Type-safe indexers when inheriting from IList? - C# Discussion Boards

Re: Threads can't communicate without a while(true) loop?

22-Nov-02 17:20

Short answer, you don't BeginInvoke will cause it to run on a thread from the ThreadPool; Invoke (or just calling the delegate like any other method) will cause it to run in the same thread (ie the worker thread).

What you do is use the (Begin)Invoke method from the form instance to have it run on the same thread as the GUI.

My preferred way of doing this is to use the handler like you already are but make the [edit]~~form~~ handler[/edit] be responsible for calling Invoke on itself.

theThread.theEvent += new EventHandler(this.ThreadIsDone);
 
....
 
private void ThreadIsDone(object sender, EventArgs e)
{
  // Returns true if not running on the GUI thread
  if( InvokeRequired ) 
  {
    Invoke(
       new EventHandler(this.ThreadIsDone), 
       new object [] { sender, e }
    );
    return;
  }
 
  // Code to run when the Thread is done
}

James

- out of order -

Bog22-Nov-02 18:04

Bog

22-Nov-02 18:04

Thanks this is great, I sort of understand why it will work. The only thing is in my case, the object that I have listening for the event isn't a Form, (or any other Control). When it was instantiated, it was created on the main gui thread where the form and controls are, but it isn't a Control itself. So there's no Invoke() method or InvokeRequired within it. I suppose I could make it a Control if I have to, just to get that method.

Is there like an interface or something I can have the object use so that it will have the Invoke() method?

thanks again

"Outside of a dog, a book is Man’s best friend. And inside of a dog, it’s too dark to read."
-Groucho Marx

Re: Threads can't communicate without a while(true) loop?

James T. Johnson23-Nov-02 7:39

Re: Threads can't communicate without a while(true) loop?

23-Nov-02 7:39

Hmmm, that is a slight problem; but I'm curious if it isn't a GUI component then why does it need to run on the GUI thread? If it modifies a Control's properties or calls a Control's methods then can just use that particular control's InvokeRequired property and Invoke method to do the work.

Bog wrote:
Is there like an interface or something I can have the object use so that it will have the Invoke() method?

None that I know of.

James

- out of order -

Bog23-Nov-02 8:51

Bog

23-Nov-02 8:51

James T. Johnson wrote:
I'm curious if it isn't a GUI component then why does it need to run on the GUI thread?

The object isn't a GUI control, but in it's eventhandler for the "I'm finished" event, it creates some GUI components and adds them to some tabpages on the form. To create and add the GUI components, it needs to be one the same thread as the GIU.

Hey but your solution gave me lots of ideas, I think I can do this, thanks very much James.

btw I found the interface, it's ISynchronizeInvoke.

"Outside of a dog, a book is Man’s best friend. And inside of a dog, it’s too dark to read."
-Groucho Marx

Type-safe indexers when inheriting from IList?

Domenic Denicola22-Nov-02 16:49

Domenic Denicola

22-Nov-02 16:49

I am inheriting my class from IList as suggested earlier as a solution to my DataGrid woes. However, it struck me that I would think that it would be best if the indexer, a required property for inheriting from IList, was type-safe, i.e. returned a MyType instead of a simple object. But when I do this:

public MyType this[int index]
{
	get { return (MyType)this.myArrayList[index]; }
	set { return this.myArrayList[index] = value; }
}
object this[int index]
{
	get { return this.myArrayList[index]; }
	set { return this.myArrayList[index] = value; }
}

it gives me this: Class 'MyIListImplementor' already defines a member called 'this' with the same parameter types.

Yet I know the framework classes seem able to create indexers with non-object return values, yet still inherit from IList. Help?

-Domenic Denicola- [CPUA 0x1337]

“I was born human. But this was an accident of fate—a condition merely of time and place. I believe it's something we have the power to change…”

James T. Johnson22-Nov-02 17:33

22-Nov-02 17:33

It does seem like its impossible, but it isn't (thankfully) Big Grin | :-D

C# (and .NET) supports the ability to specify which methods/properties should be used to implement an interface.

