Feb-07 20:51

Remove the .manifest file from your resources (along with its reference in the .rc file). Then, go to Project Properties / Configuration Properties / Linker / Manifest File, and set Generate Manifest to Yes. Don't forget to call InitCommonControls in your InitInstance function.

This is not a C++/CLI question though, so you're in a wrong forum. Use Visual C++ / MFC[^] forum to discuss non-.NET C++ issues.

Regards,
BB
http://spin.bartoszbien.com

Serial Port - Remote Control

frozenice16-Feb-07 11:24

frozenice

16-Feb-07 11:24

hey folks

I just found this old remote control from Pinnacle Systems and wanted to code an application (in C++/CLI) which uses the RC, means: respond to key presses on the RC (volume up/down etc).
It has an infrared receiver (no extra power or so is needed), which I connected to my serial port (luckily I got one on my new computer!).
The question is, how can I receive messages?
I already opened the port (COM1), but no messages were received Frown | :(

Is there any driver-stuff I need or something?
any C++/CLI code is appreciated!

thx in advance Smile | :)

problem with Random

thesad15-Feb-07 7:46

thesad

15-Feb-07 7:46

I had written a program and I need use Random class, so I wrote :

Random^ i = gcnew Random();<br />
for(int i=0; i<10; i++) {<br />
  em[i]->pct->Left = i->Next(min_x, max_x);<br />
  em[i]->pct->Top = i->Next(min_y, max_y);<br />
}

em is static array< tank^ >^ em;
and tank is :

ref struct tank {<br />
  int step_x, step_y;  <br />
  System::Windows::Forms::PictureBox^ pct;<br />
};

but I get an error : error C2227: left of '->Next' must point to class/struct/union/generic type type is 'int'

Where is problem??

Re: problem with Random

Christian Graus15-Feb-07 8:14

Christian Graus

15-Feb-07 8:14

thesad wrote:
em[i]->pct->Left = i->Next(min_x, max_x);

i needs to be a number, an index into the array. Instead, it's an instance of the Random class.

Re: problem with Random

thesad15-Feb-07 8:28

thesad

15-Feb-07 8:28

thanks for your help Smile | :)

Email Messages

Programm3r15-Feb-07 2:23

Programm3r

15-Feb-07 2:23

Hi all,

Could someone please give me a short insight or web reference on the following: how to get notified when a new email message has arrived (MS Outlook) using VC++.

Many thanx in advance.
Regards,

The only programmers that are better than C programmers are those who code in 1's and 0's..... Smile | :)

Programm3r

Re: Email Messages

prasad_som15-Feb-07 2:39

prasad_som

15-Feb-07 2:39

Shouldn't this qualify for cross post and wrong forum ? Smile | :)

Prasad
Notifier using ATL | Operator new[],delete[][^]

Re: Email Messages

Programm3r15-Feb-07 21:03

Programm3r

15-Feb-07 21:03

Not sure .. what do you think?

The only programmers that are better than C programmers are those who code in 1's and 0's..... Smile | :)

Programm3r

Re: Email Messages

prasad_som15-Feb-07 21:40

prasad_som

15-Feb-07 21:40

Yesterday, you have asked same question in VC++ forum, which is right forum for this question. Did you say CLI or managed C++ some where ?

Prasad
Notifier using ATL | Operator new[],delete[][^]

Re: Email Messages

ThatsAlok21-Feb-07 6:20

ThatsAlok

21-Feb-07 6:20

Programm3r wrote:
insight or web reference on the following: how to get notified when a new email message has arrived (MS Outlook) using VC++.

you have to look MSoutlook com interface for that... try googling Smile | :)

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
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capture s-video from my pinnacle pci card to borland c++

bozzim14-Feb-07 22:40

bozzim

14-Feb-07 22:40

Can sombody help, i need source for capturing s-video from my pinnacle pci card to borland c++. Or can sombody tell me where to begin if i write it myself. Because i dont know how link other applications ed.

bozzim

Re: capture s-video from my pinnacle pci card to borland c++

Christian Graus15-Feb-07 0:15

Christian Graus

15-Feb-07 0:15

Borland doesn't do C++/CLI AFAIK, so odds are, you're in the wrong forum. Try the visual C++ forum, but even then, Borland means you're pushing it to find someone here who can help.

FileLength

Vichitram14-Feb-07 20:37

Vichitram

14-Feb-07 20:37

Hi,
Does anyone know the function to get the Length of a file in CPP (Win32 Console Application).

Regards,
Vichitra

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