Re: Reading registry with windows services. - C# Discussion Boards

13-Nov-05 2:43

Hi i have a little question. I tried to read a value from a registry like the following:

RegistryKey MyReg = Registry.CurrentUser.OpenSubKey("Software\\Microsoft\\Active Setup\\Installed Components\\{44BBA840-CC51-11CF-AAFA-00AA00B6015C}");
auth = MyReg.GetValue("Username").ToString();

It actually workt in a form, i get the username in that value. But when i try to implement this in my Windows Service, it is not able to read from the value?? I can create the MyReg object but can't get the value "Username" from it.. Does anybody has an idea why? And a solution for it? You would help me alot

Greetings

Steven Bruneel

VampireLord13-Nov-05 3:09

13-Nov-05 3:09

hm after some more debugging i found out that MyReg is null for some reason...

RegistryKey MyReg = Registry.CurrentUser.OpenSubKey("Software\\Microsoft\\Active Setup\\Installed Components\\{44BBA840-CC51-11CF-AAFA-00AA00B6015C}");

if (MyReg == null)
{
auth = "wrong";
}
else
{
auth = "right";
}

I get "wrong" as result. But when i do it in a C# form it works perfect.. Just not in the Windows Service ;(

Curtis Schlak.13-Nov-05 11:33

Curtis Schlak.

13-Nov-05 11:33

I'm pretty certain that it has to do with the fact that you try to read a value from the HKEY_CURRENT_USER portion of the registry.

When you read the value from your Windows Forms applicaiton, the curent user is you. When the Windows service tries to read it, the current user is the local system account.

To get around this, open the Services control panel, right click on the appropriate service, choose the "Log On" tab, change the service's log on to your log on by choosing the "This Account" radio button and filling in the appropriate information.

I hope that helps.

"we must lose precision to make significant
      statements about complex systems."
              -deKorvin on uncertainty

VampireLord13-Nov-05 22:39

13-Nov-05 22:39

Yes i know this is possible to run the service under a different account but won't i get the problem that, if i log in with an other user in my Windows, that i will get the same username?

Dave Kreskowiak14-Nov-05 2:39

Dave Kreskowiak

14-Nov-05 2:39

The service runs under any account you put into the LogOn tab. It runs completely independant of, and it totaly oblivious to, any user logging on the system. Your service does NOT logout and log back in under the account that the user at the keyboard is using.

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

VampireLord14-Nov-05 2:45

14-Nov-05 2:45

so there is no way for getting the current username (from the person that is logged on in Windows) in a windows service then?

Accessing member variables in destructor

Curtis Schlak.14-Nov-05 3:22

Curtis Schlak.

14-Nov-05 3:22

Refer to <http: msdn.microsoft.com="" library="" default.asp?url="/library/en-us/dllproc/base/localsystem_account.asp">.

The salient point:
"The registry key HKEY_CURRENT_USER is associated with the default user, not the current user. To access another user's profile, impersonate the user, then access HKEY_CURRENT_USER."

So, if that value exists for a specific user's profile, i.e. the logged in user, you must impersonate that user and then read the key's value.

"we must lose precision to make significant
      statements about complex systems."
              -deKorvin on uncertainty

Stylez Daviz13-Nov-05 1:39

Stylez Daviz

13-Nov-05 1:39

Hello,

I'm relatively new to C# and used C++ before. Perhaps you have a solution to my problem, I couldn't find one in several books:

When I write a class in C++ like

<br />
class MyClass<br />
{<br />
	CFirst	m_First;<br />
	CSecond m_Second;<br />
	<br />
	MyClass()<br />
	{<br />
		// my constructor<br />
	}<br />
<br />
	~MyClass()<br />
	{<br />
		//my destructor<br />
		//do some work with a member variable<br />
		m_First.DoSomething();<br />
	}<br />
<br />
}<br />

This is what happens in C++ when MyClass gets instanciated:

m_First gets instanciated
m_Second gets instanciated
MyClass constructor is called

when the MyClass object gets destroyed:

MyClass destructor gets called
m_Second gets destroyed
m_First gets destroyed.

The problem in one of my C# classes is:

I wrote myself a small logger class with an internal buffer. The data only gets written to disk when the buffer is full. I use a streamwriter for this. When my destructor gets called, I want to check if theres any data left in the buffer ans write it to disk, so the user of my class doesn't have to use a close() method when he doesn't use my logger anymore. But when I try to write to the streamwriter in my destructor, I get an E/A exception. I figured out, that my streamwriter seems to be destroyed before my destructor gets called. How can I circumvent this? The IDisposable interface doesn't solve my problem because:
a) you cannot use it when you use my class as a member variable
b) it is not guaranteed that the user of my class uses it

This is the same problem as the streamwriter has. A small program like

StreamWriter sw = new StreamWriter(@"c:\hello.txt");
sw.WriteLine("Hello World");

will leave you with an empty hello.txt file when you forget to do an explicit sw.Close().

Re: Accessing member variables in destructor

S. Senthil Kumar13-Nov-05 4:31

S. Senthil Kumar

13-Nov-05 4:31

Unfortunately, there's no way around this in C#, except using IDisposable. Because .NET is a garbage collected environment, there is no way to guarantee finalization of one object before/after another. And that's why StreamWriter works the way you described.

Stylez Daviz wrote:
The IDisposable interface doesn't solve my problem because:
a) you cannot use it when you use my class as a member variable

I don't understand the reason for a). Class member variables can be types that implement IDisposable.

Stylez Daviz wrote:
b) it is not guaranteed that the user of my class uses it

You're right, but that's how most classes in the BCL work. The "using" statement can help things a bit, but not much.