To do so, precede the method/property name with the name of the interface and drop the visibility modifier (because interface methods must always be public).

In your case...

public MyType this[int index] {
  get { return (MyType)this.myArrayList[index]; }
  set { return this.myArrayList[index] = value; }
}

object IList.this[int index] {
  get { return this.myArrayList[index]; }
  set { return this.myArrayList[index] = value; }
}

As an aside, if you're using an ArrayList for the underlying implementation why not inherit from CollectionBase and not have to worry about implementing IList, ICollection, etc. You just need to worry about the typesafe methods for your collection.

James

- out of order -

Domenic Denicola22-Nov-02 18:09

Domenic Denicola

22-Nov-02 18:09

Thank you very much! This works great!

James T. Johnson wrote:
As an aside, if you're using an ArrayList for the underlying implementation why not inherit from CollectionBase and not have to worry about implementing IList, ICollection, etc. You just need to worry about the typesafe methods for your collection.

Right... I knew that... really Blush | :O

Methinks my lack of FCL knowledge has made me do a lot more work than I meant to. Thanks for this as well!

-Domenic Denicola- [CPUA 0x1337]

“I was born human. But this was an accident of fate—a condition merely of time and place. I believe it's something we have the power to change…”

James T. Johnson23-Nov-02 7:46

23-Nov-02 7:46

Domenic [Geekn] wrote:
Methinks my lack of FCL knowledge has made me do a lot more work than I meant to.

You are better off for it though Smile | :)

Now you know that it exists and you also learned how you can implement IList in a strongly-typed collection.

James

- out of order -

leppie23-Nov-02 2:25

23-Nov-02 2:25

Wow James, you never fail to amaze me Smile | :)

"I dont have a life, I have a program." Also, I won't support any software without the LeppieRules variable.

David Stone23-Nov-02 5:19

David Stone

23-Nov-02 5:19

Ditto here. My only problem was when he said this:
It does seem like its impossible, but it isn't (thankfully)

He didn't use the emoticon! He should have put the extra dash in there. Seriously James, you're an editor! I am really disappointed. Poke tongue | ;-P

James T. Johnson23-Nov-02 7:41

23-Nov-02 7:41

David Stone wrote:
He should have put the extra dash in there.

Blush | :O

I've gotten too used to Trillian's emoticons, I'll go hang my head in shame now.

James

- out of order -

Re: Custom Forms Designer

David Stone23-Nov-02 8:03

David Stone

23-Nov-02 8:03

It's okay James. I forgive you. Now go make a pilgrimage to the shrine of Green Alien | [Alien]

and sacrifice a Mac on the altar. Big Grin | :-D

Custom Forms Designer

Gevik Babakhani22-Nov-02 11:45

Gevik Babakhani

22-Nov-02 11:45

Dear Masters of .NET,

Does anyone have proper sample or documentation about
creating a custom forms designer like VS.NET's or SharpDevelop's designer.

I have search the NET for quite a while, but no success.
I also dug the SharpDevelop's code and found that without documentation it
is very hard to see what the developers have done.

Any help is welcome and appreciated.

C:\>csc *.cs
Microsoft (R) Visual C# .NET Compiler
error CS2001: Source file 'brains.cs' could not be found
fatal error CS2008: No [brains.cs] specified

C:\>

John Fisher25-Nov-02 10:29

John Fisher

25-Nov-02 10:29

This is a complicated task, and understanding the SharpDevelope code isn't an unreasonable way to begin your task.

If, on the other hand, you are not actually trying to duplicate all of the functionality, (maybe you only want labels, text boxes, and buttons on your forms), you could try simply writing the thing from scratch in a way that seems logical to you. This method requires using the container form's .Capture property in order to catch the clicks that normally would have set the focus to the child control, allowing you to select and move the controls.

