C# Discussion Boards - CodeProject

16-Dec-04 22:06

hey...i have a bluetooth receiver attached to my PC's USB port. How can i access it through code...I wanna do things like search for devices in the raqnge, change the visible/invisible status, turn the device on on/off etc?

Interfaces...duhhh!

Mridang Agarwalla16-Dec-04 21:52

16-Dec-04 21:52

hey...could anyone tell me what are interface and how do u use them...eg Idisposable, Iserializable. Simplicity would be greatly appreciated.
Thanks

Heath Stewart16-Dec-04 23:29

16-Dec-04 23:29

Interfaces are contracts that ensures your implementation (either a struct - though not a good idea, unless required because of boxing when casting to that interface - or a class or another interface) implements a certain method, property, or event. Read 13. Interfaces[^] in the C# Language Specification for more details, including the difference between implicit and explicit interface implementations.

As far as how to implement certain interfaces - or rather what they do - you really need to read in the .NET Framework SDK[^] what they do. Many of the topics in the SDK documentation give examples, and there's always more abstract documentation (about how to use Framework features, like serialization and the disposable pattern) if you read Programming with the .NET Framework[^].

Reading is important. Just guessing what they do would teach you the intricacies of how those interfaces work with other classes (like how IFormatter implementations use the ISerializable interface, and that Types must be attributed with the SerializationAttribute to be serializable - ISerializable just allows you to custom serialization of your Type).

This posting is provided "AS IS" with no warranties, and confers no rights.

Software Design Engineer
Developer Division Sustained Engineering
Microsoft

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Skynyrd16-Dec-04 23:30

Skynyrd

16-Dec-04 23:30

Interfaces are the public methods/properties/events a class must have (exact same signature) in order to implement them.

For example, any class that implements IDisposable MUST implement 'public void Dispose()' method

You can cast any object into any interface it implements making it useful, among other many things, as a way of achieving polymorphism (dont know if thats the exact term in english).

Heath Stewart17-Dec-04 0:16

17-Dec-04 0:16

Skynyrd wrote:
For example, any class that implements IDisposable MUST implement 'public void Dispose()' method

That's not the only option. You can also implement it explicitly, which is how the disposable pattern recommends:

public class MyDisposableClass : IDisposable
{
  public MyDisposableClass() {}
  protected virtual void Dispose(bool disposing)
  {
    if (disposing)
    {
      // Free managed resources
    }
 
    // Free native resources always
  }
  void IDisposable.Dispose() // Explicit interface implementation - not public
  {
    Dispose(true);
    GC.SuppressFinalize(this);
  }
  ~MyDisposableClass()
  {
    Dispose(false);
  }
}

Skynyrd wrote:
You can cast any object into any interface it implements making it useful

That's not correct, either. You can cast any managed object to any managed interface it implements, but you can also cast any proxy object to any interface it may not implement in managed code if it is attributed with the ComImportAttribute. This tells the CLR to QI (COM's QueryInterface for the interface based on its compiler-generated IID (an interface GUID) - which should never be the case - or its GuidAttribute value (to remain fixed) - which is the highly recommend way of declaring interface (so that the IID never changes; for COM interop, this is required to actually refer to the interface your trying to QI for).

I know that's not the simple case the original poster was asking for, but it's still the correct information.

This posting is provided "AS IS" with no warranties, and confers no rights.

Software Design Engineer
Developer Division Sustained Engineering
Microsoft

[My Articles] [My Blog]

Stefan Troschuetz16-Dec-04 23:39

Stefan Troschuetz

16-Dec-04 23:39

An interface is somehow like an abstract base class as it defines a set of methods, properties, events and/or indexers, which have to be implemented by inheritors, but doesn't provide an implementation for its members.
The big advantage of interfaces is the allowed multiple inheritance. So classes and structures can implement multiple interfaces and interfaces themself can inherit from multiple other interfaces.
If a class or structure implements an interface, it has to provide an implementation for all the interface members. E.g. if a class implemnts the IDisposable interface, it has to provide a Dispose method.
Does this help?

www.troschuetz.de

How to create a 2nd AppDomain?

