Re: Casting from a Type object [modified] - C# Discussion Boards

polishprogrammer10-Dec-07 11:14

10-Dec-07 11:14

I need to have a sound play in response to some internal event. I know how to play .wav files of any sort, but I don't want to play a .wav file..just send a beep. I think there's some unicode command that will do it, but if anybody could give me a tip on how to do it, that would be, well, helpful.

Thanks.

Re: Creating a Sound(say, a Beep)

Ravi Bhavnani10-Dec-07 11:18

Ravi Bhavnani

10-Dec-07 11:18

Clickety[^]

/ravi

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Re: Creating a Sound(say, a Beep)

PIEBALDconsult10-Dec-07 12:20

PIEBALDconsult

10-Dec-07 12:20

Write a character 7, or use System.Console.Beep which allows specifying the frequency and duration of the beep.

Re: Creating a Sound(say, a Beep)

JoeRip10-Dec-07 14:22

JoeRip

10-Dec-07 14:22

In .NET:

using System.Media;<br />
<br />
SystemSounds.Beep.Play()

You can also play any of the other Windows sounds.

Re: Creating a Sound(say, a Beep)

polishprogrammer11-Dec-07 9:18

polishprogrammer

11-Dec-07 9:18

Thanks.

Casting from a Type object

Leonardo Pelisoli10-Dec-07 10:55

Leonardo Pelisoli

10-Dec-07 10:55

Hi,

I'd like to know if casting based on a Type object is possible. Consider the following example:

using System;

namespace ConsoleApplication1
{
    class BaseClass
    {
    }

    class ClassA : BaseClass
    {
    }

    class ClassB : BaseClass
    {
    }

    class Program
    {
        static void Main(string[] args)
        {
            BaseClass obj1 = new ClassA();
            BaseClass obj2 = new ClassB();

            Program prog = new Program();
            prog.TreatAnything(obj1);
            prog.TreatAnything(obj2);
        }

        public void TreatAnything(BaseClass obj)
        {
            if (obj is ClassA)
                TreatClass((ClassA)obj);
            else if (obj is ClassB)
                TreatClass((ClassB)obj);
            else
            {
            }
        }

        private void TreatClass(ClassA obj)
        {
            // do stuff
        }

        private void TreatClass(ClassB obj)
        {
            // do stuff
        }
    }
}

The TreatAnything function receives a BaseClass object, and is forced to check its type by the is operator before casting it and calling the appropriate function. Now, I know the example looks simplistic, but imagine there are tens of classes derived rom BaseClass. Sure, I could make tens of if clauses and call the correct function each time... What I would really love to do, though, is turn the TreatAnything function into something like this:

public void TreatAnything(BaseClass obj)
{
    Type t = obj.GetType();
    TreatClass(SomeHypotheticalCastingFunction(t, obj));
}

So the tens of if clauses would be reduced to a small number of statements. Is there any way to do this kind of thing?

In case you want to know what I'm trying to do: I made a socket that parses what is receives and builds an object which is then passed around various methods. I have a Message base class, and then several derived classes. Each derived class represents a specific type of message, whose reception puts in motion very different actions on the server side. No, I don't think it's feasible to make a virtual method Treat() on the Message class and override it on each derived class, as the actions involved require much interaction with other objects the messages know nothing about.

I thank you in advance for any suggestions you might have.

Leonardo Pelisoli

Re: Casting from a Type object

m@u10-Dec-07 11:54

m@u

10-Dec-07 11:54

Hi
You could use Reflection to invoke the appropriate method. something like this:

public class Program
	{
		public Program()
		{
			
		}
		public void DoStuff()
		{
			BaseClass obj1 = new ClassA();
			BaseClass obj2 = new ClassB();
			ProcessObject(obj1);
			ProcessObject(obj2);
		}
		void ProcessObject(BaseClass obj)
		{
			Console.WriteLine("BaseClass");
			GetType().GetMethod("ProcessObject",System.Reflection.BindingFlags.NonPublic|System.Reflection.BindingFlags.Instance,null,new Type[]{obj.GetType()},null).Invoke(this,new object[]{obj});
		}
		void ProcessObject(ClassA obj)
		{
			Console.WriteLine("ClassA");
		}
		void ProcessObject(ClassB obj)
		{
			Console.WriteLine("ClassB");
		}
	}
	public class BaseClass
	{
	}
	public class ClassA:BaseClass
	{
	}
	public class ClassB:BaseClass
	{
	}

Re: Casting from a Type object [modified]

PIEBALDconsult10-Dec-07 12:25

PIEBALDconsult

10-Dec-07 12:25

I'm not sure you need to cast at all in that case, have you tried it without casting? And why have the TreatAnything method at all?

