Some explanation about constructor in c#

Can anyone tell me ???Why the following code is not working ?let me know some idea.

Code:

---

using System;
using System.Collections.Generic;
using System.Text;

namespace Example9
{
    class Program
    {
        static void Main(string[] args)
        {
          Public String Program();
          {
              Console.WriteLine("I am a Constructor");

              return;
          }
           
        }
    }
}

---

You have a procedure inside a procedure and that is not allowed. Is this a homework of yours?

Quote:

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Originally Posted by firoz.raj

Can anyone tell me ???Why the following code is not working ?let me know some idea.

Code:

---

using System;
using System.Collections.Generic;
using System.Text;

namespace Example9
{
    class Program
    {
        static void Main(string[] args)
        {
          Public String Program();
          {
              Console.WriteLine("I am a Constructor");

              return;
          }
           
        }
    }
}

---

---

hay firoz.raj,
i believe here that you want to create a constructor.
the constructor must be with the same name of the class, in your case it will be Program.
you added method definition inside another method, and this is wrong.

please see this link
http://www.c-sharpcorner.com/UploadF...sInCSharp.aspx

Hi Friends,
Yes i have seen.it is easy to understand.Constructor don't have return type .constructore name is as same as class name.no need to make object of the class of the class.and call to the method of class.using object.but my question is why any need of constructor ???.additional what about copy constructor ,parameterized constructor .Kindly clarify please.

Code:

---

using System;
using System.Collections.Generic;
using System.Text;


namespace TestConstructor
{
    class Program
    {
        static void Main(string[] args)
              {
            Console.WriteLine("I am the entry point of the Constructor");
            Console.Read();
            Program p = new Program();
            Console.ReadKey();
                       
                }
        public Program()
                  {
          Console.WriteLine("I am the default constructor");
                    }
       
    }
}

---

I'm not big on the c# vocabulary, so I might be misinterpreting you.

But if I am correct, I don't think your example is very useful to show the working of parametrized and copy constructors.
So here's another one:

Code:

---

using System;
using System.Collections.Generic;
using System.Text;

namespace TestConstructor
{
    class MyCustomClass
    {
        public MyCustomClass()
        {
          Console.WriteLine("I am the default constructor");
        }
               
        public MyCustomClass(string Parameter1)
        {
          Console.WriteLine("I am a copy constructor with the given parameter: " + Parameter1);
        }

        public MyCustomClass(int Parameter2)
        {
          Console.WriteLine("You can make as many copies as you like, though using different types; here's an integer: " + Parameter2);
        }
               
                /*public MyCustomClass(string Parameter3)
        {
          Console.WriteLine("This one would probably not compile because you already have used a string parameter alone.");
        }*/
               
        public MyCustomClass(string Parameter4, int Parameter5)
        {
          Console.WriteLine("But this would work again: " + Parameter4 + Parameter5);
        }
    }
}

---

Now when you would type:

Code:

---

MyCustomClass = new MyCustomClass(

---

You would get a list of overloads (copy constructors?) showing the different parameter combinations.
The use of this is that you can initialize your custom classes with dynamic values.

Hope this helps.

Also VBWire is showing an article that might interest you.
http://www.informit.com/articles/art...ay&WT.rss_ev=a

Can you tell me ? why Console.WriteLine("I am the default constructor") is not printing??? .let me know please.as i know . it is a destructor.but what is the uses of destructor in programme.simple to destroy the resources.let me clarify please.

Code:

---

using System;
using System.Collections.Generic;
using System.Text;


namespace TestConstructor
{
    class Program
    {
        static void Main(string[] args)
              {
            Console.WriteLine("I am the entry point of the Constructor");
            Console.Read();
            Program p = new Program();
            Console.ReadKey();
                       
                }
      ~Program()
                  {
          Console.WriteLine("I am the default constructor");
                    }
       
    }
}

---

actually i tested this code
and it printing I am the default constructor

How it can be printed ???I am the default constructor .it is a Destructor.it is impossible when you will put ~ sign in the constructor.it destroys the value.
Even Destructors cannot be overloaded using Function overloading.it called automatically.i want to know the difference between dispose and destructor.
that is why i posted overhere.

Code:

---

using System;
using System.Collections.Generic;
using System.Text;


namespace TestConstructor
{
    class Program
    {
        static void Main(string[] args)
              {
           
            Console.WriteLine("I am the entry point of the Constructor");
            Console.Read();
            Program p = new Program();
            Console.ReadKey();
                       
                }
      ~Program()
                  {
          Console.WriteLine("I am the default constructor");
                    }
       
    }
}

---

Firoz,
What are you trying to say? I am puzzled by your statement "How can it be printed?"

I'll admit I'm not 100% up on C#... but if I remember right, the ~ denotes the DESTRUCTOR.... which will run when you set your reference to NILL. It's the opposite of the constructor. Dispose on the other hand is a method that comes from the IDispose interface. If you implement the IDispose interface, then you end up with an additional method Dispose. What's the difference? Dispose give you a little more fine control, and is the appropriate way to properly ensure that any components used by your object is properly cleaned up, such as unmanaged resources.

The reason for this is noted in the MSDN entry for IDispose
http://msdn.microsoft.com/en-us/libr...isposable.aspx

Quote:

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Originally Posted by MSDN

The primary use of this interface is to release unmanaged resources. The garbage collector automatically releases the memory allocated to a managed object when that object is no longer used. However, it is not possible to predict when garbage collection will occur. Furthermore, the garbage collector has no knowledge of unmanaged resources such as window handles, or open files and streams.