In case you are interested, C++/CLI (the new MC++) has deterministic destruction (simulated by the compiler, of course).

Regards
Senthil
_____________________________
My Blog | My Articles | WinMacro

Re: Accessing member variables in destructor

Stylez Daviz13-Nov-05 5:42

Stylez Daviz

13-Nov-05 5:42

S. Senthil Kumar wrote:
I don't understand the reason for a). Class member variables can be types that implement IDisposable.

They may implement IDisposable, but how do I use it then?

I can't use using(MyClass x = new MyClass()) outside of a class' method right? And I cannot invoke x.Dispose() from my destructor because than its already too late and my member variable could have been cleaned out by the GC.

If there's no way to get around of this problem I#ll have to accept it but I don't know why it's implemented this way. It transfers resposibility to the user of the class (like calling close() or Dispose()) where in C++ for example the user could rely on the class to handle this situation. Why can't my member variables be marked as "used" so they will only be collected by the GC when my destructor has finished? I don't know how JAVA does it, maybe I'll check it out.

Re: Accessing member variables in destructor

J4amieC13-Nov-05 10:54

J4amieC

13-Nov-05 10:54

Checked this article?

http://www.codeproject.com/csharp/IDispose.asp[^]

Fair amount of info on MSDN too (one you scroll past the "classes that implement this method" bit)

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemidisposableclasstopic.asp[^]

Help in C#

myrama13-Nov-05 1:12

myrama

13-Nov-05 1:12

Hi!. I'm very new in C#. still i'm learning C#.
1) Will C# allow us to do some graphs such as tan, sin?
2) Will it support integration, differentiation and some more functions?
if so can i have some sample code pls
RAMA

Re: Help in C#

Christian Graus13-Nov-05 10:33

Christian Graus

13-Nov-05 10:33

myrama wrote:
Will C# allow us to do some graphs such as tan, sin?

Yes

myrama wrote:
Will it support integration, differentiation and some more functions?

Yes

myrama wrote:
if so can i have some sample code pls

The Graphics class contains the method to draw your points. If you type Math., the intellisense will show you all the Math functions, such as Math.Sin, Math.Cos, Math.Abs, etc.

Christian Graus - Microsoft MVP - C++

A problem about [xml-serialization and NHibernate]

[chn]striker13-Nov-05 0:53

[chn]striker

13-Nov-05 0:53

my english is so poor ....

so pardon me... XD

i got a problem since i used Nhibernate to access data.

it is in effect that xml-serialize a entity-object,

but there are something wrong when i xml-serialize the IList object by NHibernate o/r mapping framework

help me to through the dammit problem ... 3q 谢谢！

if there is anything you need,it won't be far. <<forest gump="">>

-Images not Showing in Toolbars

wgroves12-Nov-05 23:42

wgroves

12-Nov-05 23:42

Hi-

I've created an ImageList, and a Toolbar. I've 'hooked up' each toolbar button to its corresponding Image from the image list. The images are visible in design time, HOWEVER, when I build and run the application, the Toolbar Button images are NOT visible! The buttons are there, but they are blank!

Does anyone have any idea what the problem is? I've tried an imagelist of *.ico's and also an image list of *.gif's.

Any help would be greatly appreciated!

Thanks

Warwick

"I hear they've even got the internet on Computers now." - Homer Simpson

Convert to C# syntax

dabuskol12-Nov-05 20:12

dabuskol

12-Nov-05 20:12

For i = 0 To Controls.Count - 1<br />
        Select Case TypeName(Controls(i))<br />
            Case "TextBox"<br />
                Controls(i).Text = ""<br />
            Case "Label"<br />
                Controls(i).Caption = ""<br />
        End Select<br />
    Next i

Kindly Please convert it to c# syntax
~Thanks
Confused | :confused:

Allah On Acid12-Nov-05 20:52

Allah On Acid

12-Nov-05 20:52

for (int i = 0; i <= Controls.Count - 1; i++) \
{
if (TypeName(Controls(i)) == "TextBox")
{
Controls(i).Text = "";
}
else if (TypeName(Controls(i)) == "Label")
{
Controls(i).Caption = "";
}
}

Get Sharpdevelop. It is a free development environment, and it has a VB.net to C# converter.

Edit: You can get SharpDevelop at http://www.icsharpcode.net/

Pumk1nh3ad illustrates that Intelligent Design oft goes awry. - Ed Gadziemski

-- modified at 2:54 Sunday 13th November, 2005

dabuskol12-Nov-05 21:00

dabuskol

12-Nov-05 21:00

Thanks for the immediate reply but I still have the same error, we have the same syntax conversion.

The name 'TypeName' does not exist in the class or namespace 'Maintenance.Administration'

~dabuskol

Allah On Acid12-Nov-05 21:03

Allah On Acid

12-Nov-05 21:03

The automatic C# converter did not convert the TypeName function. It is exclusive to vb. try this.

for (int i = 0; i <= Controls.Count - 1; i++)
{
if (Controls[i].GetType().Name == "TextBox")
{
Controls[i].Text = "";
}
else if (Controls[i].GetType().Name == "Label")
{
Controls[i].Caption = "";
}
}

Pumk1nh3ad illustrates that Intelligent Design oft goes awry. - Ed Gadziemski

Joshua Quick12-Nov-05 22:35

Joshua Quick

12-Nov-05 22:35

Try this. It's not exactly the same code, but is more efficient and give the same results.

foreach (Control nextControl in this.Controls)<br />
{<br />
   if (nextControl != null)<br />
   {<br />
      if (nextControl is Label)<br />
         ((Label)nextControl).Text = String.Empty;<br />
      else if (nextControl is TextBox)<br />
         ((TextBox)nextControl).Text = String.Empty;<br />
   }<br />
}