Re: avoiding double invoking - C# Discussion Boards

10-Aug-04 3:25

Hy everyone!

At the moment my application avoids double invoking with Mutex and an error message.
But I do want to change this to the following:
When the user starts the application it is displayed.
When the user wants to start a second/third/.... instance of the application this is ignored (maybe even with Mutex) and the running instance is brought back into foreground.

Here is my Main()

<br />
static void Main() <br />
{<br />
  // stores mutual exclusion result (true: no instance running, false: instance running)<br />
  bool lstartok;  <br />
  Mutex lm;<br />
  // create new mutual exclusion pointer<br />
  lm = new System.Threading.Mutex(true, "SiemensNameKeyServiceMutex", out lstartok);<br />
  if (! lstartok)<br />
  {<br />
    // there is already an instance running, so tell the user and quit<br />
    MessageBox.Show("Service already activ","double invokation",MessageBoxButtons.OK,MessageBoxIcon.Error);<br />
    return;<br />
  }<br />
  // check was ok because there is no instance running<br />
  // start new instance of the SIEMENS_Basiseinheit class<br />
  Application.Run(new myapplication());<br />
  GC.KeepAlive(lm); // important! Mutual exclusion point has to be keept alive<br />
}

But now I do want to replace this MessageBox with the popup of the running instance. Meaning instead of the errormessage the running application is brought into foreground.
At the moment I am not sure how to handle this, because I am not sure if I am able to access the running application when the (not allowed) invoking of the second/third/.... instance takes place. Sigh | :sigh:

I would have tried

<br />
WindowState= FormWindowState.Normal;<br />
Show();<br />

But well, does this work or how do I "tell" the application to do this to the running instance and not to the new instance? Confused | :confused:

Thanks!
Stephan.

Nick Parker10-Aug-04 3:49

10-Aug-04 3:49

One way you could accomplish this is to get the handle to the window you want to show with the native method FindWindow, once you have that, call ShowWindow passing the handle to the window and the nCmdShow flag. The following are the P/Invoke signatures you will need:

[DllImport("user32.dll")]
static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

[DllImport("user32.dll")]
static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);

- Nick Parker
My Blog | My Articles

Stephan Wright10-Aug-04 4:02

10-Aug-04 4:02

I can't add a refernce to user32.dll because it says it is either an invalid COM or dll.

Nick Parker10-Aug-04 4:21

10-Aug-04 4:21

Stephan Wright wrote:
I can't add a refernce to user32.dll because it says it is either an invalid COM or dll.

You don't use the "Add Reference" button. Like I said, they are native functions, so they are already compiled. The user32.dll is already on your computer, in the Windows\System32 path. I would recommend you read the Platform Invoke Tutorial[^] for more understanding of what is taking place to make these native function calls.

- Nick Parker
My Blog | My Articles

Stephan Wright10-Aug-04 22:04

10-Aug-04 22:04

thanks, the code compiles correctly now, but well it does not work at the moment because either the window is not found or my parameters are wrong in the FindWindow.
So I used Marshal.GetLastWin32Error() to tell me, which error was thrown. But well the only output I do receive is "2" as the error message. OMG | :OMG:

Is there a list of errorcodes for this or what does it mean? Confused | :confused:

I tried to find out about the hashvalues of the handles and there I found out the window has hashvalue 2. But well, why is this an error?

And besides: Do I have to tell FindWindow the full pathname (meaning including the solution) which you do get when moving the mouse over the classname in debugmode or is it enough to just use the classname without the whole thing bevor this? Frown | :(

Do you or anyone else have an idea of what's wrong? Sigh | :sigh:

Thanks!
Stephan.

Stephan Wright10-Aug-04 23:45

10-Aug-04 23:45

It works now! Big Grin | :-D

Well the classname has some wired string added to the "selfdefined" name. Some numbers etc.
That was the problem, but with Spy++ I found out!

Well so at the moment just having to manage the window poping up again instead of only being shown in the taskbar again! Smile | :)

Because the window should be brought into foreground when a double invokation was found.

Stephan.

Stephan Wright11-Aug-04 7:53

11-Aug-04 7:53

I managed to do what you recommended, well almost!

I hardcoded the parameters for FindWindow, because I thought it would be the same verytime I start my application.