Sebastian Schneider17-Dec-04 0:09

Sebastian Schneider

17-Dec-04 0:09

Certainly.

Interfaces are "standards" which every class implementing them has to meet.

If you had an interface "ICar", the classes "Ford" and "FIAT" both would implement "ICar".

Why? Because every car has to implement ICar, since ICar is the standard for cars.

This is so every car feels the same.

Even if you practised on a FIAT, the Ford still has Accelerator, Brakes, Engine, Transmission... which are defined in ICar.

If you choose to implement an Interface, you cannot implement only part of it - you have to go the whole way (the interface would be useless otherwise).

Say you want to create an application which is extensible via PlugIns. You would then define an interface for you plugin and application, so every plugin anyone writes fits into the "socket" on the application.

So, within that application, you can call "sendMessage" on every Plugin - but one Plugin may send the message via email, another one via FTP ...

I think you get the general idea Wink | ;)

Cheers
Sebastian

kosjanne16-Dec-04 21:47

kosjanne

16-Dec-04 21:47

I'm trying to create a 2nd AppDomain for handling remotingserver stuff. What am I doing wrong here:

AppDomainSetup info = new AppDomainSetup();
info.ApplicationBase = "file:///" + System.Environment.CurrentDirectory;
AppDomain dom = AppDomain.CreateDomain("DataHandler", null, info);
BindingFlags flags = (BindingFlags.Public | BindingFlags.Instance | BindingFlags.CreateInstance);
ObjectHandle objh = dom.CreateInstance("CommunicationServer", "CCommunicationServer", false, flags, null, null, null, null, null);
Object obj = objh.Unwrap();
CCommunicationServer h = (CCommunicationServer)obj;
h.BeginRemoting();

Then I have the remoting server class which I have compiled as a dll:

public class CCommunicationServer : MarshalByRefObject
{
...
}

When I call dom.CreateInstance("...); I get an exception saying: Could not load type CCommunicationServer from assembly CommunicationServer.

Have I understod something wrong here? Should I use AppDomain.Load() or something? Can you please give me a basic example how to get a 2nd AppDomain running.

Thank you.

Re: How to create a 2nd AppDomain?

Heath Stewart16-Dec-04 23:39

Re: How to create a 2nd AppDomain?

16-Dec-04 23:39

First of all, don't prefix your classes with "C". This is inconsistent with the .NET Framework. A good RAD (rapid application development) environment requires consistency. Read the Naming Guidelines[^] for more details. Hungarian notation is obsolete in the .NET Framework naming conventions (and CLI).

Is the CCommunicationServer class the fully-qualified class name? If it is defined within a namespace you must specify that as well. If you're getting a TypeLoadException then that indicates the assembly was loaded but the Type (your class) was not found. AppDomain.CreateInstance throws the FileNotFoundException when the assembly isn't resolvable. The documentation indicates as much.

You might also consider setting the AppDomainSetup.ConfigurationFile property to allow your application to use a .config file. These are more important than using them for Remoting configuration data as I mentioned in a previous post to you. You can also redirect assembly bindings and configure other runtime settins as well. It definitely leaves you open to other possibilities. And, once again, configuring your remoting server via a configuration file is far more flexible than hard-coding it. Read about the Remoting Settings Schema[^] in the .NET Framework SDK for more details.

This posting is provided "AS IS" with no warranties, and confers no rights.

Software Design Engineer
Developer Division Sustained Engineering
Microsoft

[My Articles] [My Blog]

kosjanne17-Dec-04 0:07

kosjanne

17-Dec-04 0:07

Thanks. Adding the namespace did the trick. My next problem Smile | :)

is firing events from the 2nd appdomain to the "main" domain, and I'd like to know is that even possible, so that I don't waste my time?

And thanks also for the naming guidelines, I will check in to that. And now that I have the 2nd appdomain running, I will modify the remoteserver so that it'll use the configuration file. BTW, why is it so important to use AppDomainSetup.ConfigurationFile?

Thank you.

Here: Rose | [Rose]

Have a rose for you trouble Smile | :)

Re: How to create a 2nd AppDomain?

