Default Property Of A Class

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Hi,

If I have created a Class for instance named Foo. How do I set a default property so for instance:

C#

Foo f = new Foo();
f = "Test";

Is it possible without having to use a constructor or having to...

C#

f.Name = "Test"

If it is is there an Attribute that needs to be set or what should the underlying Propery be called in the Foo Class for this to happen?

Thanks in advance.

Posted 3-Jan-12 6:44am

Member 8255180

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3 solutions

Solution 3

Despite I wouldn't do it, as it breaks some simple rule of OOP, you can use an implicit operator :

public class Foo
{
   public string Name { get; private set; }

   public static implicit operator Foo(string s)
   {
      return new Foo { Name = s };
   }
}

Which would allow you to write :

Foo f = "some string";

But, again, I wouldn't do it.

Posted 5-Jan-12 5:13am

phil.o

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Abhinav S · Accepted Answer · 2012-01-03T06:49:00

Solution 1

Have a look at object initializers[^].

If you class Foo contains a property called Name, you can do Foo f = new Foo{Name="Test"}

Posted 3-Jan-12 6:49am

Abhinav S

Comments

Member 8255180 3-Jan-12 12:55pm

Thank you, but is it possible using a Parameterless Constructor?

theanil 3-Jan-12 12:57pm

5+

Abhinav S 3-Jan-12 12:58pm

Thanks.

Abhinav S 3-Jan-12 12:59pm

I dont understand your question completely. Your constructor will be parameterless.

Member 8255180 3-Jan-12 14:13pm

My apologise, I didn't read the answer correctly...I meant without having to specify the Properties in the Object Initialiser. I have searched and I did not if there was an Attribute etc that I could set so, for instance f="Test" automatically goes to the Name Property

Sergey Alexandrovich Kryukov 3-Jan-12 16:58pm

You are right (I voted 5), but perhaps you were not familiar with such feature available in some languages. I simply answered -- please see.
--SA

Abhinav S 4-Jan-12 2:18am

Thanks.

Monjurul Habib 4-Jan-12 14:46pm

5!

Sergey Alexandrovich Kryukov · Accepted Answer · 2012-01-03T10:57:00

Solution 2

There is no such feature in C#. Many C# people would not even understand your question because they might be unfamiliar with this concepts know in some other languages. Not a very big loss, I would say…

—SA

Posted 3-Jan-12 10:57am

Sergey Alexandrovich Kryukov

Updated 3-Jan-12 10:59am

v2

Comments

mostafa_darwiche 3-Jan-12 17:07pm

What is the language that supports the above situation?

Sergey Alexandrovich Kryukov 4-Jan-12 11:56am

In Object Pascal and Delphi Pascal you can have default property. In C++ you can create some similar effect by defining assignment operator...
--SA

Member 8255180 3-Jan-12 17:12pm

Thank you all for your help with this. I guess, as we all do, like to make our code as clean as possible. C# is a great language but as I have seen today it does have it's limitations.

After studying the book "CLR with C#" by Jeffrey Richter I could code in the Class..

public string this[int i]
{
get{return myvalue;}
set{myvalue = value;}
}

Then in the calling method...

foo[0]="Test";

This seems to work, but why do I have to use an Indexer???

Sergey Alexandrovich Kryukov 4-Jan-12 11:59am

You don't have to. The indexer is syntactic sugar, another one. A default property is also syntactic sugar, but it does not exist in C#. You better use it only when the value of the index means something. An index can be anything: Boolean, string...

In your case all you need is some named property like "Name". What's wrong with it?
I think the topic is closed by now.
--SA