Use the Dispose method of this interface to explicitly release unmanaged resources in conjunction with the garbage collector. The consumer of an object can call this method when the object is no longer needed.

---

-tg

Quote:

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Firoz,
What are you trying to say? I am puzzled by your statement "How can it be printed?"

---

this ("I am the default constructor"); message cannot be printed.in the following code.

Code:

---

~Program()
                  {
          Console.WriteLine("I am the default constructor");
                    }

---

Well if the ~ defines the destructor, you can't see it, no.
The destructor is fired when the application terminates.
Only when you'd run the application from the command line it would be visible.

Quote:

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Originally Posted by TheBigB

Well if the ~ defines the destructor, you can't see it, no.
The destructor is fired when the application terminates.
Only when you'd run the application from the command line it would be visible.

---

That is correct.
If you want to check if the destructor is getting fired, add
Console.Readkey() after the Console.WriteLine

That will halt program execution.

Quote:

---

That is correct.
If you want to check if the destructor is getting fired, add
Console.Readkey() after the Console.WriteLine

---

Yes really Destructor is getting fired.but i would also like to discuss.Destructor is also prevent Memory leak.Can you tell me some comment????.how it is prevent memory leak???.let me know please.

Code:

---


That will halt program execution. using System;
using System.Collections.Generic;
using System.Text;


namespace TestConstructor
{
    class Program
    {
        static void Main(string[] args)
              {
           
            Console.WriteLine("I am the entry point of the Constructor");
            Console.Read();
            Program p = new Program();
            Console.ReadKey();
                       
                }
        ~Program()
              {
            Console.WriteLine("....Cleaning Garbage to prevent Memory Leak");
            Console.ReadKey();
              }
           
       
    }
}

---

It is used to allow you to clean up any objects you used. As I noted in my post the donstructor is the OPPOSITE of the constructor. Used for destroying the object.

-tg

Quote:

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It is used to allow you to clean up any objects you used. As I noted in my post the donstructor is the OPPOSITE of the constructor. Used for destroying the object.

---

in the following example.how should i clean the form object??? .let me know please.

Code:

---

private void button1_Click(object sender, EventArgs e)
        {
            Form frm = new Form();
            frm.ShowDialog();
        }

---

Quote:

---

Originally Posted by firoz.raj

in the following example.how should i clean the form object??? .let me know please.

Code:

---

private void button1_Click(object sender, EventArgs e)
        {
            Form frm = new Form();
            frm.ShowDialog();
        }

---

---

The frm object will be cleaned up as soon as there are no references remaining to it.

In this instance, as soon as the button1_Click function completes. This is because ShowDialog opens the form as a modal form, and the method waits for it to return before exiting.

In short, you don't need to (for reasons explained in post #18)...

And it doesn't matter in the first place as it has nothing to do with the previous conversation regarding the constructor and deconstructor. You're trying to take the concept of one thing and apply it to something completely unrelated.

-tg

Quote:

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The frm object will be cleaned up as soon as there are no references remaining to it.

In this instance, as soon as the button1_Click function completes. This is because ShowDialog opens the form as a modal form, and the method waits for it to return before exiting.

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i have seen constructor is very much similar to procedure.constructor don't return value.but procedure returns void.procedure is also used to initialize a variable or object .as per programmer needs.only strong difference i have seen between constructor and procedure.constructor has same name as class name.additionl i still have some doubt regarding copy
Constructor andparameterized constructior.

Code:

---

using System;
using System.Collections.Generic;
using System.Text;

namespace Example3
{
    class semester
    {
        private int Duration;
        public semester()
        {
            Duration = 144;
        }
        public semester(int d)
        {
            Duration = d;
        }
        public void setDuration(int newDuration)
        {
            Duration = newDuration;
        }

        public static void Main()
        {
            semester java = new semester();
            semester csharp = new semester(400);  //here why it is not printing 400.
        }
    }
}

---

Why would it print? There isn't any code there that outputs anything.

But yes, the default constructor can be used to set default values for the class. And yes, you can have a parameterized constructor to pass in values to the class.

-tg

What techgnome said.
And take a look at post #5...

Quote:

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Originally Posted by Powerlord

The frm object will be cleaned up as soon as there are no references remaining to it.

In this instance, as soon as the button1_Click function completes. This is because ShowDialog opens the form as a modal form, and the method waits for it to return before exiting.

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That is not correct. Objects are not cleaned up when there are no references left to them. When there are no references left to an object it BECOMES ELIGIBLE for garbage collection. When the object actually gets cleaned up is indeterminate, i.e. the system will do it when it's good and ready.

It's also important to note that object disposal and garbage collection are related but they are NOT the same thing. Disposal is the act of releasing managed and unmanaged resources, while garbage collection is the act of reclaiming the memory occupied by an object. Before an object can be garbage collected it must be disposed. If you don't dispose your own objects yourself then their resources will remain unavailable to the system until it gets around to garbage collecting the object, which may not be until your app closes. It's for this reason that you must ALWAYS explicitly dispose any object that supports it that you create yourself. In this case, closing a form that was displayed using ShowDialog doesn't automaticlly dispose like using Show does. For that reason you MUST dispose the form yourself as soon as you are finished with it. The most appropriate code in this case would be:

csharp Code:

using (var frm = new Form())
{
    frm.ShowDialog();
}

The object created at the start of the 'using' block is automatically disposed at the end of the 'using' block. That code is functionally equivalent to:

csharp Code:

var frm = new Form();
 
try
{
    frm.ShowDialog();
}
finally
{
    frm.Dispose();
}

Note that a 'using' block includes and implicit try..finally to ensure that the object is disposed even if an exception is thrown, handled or not.