Re: Passing a Graphics object - C# Discussion Boards

Re: ?How add a database to my c# project?

20-Jun-09 11:26

Well, the real question is, what database do you use ? An Access DB can possibly be just distributed, but a SQL Server DB needs SQL Server to be installed, a connection string configured, etc.

Christian Graus

Driven to the arms of OSX by Vista.

"! i don't exactly like or do programming and it only gives me a headache." - spotted in VB forums.

I can do things with my brain that I can't even google. I can flex the front part of my brain instantly anytime I want. It can be exhausting and it even causes me vision problems for some reason. - CaptainSeeSharp

H.R(Hamid reza)21-Jun-09 2:29

H.R(Hamid reza)

21-Jun-09 2:29

Dear christian
Thanks for your answer
Now i have a sql DB that connected to my C# program and have app.config file for DB connection
Whether if i create a setup project from my software and install it on another computer
my DB copy to new computer or not ?

Passing a Graphics object

Member 95042020-Jun-09 10:39

Member 950420

20-Jun-09 10:39

I want to make a game draw its Board so I have been trying to pass the graphics object. I get an error saying that the

NullReferenceException
"Object reference not set to an instance of an object."

I use

In the form's Paint function

Graphics g = this.CreateGraphics();
game.DrawBoard(g);

game is a variable in the form and DrawBoard is a function of that class

public void DrawBoard(Graphics g)
{
....
}
I have also tried passing the PaintEventArgs e with the same result

It works if I make the function belong to the form but that is not what I want to do

I vaguely remember from C++ that I might need to use handles but I have not been able to find a solution.

Can anybody help?

Alan

0x3c020-Jun-09 10:49

0x3c0

20-Jun-09 10:49

Chances are your game variable isn't instantiated

Between the idea
And the reality
Between the motion
And the act
Falls the Shadow

Member 95042020-Jun-09 11:56

Member 950420

20-Jun-09 11:56

Thanks everybody.

I had instantiated game in the Form load function but that must have ben too late.

I understood the debugger to be telling me that the Graphics object was Null. I never thought of the game object being Null

Finally, Why is CreateGraphics() wrong? It's use is in all the "how to do it pages on Google" I only vaguely knew about the possibility of using e.Graphics from using C++

Alan

Luc Pattyn20-Jun-09 12:14

Luc Pattyn

20-Jun-09 12:14

Hi,

Member 950420 wrote:
I understood the debugger to be telling me that the Graphics object was Null

The exception provides line information when available (normally so while debugging); and of course you have set your Visual Studio editor to always show line numbers (menu Tools/Options/TextEditor/AllLanguages:display line numbers), so you immediately can tell which line went wrong.

Member 950420 wrote:
Why is CreateGraphics() wrong?

CreateGraphics() creates a new, large, complex object, whereas the one in PaintEventArgs is already there. And the one you got from CreateGraphics() needs to be Dispose()d of, otherwise you will run into delayed memory collection situations; anyhow it will slow down your app in case you have frequent repaints (e.g. when animating something).

Member 950420 wrote:
how to do it pages on Google

Whatever you find on the Internet may or may not be correct; lots of examples are incorrect, i.e. they seem to function but contain fundamental flaws that will show under some circumstances. Read a serious book on the topic of interest, read some top-notch articles, and read the documentation, then judge everything you encounter for yourself.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

Christian Graus20-Jun-09 11:29

20-Jun-09 11:29

Member 950420 wrote:
Graphics g = this.CreateGraphics();

This is wrong. Never do it. Instead, handle the paint event, and use the graphics object passed in to that. Otherwise, if your form is obscured and then shown again, it will not redraw itself.

Member 950420 wrote:
I have also tried passing the PaintEventArgs e with the same result

Yes, that is the ONLY way to do it, unless you're drawing rubber bands or other things you want to lose easily by calling Invalidate().

Member 950420 wrote:
NullReferenceException
"Object reference not set to an instance of an object."

and, as someone already said, this ALWAYS means an object is null. You should learn to use the debugger, then you'd be able to work out which objects are not initiated, by stepping through the code.

