Re: Simple problem with brackets - C# Discussion Boards

4-Aug-09 10:33

Hello all,
I have just started programming with c# (2008). The only programming experience that i have ever had is visual basic. I am only 12 years old. I have purchased a c# 2009 for dummies book and that does not seem to help my current problem. My problem is that I am unable to write things. This is what i mean:

Console.WriteLine("Enter your name:");

Above both the brackets i get a red line and a error saying "invalid token '(' in class, struct, or interface member declaration.

I also get the same message for the other bracket.

"invalid token ')' in class, struct, or interface member declaration.

I have tried everything and asked everybody however know one seems to know a solution, I would deeply appreciate if anybody woul help me.

Thank you,
Aman

modified on Tuesday, August 4, 2009 4:44 PM

VengefulSakhmet4-Aug-09 10:53

VengefulSakhmet

4-Aug-09 10:53

Hello World C#

Go through this tutorial. It should help get you on the right start. You can even download the code and try to compile that by itself. If that fails to compile then you may have issues with how your directories are set up. Best of luck!

Amangang4-Aug-09 22:49

4-Aug-09 22:49

Dear VengefulSakhmet,

Thank you very much. May i know here to find your tutorial?

Thank you,
Aman

Henry Minute4-Aug-09 22:54

Henry Minute

4-Aug-09 22:54

You see at the top of the message the 'Hello World C#' bit?

Click on it, it's a link. The different colour, sort of gives this away.

Henry Minute

Do not read medical books! You could die of a misprint. - Mark Twain
Girl: (staring) "Why do you need an icy cucumber?"
“I want to report a fraud. The government is lying to us all.”

Amangang4-Aug-09 22:59

4-Aug-09 22:59

Dear Henry Minute,

Thank you very much for the totorial, i am sure that i will find it very usefull.

Sorry for the trouble,
Aman

Amangang5-Aug-09 2:15

5-Aug-09 2:15

Dear HenryMinuite,

Man i used your totorial and i did nto find it usefull FOR my problem. The brackets still go red no matter whati try. I even trying copying and paisting it but it still does not work. I Copied the command that writes thing on the launch of the program but it still apears red. Would it help if i paist my script for you to understand and hopefully help?

Thank you,
Aman

VengefulSakhmet5-Aug-09 3:34

VengefulSakhmet

5-Aug-09 3:34

Dear Aman,

The tutorial I had posted at the top called "Hello World C#" should work correctly. Perhaps your directories and libraries are not properly set up. Take a look at: Visual Studio Getting Started. I would go to the FAQ section and look up installation procedures. Also post your full code. I assume you are trying to write a small program for starters, so it shouldn't be hard to tell if your program would compile properly in the right environment. Best of luck!

-Laurel

Amangang5-Aug-09 3:41

Casting List<concreteclass> to IList<interfaceconcreclass></interfaceconcreclass></concreteclass>

5-Aug-09 3:41

Hello,

I asumed that at first. However all my previous programs had worked properly without a error, I even copied and pasted it but the brackets still have the red line underneath. I have not touched the settings, Anyway i will look at the getting started thing. Thank you very much for helping me. I hope that it will help me a lot and fix my unusual problem.

Thank you for all your support,
Aman

Ubirajara Mendes4-Aug-09 8:49

Ubirajara Mendes

4-Aug-09 8:49

Hi Guys,

this is my first post on Code Project, becouse everything i needed help I found on this forum, but for this inssue o don't find the answer.

So, my problem is:

- I have a class that implements an Interface e.g:

public interface IMyclass
{
   string Name {get; set;}
}

public class Myclass : IMyclass
{
   private string name;
   public string Name
   {
         get { return name; }
         set { name = value; }
   }
}

In one method I need return an IList<IMyclass> created as a List<Myclass> like this:
public IList<IMyclass> CreateList()
{
   IList<Myclass> listMyclass = new List<Myclass>();
   return (IList<imyclass>)listMyclass;
}

and the code that call the class expect a return of IList<IMyclass>, but this form generate an error saying that this cast is not possible.

anyone have an idea to solve this problem? I'm using Visual Studio 2005.

Thanks.

Ubirajara Mendes

Adam Maras4-Aug-09 9:31

Adam Maras

4-Aug-09 9:31

I'm not sure why you've received an error... (please post the exact error message and text) but you should simply be able to do this:

public IList<IMyclass> CreateList()
{
   return new List<Myclass>();
}

Adam Maras | Software Developer
Microsoft Certified Professional Developer

Ubirajara Mendes5-Aug-09 9:03

Ubirajara Mendes

5-Aug-09 9:03

Hi Adam,

that is the exception:
Cannot implicitly convert type 'System.Collections.Generic.List<Teste.App.Myclass> to 'System.Collections.Generic.IList<Teste.App.IMyclass>. An explicit conversion exists (are you missing a cast?)

Ubirajara Mendes

Adam Maras5-Aug-09 11:13

Adam Maras

5-Aug-09 11:13

Ahh... I see the problem now.

Your problem is one related to covariance and contravariance[^]. Let me show you an example:

public interface IMyClass { }

public class MyClass : IMyClass { }
public class MyOtherClass : IMyClass { }

In this example, you have an interface, and two classes that implement said interface. Now, you've created a generic list of your first class type:

List<MyClass> listMyClass = new List<MyClass>();

Let's say, for the sake of this argument you weren't getting that cast error, and you could cast to a generic list of your interface type:

List<IMyClass> listIMyClass = ( List<IMyClass> )listMyClass;

Now, while only one list exists (because your cast just changed the type of the reference, not the contents of the list) you have created a reference that would allow you to add other objects that implement IMyClass to that list. Think about this:

listMyClass.Add( new MyOtherObject() );  // obviously won't work, MyObject (the list type)
                                         // and MyOtherObject (the type being added) are incompatible

listIMyClass.Add( new MyOtherObject() ); // seems like it should work, because you're adding an object
                                         // that implements IMyClass... but that list you're referencing
                                         // has a generic type of MyClass, NOT IMyClass.

The problem isn't that you're casting a List<> to an IList<>, it's that you're trying to cast from a list with one generic parameter type to another.

Adam Maras | Software Developer
Microsoft Certified Professional Developer