But I found out it isn'T, the first parameter for example changes everytime I do restart the computer. And besides it's something really strange. I thought my Window was a Form but well there were numbers and other numeric or letters. So I will have to change this to reading or receiving this from the application, but where? Maybe I don't see the wood because of all the trees anymore but I guess I am stuck again. I was able to get the Handle, the hashvalue or whatever but not the Classname of my Form. Sigh | :sigh:

Well the WindowName isn't the Problem because it's stored in the Form1.Name element and I just have to fetch this.
But where do I have to fetch the first parameter from? Could you or anyone else help me please, to automate it so I could remove the hardcoded thing!

Thanks!
Stephan.

Nick Parker11-Aug-04 9:13

11-Aug-04 9:13

Stephan Wright wrote:
But where do I have to fetch the first parameter from?

Are you talking about FindWindow? This assumes you know the name of the window text. There are other methods of getting the window HWND (Handle) however if you are writing the application you should know this (more than likely). Does that make more sense?

- Nick Parker
My Blog | My Articles

Stephan Wright11-Aug-04 20:59

11-Aug-04 20:59

Well, as I said before I should be able to get the name of the window with the Form1.Name field. What I wanted to do is trying to get the classname for my window.
Because it is something like WindowsForms10.Window.8.app88 and that's what I do not want to hardcode because this changes everytime I reboot my PC. It could be WindowsForms10.Window.8.appdd as well.
With "second instance" I ment the user shouldn't be able to invoke the same application on the same PC twice, e.g. by clicking twice on the button. If he does the running application should reappear.

So because it's the same application (but just a second instance) the classname has to be the same. So the second invokation would have the same classname (prooved via Spy++) so I should be able to get the classname from somewhere. But I am not sure where to fetch it.

I also have a mutex on the instance, maybe I could fetch the Handle from there if it is possible to use it in this context.

Stephan.

install AddIn in VS.NET2003

Anonymous12-Aug-04 2:05

Anonymous

12-Aug-04 2:05

what about if you just do the following:
add the handle hash in the registry and evey other application will be able to check it. And if it matches then the application is running. Or if the value is set, then the application is running.
But do not forget to reset the value, because otherwise you won't know if there is an application running or not!

nthevu10-Aug-04 3:08

nthevu

10-Aug-04 3:08

i downloaded and install project GotoFunction, and after i recompile source code and build new setup project for addin GotoFunction, the install package doesn't work. It doesn't add to menu Tools and doesn't appear in Add-In Manager. Please help me.
Thank you
nthevu

Re: install AddIn in VS.NET2003

Nick Parker10-Aug-04 3:56

How to change default color of Tabpage >> Answer

10-Aug-04 3:56

Your problem is very vague, have you looked through the code that you downloaded, what is it doing? Have you contacted the author of the code/article, what did he/she say? If you have a specific C# question many on here would be glad to help you.

- Nick Parker
My Blog | My Articles

sreejith ss nair10-Aug-04 2:57

sreejith ss nair

10-Aug-04 2:57

hi,
Actually i posted one queary that " How we will change the color(caption color) of a Tabpage". Unfortunately i forgot to post the answer here. So Here is the answer for " How we will change the color(caption color) of a Tabpage.

Who is going to draw ?

Tabcontrol have a properties called DrawMode. This will set or get the value that whether user or system will paint the caption.By default it is normal. Means system(OS) will paint the caption for you. If you(parent form) want to draw the caption you have to set the value of the property to OwnerDrawFixed.

You can mention DrawMode on design time or runtime like below mentioned code.

this.tabControl1.DrawMode = System.Windows.Forms.TabDrawMode.OwnerDrawFixed;

Now you mention who is going to draw the caption.

Next thing is how is going draw ?