John :D

Config files embedded in exe

BarryJ22-Nov-02 11:15

BarryJ

22-Nov-02 11:15

Since it's really easy to access resources and modify them in .net, what do people think about storing application configs inside of the .exe itself (maybe storing the first date the program was ran inside of the executable itself, granted it's easy to modify, but I'm sure other methods will be used as well). Anybody have any thoughts on this? good idea? bad idea? I just think it might be nice to have an executable with no attachment to the registry and no other required files (sans runtimes).

Re: Config files embedded in exe

Gevik Babakhani22-Nov-02 11:57

Gevik Babakhani

22-Nov-02 11:57

To my opinion the general purpose of such configuration file is the ability
to manipulating an application’s behavior whenever necessary.

I am not sure if you could modify a .NET exe/dll file without reconstructing.
Perhaps it is possible to use Soap/Binary Serialization in combination with PropertyGrid and a command line argument to do the trick. This way you create a “PropertyGrid enabled” class that holds the configuration, then you Serialize and/or DeSerialize the class when the application starts with a startup argument like /conf

Any way, this is my opinion.

C:\>csc *.cs
Microsoft (R) Visual C# .NET Compiler
error CS2001: Source file 'brains.cs' could not be found
fatal error CS2008: No [brains.cs] specified

C:\>

invoking the compiler from my own code

LongRange.Shooter22-Nov-02 9:33

LongRange.Shooter

22-Nov-02 9:33

Okay, I am unable to find all the info on this.

We are creating dynamic C# code with the assembly files and project file.
I want to pass the project to the C# compiler programmatically.

What are the steps I need to take to accomplish this?

I am at a loss as to even where to start! I'd be happy if someone can even just point me to a tutorial on this!

Thanks much fellow CP'ers.

_____________________________________________
_{The world is a dangerous place.
Not because of those that do evil,
but because of those who look on and do nothing.}

leppie22-Nov-02 12:20

22-Nov-02 12:20

System.CodeDom.Compiler & System.Reflection.Emit

Its hard, very hard to understand, but once u grasp it, its pretty easy. Look on dotnet247 Smile | :)

"I dont have a life, I have a program." Also, I won't support any software without the LeppieRules variable.

LongRange.Shooter25-Nov-02 3:37

LongRange.Shooter

25-Nov-02 3:37

Thanks for the input.

Once I get it all figured out....it sounds like a good article to publish!

Gee...I might actually get published here. Smile | :)

_____________________________________________
_{The world is a dangerous place.
Not because of those that do evil,
but because of those who look on and do nothing.}

leppie23-Nov-02 2:31

23-Nov-02 2:31

C# also has a managed compiler, but I havent used that yet.

Microsoft.CSharp.Compiler class Smile | :)

"I dont have a life, I have a program." Also, I won't support any software without the LeppieRules variable.

LongRange.Shooter26-Nov-02 4:56

LongRange.Shooter

26-Nov-02 4:56

Leppie,

First of all: I have implemented LeppieRules in all of my own system variables, so I feel fine in asking this. Smile | :)

I have the managed compiler functioning and I am 90% of the way there. It seems like you know more about reflection than I do at the moment so I was hoping you can help with this.

What I want to do is build a collection of each DLL that is to be included as references for my compiled code. I also want to make it version independant. So I thought that I could use Reflection to say "Here is the name space System" -or- "Here is the dll System.dll" then have Reflection give me that path construct to get to the System.dll location. I think this is possible via Reflection, but I keep getting lost in it when I try to find the component that can give me this answer. Confused | :confused:

Any suggestions on where to begin my easter egg hunt?

Thanks a heap,

Condor

_____________________________________________
_{The world is a dangerous place.
Not because of those that do evil,
but because of those who look on and do nothing.}

leppie26-Nov-02 6:11