Heath Stewart17-Dec-04 0:21

finding the program files directory

17-Dec-04 0:21

It is possible. And it's called... .NET Remoting. Smile | :)

Remoting is a managed RPC framework for communicating between context boundaries. Separate AppDomains - whether they are in the same process or not - are most definitely context boundaries.

Fortunately, the .NET Framework implements a default cross-domain remoting channel but it's pretty limited. Some in-depth research into remoting should mention this, but you should find more information in Ingo Rammers "Advanced .NET Remoting". See http://www.ingorammer.com[^].

This posting is provided "AS IS" with no warranties, and confers no rights.

Software Design Engineer
Developer Division Sustained Engineering
Microsoft

[My Articles] [My Blog]

Mridang Agarwalla16-Dec-04 21:39

Re: finding the program files directory

16-Dec-04 21:39

how can u find out the program files directory in .NET eg (C:\Program Files)

Mathew Hall16-Dec-04 22:36

Mathew Hall

16-Dec-04 22:36

System.Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles)

"I think I speak on behalf of everyone here when I say huh?" - Buffy

a problem of code pucker ?

sssa200016-Dec-04 21:32

sssa2000

16-Dec-04 21:32

i do not know how to describe , my English is very poor, so i call it "code pucker" .
Like the vs.net's IDE , you can click the node which at left side of every "{" to pucker the code .

i am very interesting on it , but i am a beginner, i try to read the source code of SharpDevelop, but i feel it was diffcult to me, can you help me?
thanks very much!

Autocomplete

Mridang Agarwalla16-Dec-04 21:28

triggering events by code

16-Dec-04 21:28

has anyone seen a really great piece of auto complete code? For those of you who dont know what autocomplete is :
'Suppose u have a combobox in which u have a few items added to the collection like "Hello", "Hi" , "Doggone". Now when u type "H" in the box the combobox automatically fills in "ello" for you. So u dont have to type the entire word.

Mridang Agarwalla16-Dec-04 21:22

Re: triggering events by code

16-Dec-04 21:22

i have a checkbox on my form and i have written a few lines of code on the checkbox.checkchanged event which fires everytime u check or uncheck the box. This works fine till u check it by clicking on it at runtime but the event doesnt fire when I type checkbox.checked = true. How cn i make the event fire through code..

Jay Shankar16-Dec-04 22:43

Jay Shankar

16-Dec-04 22:43

If checkbox.Checked is already true, and you write the checkbox.checked = true, then checkbox.checkchanged will not fire, since the checkState is not being changed, Otherwise it will fire.
Check using the statement like

this.checkbox.Checked = !this.checkbox.Checked;

BTW, If you want to call the eventHandler from any where else call like below

this.checkBox1_CheckedChanged(this, new System.EventArgs());

Re: triggering events by code

Mridang Agarwalla19-Dec-04 23:49

Re: triggering events by code

19-Dec-04 23:49

hi jay,
my code doesnt seem to fire when i type checkbox1.checked = true; even thouhg my checkbox state is false.
please subscribe to this thread so i can reply

Jay Shankar20-Dec-04 13:41

Jay Shankar

20-Dec-04 13:41

Hi Mridang,

First of all, please go through the msdn documents CheckBox.CheckedChanged[^]

It should fire. There is no bug in the .net, concerning this.

As I said in my previous post, check using again.

this.checkbox.Checked = !this.checkbox.Checked;

private void ChangeCheckBoxState(CheckBox cbx)
{
	cbx.Checked = !cbx.Checked;
	
	System.Diagnostics.Debug.WriteLine("checked state transformed to  " + this.checkBox1.Checked);
}


//

private void checkBox1_CheckedChanged(object sender, System.EventArgs e)
{
	MessageBox.Show("Check Changed");

}

You can explicitly also call the event handler, just to reconfirm as

this.checkBox1_CheckedChanged(this, new System.EventArgs());

I would also advice you to prepare a simple demo project to check the above phenomenon.

Regards,

Jay.

window class name

NikoTanghe16-Dec-04 20:37

NikoTanghe

16-Dec-04 20:37

anyone knows how I can change the window class name of a winform?

now I get something like "WindowsForms10.Window.0.app4"

Re: window class name

Heath Stewart16-Dec-04 23:57