Tab control have an event called DrawItem event which will occure when ever an area need to be painted.

eg:

this.tabControl1.DrawItem += new DrawItemEventHandler(this.tabControl1_DrawItem);

private void tabControl1_DrawItem(object sender, System.Windows.Forms.DrawItemEventArgs e)
{

Font f;
Brush backBrush;
Brush foreBrush;

if(e.Index == this.tabControl1.SelectedIndex)
{
f = new Font(e.Font, FontStyle.Bold | FontStyle.Bold);
backBrush = new System.Drawing.Drawing2D.LinearGradientBrush(e.Bounds, Color.Blue, Color.Gold, System.Drawing.Drawing2D.LinearGradientMode.Vertical);

foreBrush = Brushes.White;
}

else
{
f = e.Font;
backBrush = new SolidBrush(e.BackColor);
foreBrush = new SolidBrush(e.ForeColor);
}

string tabName = this.tabControl1.TabPages[e.Index].Text;
StringFormat sf = new StringFormat();
sf.Alignment = StringAlignment.Center;
e.Graphics.FillRectangle(backBrush, e.Bounds);
Rectangle r = e.Bounds;
r = new Rectangle(r.X, r.Y + 3, r.Width, r.Height - 3);
e.Graphics.DrawString(tabName, f, foreBrush, r, sf);
sf.Dispose();
if(e.Index == this.tabControl1.SelectedIndex)
{
f.Dispose();
backBrush.Dispose();
}
else
{
backBrush.Dispose();
foreBrush.Dispose();
}
}
}

Sory for this late posting Wink | ;)

**************************
S r e e j i t h N a i r
**************************

Re: How to change default color of Tabpage >> Answer

Nick Parker10-Aug-04 4:00

Re: How to change default color of Tabpage >> Answer

10-Aug-04 4:00

Due to the large number of posts within the C# forum I would suggest that you consider writing up your findings in an article and posting it, otherwise this post will get lost and won't provide much help for others in the future.

- Nick Parker
My Blog | My Articles

sreejith ss nair10-Aug-04 17:11

sreejith ss nair

10-Aug-04 17:11

hi,
I will do that. why i am simply holding is, i need to explore little more on these sort of controls and their default properties. thanks
Wink | ;)

**************************
S r e e j i t h N a i r
**************************

Title bar Height

Shiva_Hosa10-Aug-04 1:56

Shiva_Hosa

10-Aug-04 1:56

how to change the Height of the Title Bar for a particular application irrespective of what the user sets the height in Display properties and in Xp and Classic Styles?(in SDK, C#)

Setting a policy using c#

Freddie8310-Aug-04 1:44

10-Aug-04 1:44

Hello,

I have a cute little problem here. I want to enable the logging for login events from within my program, but I cannot find anything about that. In windows you can set it from Local Security Settings -> Local Policies -> Audit Policy.

Does anyone know how to do this? I'm really Stuck here.

Heath Stewart10-Aug-04 6:43

Heath Stewart

10-Aug-04 6:43

Those policies map to reigstry entries. I recommend you search http://msdn.microsoft.com/library[^] or http://support.microsoft.com[^] to find which registry entry that GPO entry maps to. Then changing is easy: use the Microsoft.Win32.Registry and Microsoft.Win32.RegistryKey classes, which are documented in the .NET Framework SDK and simple enough to use.

EDIT: You could also open the policy template (don't remember where it is off-hand, but that is in the MSDN and Support sites, too) and see where it is. The policy templates are pretty simple text files that you could even open in Notepad and search for to find the friendly name (i.e., what you see) and then find what registry key it maps to.

Microsoft MVP, Visual C#
My Articles

Freddie8311-Aug-04 0:51

11-Aug-04 0:51

Damn,

I wish it was that easy, but I've tried everything, and I cannot find the key.

Anyone got more ideas?

Heath Stewart11-Aug-04 2:28

Heath Stewart

11-Aug-04 2:28

Sorry to say, but that works. All the policies do is set registry keys - nothing more. With some settings, a reboot may be required, though in Windows NT the policy update cycle (default is 15 minutes) is usually sufficient.

Microsoft MVP, Visual C#
My Articles

Freddie8311-Aug-04 2:50

11-Aug-04 2:50

Okay, I found it,

the thing was that the registry key was secured, so I couldn't see it myself. Adjusting permissions edited the whole issue. Just one problem, I need to read the Default Value of the key HKEY_LOCAL_MACHINE\SECURITY\Policy\PolAdtEv, but how the hey can I do that, If I want to read a keyValue, I must supply a keyname, but the defaultvalue hasn't got any :S.

thanks for your help so far, I wouldn't have gotten this far without it.

Freddie8312-Aug-04 5:50