Need a container like visual studio toolbox.

Luc Pattyn20-Jun-09 11:29

Luc Pattyn

20-Jun-09 11:29

Hi,

don't use CreateGraphics except for very special circumstances; use the Graphics that is inside PaintEventArgs instead.

chances are the Paint event fires before your game has been fully initialized, so add a null test on game inside the Paint handler.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

hdv21220-Jun-09 10:38

hdv212

20-Jun-09 10:38

Hi i'm looking for a container control like visual studio toolbox, which on mouse over, it display content controls and on mouse leave, it hide it's content.
can anybody help me ?
Note : i want to add some controls like textBox,comboBox, ... to it, not toolStrip or toolBar controls.
thanks

Re: Need a container like visual studio toolbox.

Christian Graus20-Jun-09 11:29

Re: Need a container like visual studio toolbox.

20-Jun-09 11:29

Nothing exists, unless it's in a CP article or third party library. Search CP, and then consider if you need to write it yourself.

hdv21220-Jun-09 12:01

hdv212

20-Jun-09 12:01

Hi Christian
i don't know what's the name of this control to search it.
can u help me ?

Re: Need a container like visual studio toolbox.

Christian Graus20-Jun-09 12:48

Windows Service Controlle in VS2008

20-Jun-09 12:48

I have no idea either, except that you'd probably search based on behaviour 'Visual Studio toolbox control', for example.

Whitaker.Mike20-Jun-09 5:10

Whitaker.Mike

20-Jun-09 5:10

Hi,

I hope some one out there can help me! I have been goggling my brains out all day tiring to find the answer for this question I have:

I'm using visual studio 2008 and I am pretty much a noob to c#. So go easy on me.
Trying to write a console app that checks the status of a windows service and if it is up stops it and if it's down brings it up! But the problem is that the book I am using to teach myself c# in vs 2008 does not describe this. And also to code that I do find on the web is for 2005 and doesn't work in 2008! I might look a bit liker this:

public static void StartService(string serviceName, int timeoutMilliseconds)
{
ServiceController service = new ServiceController(serviceName);
try
{
TimeSpan timeout = TimeSpan.FromMilliseconds(timeoutMilliseconds);

service.Start();
service.WaitForStatus(ServiceControllerStatus.Running, timeout);
}
catch
{
// ...
}
}

But as I stated earlier the ServiceController class doesn't seem to work in 2008, or I could just be a dim whit...

So any idea you might have as of how I might do this would make my day!
Thanks in advice,

Mike

ProtoBytes20-Jun-09 5:34

ProtoBytes

20-Jun-09 5:34

If you are not getting an exception how do you know the service has not started?

Depending on what OS you are on, the OS properties are reported diffrently.

Take a look at the win32 to .NET API cross refrence.

Microsoft Win32 to Microsoft .NET Framework API Map[^]

DaveyM6920-Jun-09 9:40

DaveyM69

20-Jun-09 9:40

I could be way off here but if you're using Vista (or possibly Weven), IIRC you can only stop and start services if you add a manifest file and elevate to administrator (yeah - that brings in the UAC prompt for your app).

It's a long time since I've tried this so I may be wrong, but I think that this is the case, and also if my memory serves correctly, you don't get any exception - it just doesn't work.

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)
Why are you using VB6? Do you hate yourself? (Christian Graus)

Shukla Rahul20-Jun-09 10:09

Shukla Rahul

20-Jun-09 10:09

Hi Mike,

It did work for me on VS 2008. Here is my program -
using System;
using System.ServiceProcess;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
try
{
ServiceController service = new ServiceController("<<Your Service Name>>");
service.Stop();
TimeSpan timeout = TimeSpan.FromMilliseconds(10000);
service.WaitForStatus(ServiceControllerStatus.Stopped, timeout);
if (service.Status == ServiceControllerStatus.Stopped)
{
service.Start();
}
}
catch
{
// ...
}
}
}
}

Are you getting any specific error ?