Interface in C#

Michell Johnson

Hi friends ,

I want to know that i have an interface named as person what is the correct way to implement it?

interface person {      String Name     {         get;         set;      }  }

19 Replies

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Sam Hobbs14y ago
Maha, look around in this web site. There are some FreeBook chapters available; also see Free C#.Net Book Chapters and I don't know what the difference is. You can look at previous threads. You can look in the Book Reviews. After looking at all that is already available, then if you want to ask, create a new thread with a relevant subject.
0
14y ago
I wish to expand my C# knowledge. Is there any good books in the market, I do not mind the price. If it is an eBook better because I prefer eBooks.
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Sam Hobbs14y ago
I think one way of explaining an interface is that it is a standard that can be implemented many times.

For example, for each standard computer language such as C++ and C# there is just one standard but many compilers implementing that standard. Compilers can add features to a language but if the compiler does not comply with the features described in the standard then the compiler is non-standard.

An interface specifies what a class that implements the interface must do but it does not specify how it is done. An interface could define a stream but a stream could be a disk file stream, a memory stream or a network stream. The interface would for example just specify that a class must provide methods to open and close a stream and to read/write. Some streams would use a buffer but an in-memory (string) stream would not.
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Sam Hobbs14y ago
So that book's ISBN-13 is 978-0619062736. If you look in Amazon the reviews are mixed. The list price for the book is more than $100; Barnes and Noble sells it for $66 but they list a seller that is selling it new for $20. I hope you did not pay a lot for it. Note that there is a newer edition of it; hopefully the author took more time to write that edition better.

I assume that most people that buy the book buys it as a class textbook. There are not many programming books that have a list price over $100 except for specialized books containing material that is not available anywhere else.
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Vulpes14y ago
Although 'override' is not a word which one usually associates with implementing an interface member, I suspect the author may be using it in an analogous way to 'overriding' a member of an abstract class.

This is a similar procedure as you can see if we extend the previous example to include an abstract class:

using System;

interface person
{
String Name { get; set; }
}

abstract class Human
{
public abstract bool IsMarried { get; set; }
}

class Poster : person
{
public String Name { get; set; }
}

class President : Human, person
{
public String Name { get; set; }
public int Age { get; set; }
public override bool IsMarried { get; set; }
}

class Test
{
static void Main()
{
Poster po = new Poster();
po.Name = "Michell";
PrintDetails(po);
President pr = new President();
pr.Name = "Barack";
pr.Age = 50;
pr.IsMarried = true;
PrintDetails(pr);
Console.ReadKey();
}

static void PrintDetails(person p)
{
string type = p.GetType().Name.ToLower();
char initial = p.Name[0];
Console.WriteLine("{0} is a {1} and his initial is {2}", p.Name, type, initial);
}
}
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14y ago
Book and the page(please see the last page)
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Sam Hobbs14y ago
I think the word override is misleading. That could say "as long as the class provides a definition for the interface's do-nothing, or abstract, definition" and just omit the override part and it would still communicate a complete concept and be more accurate and therefore more understandable.

Can you tell us what book?
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Vulpes14y ago
There's an example in the programs we've been using:

interface person
{
String Name { get; set; }
}

Here 'Name' is a "do-nothing, or abstract, definition" of a property.

All types which implement the person interface have to provide a 'concrete' implementation of this property.

So the Poster and the President classes's concrete implementations (in the form of an automatic property) both look like this:

public String Name { get; set; }
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14y ago
I got the following sentence from a book I couldn't understand the red marked one. Please explain that one. If you can explain with example it is highly desirable.

An interface is a collection of methods (and perhaps other members) that can be used by any class, as long as the class provides a definition to override the interface's do-nothing, or abstract, definition.
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Sam Hobbs14y ago
When I was active in the CodeGuru Visual C+ forum I noticed that the MSDN examples are often complicated. I also wanted a place to put some of the stuff that I did when I answered questions. So I got the domain name SimpleSamples.info. I also had SimpleSamples.com but I do not have it now. So most of my stuff in SimpleSamples.info is C++ but the important thing is that I chose the name SimpleSamples because the MSDN samples are often so complicated.
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14y ago
Thank you very much for the example Vulpes.
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Vulpes14y ago
Here's a simple example illustrating the benefits of using an interface.

Even though the Poster and President classes have nothing to do with one another, they both implement the person interface. This enables us to write a method, PrintDetails, which takes a person as a parameter. If they didn't have a common interface, then we would have to write separate methods for each class (or a more complicated single method using Object as the parameter type) even though they both have Name properties:

using System;

interface person
{
String Name { get; set; }
}

class Poster : person
{
public String Name { get; set; }
}

class President : person
{
public String Name { get; set; }
public int Age { get; set; }
}

class Test
{
static void Main()
{
Poster po = new Poster();
po.Name = "Michell";
PrintDetails(po);
President pr = new President();
pr.Name = "Barack";
pr.Age = 50;
PrintDetails(pr);
Console.ReadKey();
}

static void PrintDetails(person p)
{
string type = p.GetType().Name.ToLower();
char initial = p.Name[0];
Console.WriteLine("{0} is a {1} and his initial is {2}", p.Name, type, initial);
}
}
0
14y ago
You are absolutely correct Sam. Many examples I saw that those are try to explain one thing and creates many problems. Good example in my view should be focus on solving the problem in the mind.
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Sam Hobbs14y ago
Probably the benefits of an interface is not clear simply because the sample is so simple. A simple sample is usually best but sometimes they are too simple to be useful. The MSDN has many samples that are so simple that they are useless. The MSDN also has some samples that are so complicated (a complete functional application) that they are too difficult to understand for the one thing that they are intended to show. So it is often difficult to get a good balance.
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Vulpes14y ago
The purpose of having an interface is to enable types which are otherwise unrelated to one another to share functionality.

You can then write generic code which applies to all types which implement the interface because you know that they must contain certain members even though they'll (usually) be implemented differently.

The purpose of the above example was to show how to implement an interface, not to demonstrate why it's useful.
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14y ago
In above programs similar output can be obtained without having a interface part so what is the purpose of having interface.
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Vulpes14y ago
Although it looks a little strange, you can implement a get/set interface property with an 'automatic' property. The following version of the program still works fine:

using System;

interface person
{
String Name { get; set; }
}

class Poster : person
{
public String Name { get; set; } // now implemented using an automatic property
}

class Test
{
static void Main()
{
Poster p = new Poster();
p.Name = "Michell";
Console.WriteLine("{0} is a poster on C# Corner", p.Name);
Console.ReadKey();
}
}
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Sam Hobbs14y ago
Yet it is possible to have:
class person { public String Name { get; set; } }

It is unfortunate that properties cannot be implemented as Auto-Implemented Properties in derived classes.
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Vulpes14y ago
You could implement it like this:

using System;

interface person
{
String Name { get; set; }
}

class Poster : person
{
private String name;

public String Name
{
get { return name; }
set { name = value; }
}
}

class Test
{
static void Main()
{
Poster p = new Poster();
p.Name = "Michell";
Console.WriteLine("{0} is a poster on C# Corner", p.Name);
Console.ReadKey();
}
}
0