Well, once again I've spoken too soon. But there should still be a simpler way...

modified on Monday, December 10, 2007 7:09:54 PM

Re: Casting from a Type object

PIEBALDconsult10-Dec-07 14:20

PIEBALDconsult

10-Dec-07 14:20

OK, here's another way, using Reflection as m@u suggested, but rather than going to Reflection for each incoming message (which is very costly) I do it once in a static constructor and populate a static dictionary (my latest favourite toy). It's still not as clean as I'd like, but it's fun!

namespace ConsoleApplication1
{    
    class BaseClass    {    }    
    class ClassA : BaseClass    {    }    
    class ClassB : BaseClass    {    }    
 
    class Program    
    {
        private static readonly System.Collections.Generic.Dictionary<System.Type,System.Reflection.MethodInfo> dic ;
        
        static Program
        (
        )
        {
            System.Reflection.ParameterInfo[] pi ;
            System.Type                       pt ;
             
            dic = new System.Collections.Generic.Dictionary<System.Type,System.Reflection.MethodInfo>() ;
 
            foreach 
            ( 
                System.Reflection.MethodInfo mi 
            in 
                typeof(Program).GetMethods()
            )
            {
                if ( ( mi.Name == "TreatClass" ) && ( mi.ReturnType == typeof(void) ) )
                {
                    pi = mi.GetParameters() ;
                    
                    if ( pi.Length == 1 )
                    {
                        pt = pi [ 0 ].ParameterType ;
                        
                        if ( pt.IsSubclassOf ( typeof(BaseClass) ) )
                        {
                            dic.Add
                            (
                                pt
                            ,
                                mi
                            ) ;
                        }
                    }
                }
            }
        }
 
        static void Main(string[] args)
        {            
            BaseClass obj1 = new ClassA();            
            BaseClass obj2 = new ClassB();            
 
            Program prog = new Program();            
 
            prog.TreatAnything(obj1);            
            prog.TreatAnything(obj2);        
        }
        
        public void TreatAnything(BaseClass obj)       
        {            
            if ( dic.ContainsKey ( obj.GetType() ) )
            {
                dic [ obj.GetType() ].Invoke ( this , new object[] { obj } ) ;
            }
        }       
 
        public void TreatClass(ClassA obj)        
        {            
            System.Console.WriteLine ( "A" ) ;
        }        

        public void TreatClass(ClassB obj)        
        {            
            System.Console.WriteLine ( "B" ) ;
        }    
    }
}

Re: Casting from a Type object

Leonardo Pelisoli11-Dec-07 12:14

Leonardo Pelisoli

11-Dec-07 12:14

My thanks to you both, PIEBALDconsult and m@u. That's effectively a very elegant solution to my problem.

Best regards,
Leonardo Pelisoli

C# Properties - Stack overflow.

gunner_uk200010-Dec-07 10:34

gunner_uk2000

10-Dec-07 10:34

I'm a java programmer and am not sure how to do property

This code:

public DateTime StartDate<br />
{<br />
            get<br />
            {<br />
                return this.StartDate;<br />
            }<br />
            set<br />
            {<br />
                this.StartDate = value;<br />
            }<br />
 }

creates a stack overflow, whereby if it's set like this:
projectA.StartDate = new DateTime(2007, 12, 15);

This is only call once to initalize it, however it keeps looping around inside the property and overflows the callstack.

Anyone have any ideas what I'm doing wrong?

Re: C# Properties - Stack overflow.

Luc Pattyn10-Dec-07 10:43

Luc Pattyn

10-Dec-07 10:43

gunner_uk2000 wrote:
return this.StartDate;

that is refering itself.
you probably want a member variable (say private DateTime startDate; and have your
get and set manipulate it, rather than refer itself.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

Sorry for any delays in replying, I currently don't always get e-mail notifications.

Re: C# Properties - Stack overflow.

martin_hughes10-Dec-07 10:45

martin_hughes

10-Dec-07 10:45

You need a member variable, say:

private DateTime _startDate;

and then set and get the member variable using:

get{ return _startDate; }
set{ _startDate = value; }

what you code does is to keep calling the property's setter.

"On one of my cards it said I had to find temperatures lower than -8. The numbers I uncovered were -6 and -7 so I thought I had won, and so did the woman in the shop. But when she scanned the card the machine said I hadn't.

"I phoned Camelot and they fobbed me off with some story that -6 is higher - not lower - than -8 but I'm not having it."
-Tina Farrell, a 23 year old thicky from Levenshulme, Manchester.

Re: C# Properties - Stack overflow.

hofmadresu10-Dec-07 17:17

hofmadresu

10-Dec-07 17:17

I think it should be this

private DateTime _startDate;<br />
<br />
public DateTime StartDate<br />
{<br />
    get<br />
    {<br />
        return _startDate;<br />
    }<br />
    set<br />
    {<br />
        _startDate = value;<br />
    }<br />
}

The property works as a public getter/setter, but needs to assign the value to an actual (usually private) variable.

Mouse_Click on User Control class

Fragment10-Dec-07 9:42

Fragment

10-Dec-07 9:42

I am getting a mouse click event on a User Control object, which has not been clicked or manipulated in any way, immediately after another class object, base on a User Control, is dropped in the Panel where these objects have been added.

I am using the standard Drag and Drop events to move an object around within the same Panel. I initiate the "DoDragDrop(...)" from a Mouse_Down event in the User Control object that I am dragging.

Does anyone know from where this mouse click event might originates.

real time timer

iman_kh10-Dec-07 8:53

iman_kh

10-Dec-07 8:53

hi to all, i want to do a job per 40 milisecond but i can't !;
timer component can not support this resolution ,
can i access to this resolution in other way?

Re: real time timer

nallanch_srinivas10-Dec-07 9:00

nallanch_srinivas

10-Dec-07 9:00

you can go for waitable timers

Re: real time timer

Luc Pattyn10-Dec-07 9:18

Luc Pattyn

10-Dec-07 9:18

may I suggest you read my timers article.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

Sorry for any delays in replying, I currently don't always get e-mail notifications.