This question already has answers here:
What is the difference between a field and a property?
(33 answers)
Closed 9 years ago.
I have read msdn article about properties. They show that example of property:
// Declare a Name property of type string:
public string Name
{
get
{
return myName;
}
set
{
myName = value;
}
}
Then they say:
Once the properties are declared, they can be used as if they were
fields of the class.
What would be the difference if they just left:
public string Name;
If I had a field: private string name and wanted to have only getter? Should I declare
public string GetName(){return name;} or should use those properties somehow?
Could somebody tell me what is wrong with that example:
private int age;
public void setAge(int age){
if(age < 100)
this.age = age;
}
This from Clr Via C#
Field A data variable that is part of the object’s state. Fields are identified by their name and type.
Property To the caller, this member looks like a field. But to the type implementer, it looks like a method (or two). Properties allow an implementer to validate input parameters and object state before accessing the value and/or calculating a value only when necessary.
They also allow a user of the type to have simplified syntax. Finally, properties allow you to create read-only or write-only “fields."
Related
This question already has answers here:
What is the difference between a field and a property?
(33 answers)
Closed 9 months ago.
Similar questions has been asked a lot but it still doesn't make sense to me as I am beginner.
here is the link
What is the { get; set; } syntax in C#?
As that answer states
(I will be using age instead of "name" to avoid confusion)
Case 1
public class Genre
{
public int Age { get; set; }
}
and
Case 2:
public class Genre
{
private int age;
public int Age
{
get
{
return this.age;
}
set
{
this.age = value;
}
}
}
Both are the same things.
So for Case 1, where is private age variable?
Does it get declared in the backend.
If Yes, then what name will be assign to it?
Surely not (Age => age) Right?
It feels like,
public int Age { get; set; }
// is same thing as
public int Age;
Now, people have mentioned that one is property another is field. But they both can be used in similar way. So what is the difference on application level?
Can you please give me an example?
It feels like,
public int Age { get; set; }
is same thing as
public int Age;
Absolutely not, the first one is two functions, the setter and the getter, while the second one is a field, an integer. As a physical example of the difference, you can do ref Age in the second example, since it has a physical location in memory, but not in the first example, since it's just functions, it's code.
So for Case 1, where is private age variable? Does it get declared in the backend. If Yes, then what name will be assign to it?
Yeah, it gets generated for you by the compiler with a name you can't declare in C# because it contains invalid characters (that are valid in .Net in general). The actual name doesn't matter, just know that you can't possibly use it or collide with it.
The main difference between the two members in your last code snippet is encapsulation
See the "Encapsulation" part on this page:
https://learn.microsoft.com/en-us/dotnet/csharp/fundamentals/tutorials/oop
Hiding the internal state and functionality of an object and only allowing access through a public set of functions.
You asked about what private field gets generated if you use an automatic property. In fact the compiler will generate a private backing field usually called something like k__BackingField or similar.
For example, I created a basic class as follows:
public class Dog
{
public string Name { get; set; }
}
This definitely creates a field in the background, and I can find out by using ILSpy to decompile it and we see the following:
Notice the Name property is there as you'd expect, with its getter and setter. But notice also the k__BackingField.
When we inspect it, it is comprised of the following code:
[CompilerGenerated]
[DebuggerBrowsable(DebuggerBrowsableState.Never)]
private string <Name>k__BackingField;
So we can see that there is definitely a private field in the background being generated for the property. We can also confirm that it actually uses that field by inspecting the get_Name getter on the Name property:
[CompilerGenerated]
{
return <Name>k__BackingField;
}
The getter for the Name property indeed returns the private field that was compiler generated for us.
I think what you're stuck on is why we would do this. Basically, if you simply have a public field on a class, you're giving permission for all-and-any other classes to set and get that field without any kind of checks or balances or rules about what goes on when setting or retrieving that value. For small applications that aren't very complex, this won't create an issue for you. But in the future when you're writing bigger applications or libraries, when you want to guarantee certain functionality behaves the same way all the time, this best practice will be necessary.
There is no difference when you use them as simple variables but using a variable as property gives you the ability to perform a check or create an event handler. For example:
private int _onetoten;
public int OneToTen
{
get => _onetoten;
set
{
if ((value > 0) && (value < 11))
{
_onetoten = value;
}
}
}
This question already has answers here:
What is the difference between a field and a property?
(33 answers)
Closed 1 year ago.
So this is one of my first classes for Object-Oriented Development and my feedback for my code was that I was missing "a property" and that GetName() is a method rather than a property. I'm currently coding in c# and was wondering if anyone could explain what a property is or point me in the right direction I'd be very appreciative.
//Instance Variables
private String name;
private decimal balance;
//Variables
public AccountDetails(String name, decimal balance)
{
this.name = name;
this.balance = balance;
}
//Accessor Methods
public String GetName()
{
return this.name;
}
You could have replaced your method with property like
public string Name { get { return this.name; } }
There is basically no difference between methods and properties. Getters and setters get internally translated into standard methods such that the runtime has no idea whether some getter or setter is associated with a certain property.
However, there is an important software engineering benefit: your code tends to be easier to understand if you restrict yourself to use getters and setters with get and set semantics. I.e. do only the steps necessary to provide the respective property.
https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/properties
GeeName() is a method, could be called Getter in Java. Properties in C# work a bit differently, the declaration goes like
//no direct variable declaration
public String Name1 { get; set; }
//with variable declaration and custom getter logic
//notice, that properties don't need to implement both GET and SET (but they can)
private String _name;
private int _access_counter = 0;
public String Name2
{
get
{
_access_counter++;
return _name + _access_counter;
}
}
public String Name3
{
set
{
_access_counter--;
_name = value;
}
}
This question already has answers here:
Difference between Property and Field in C# 3.0+
(10 answers)
Closed 9 years ago.
What makes properties and Fields different when we are passing Fields as an out/ref parameter . Does the difference between the two is memory allocation?
The biggest difference is that properties or indexers may not be passed as ref or out parameter (demo).
This is because properties do not necessarily have a backing storage - for example, a property may be computed on the fly.
Since passing out and ref parameters requires taking variable's location in memory, and because properties lack such location, the language prohibits passing properties as ref/out parameters.
Properties are not like fields at all, they're like methods.
this is a field; it does not have any logic.
private int _afield;
This is a property it defines a getter and a setter.
The getter and setter are methods.
public int AField
{
get
{
return _aField;
}
set
{
_aField = value;
}
}
This is a default property.
It's exactly like the previous property and field, except it does a lot of the work for you
public int BField { get; set; }
The best way to describe properties is in terms of the idiom of "getter" and "setter" methods.
When you access a property, you are actually making a call to a "get" method.
Java
private int _myField;
public int getMyProperty()
{
return _myField;
}
public int setMyProperty(int value)
{
_myField = value;
}
int x = getMyProperty(); // Obviously cannot be marked as "out" or "ref"
C#
private int _myField;
public int MyProperty
{
get{return _myField;}
set{_myField = value;}
}
int x = MyProperty; // Cannot be marked as "out" or "ref" because it is actually a method call
This question already has answers here:
Any reason to use auto-implemented properties over manual implemented properties?
(7 answers)
Closed 9 years ago.
What is more "true": use properties with or without private fields.
I.e.
1.
class A
{
int _field;
public int Field
{
get{ return _field;}
set{_field = value;}
}
}
2.
class A
{
public int Field{get;private set;}
}
Number 2 creates a backing field automatically, so you always have a private field "behind the scenes" (although not directly accessible in the latter case).
when you create anonymous property compiler creates corresponding field for you, so it's pretty much the same, but you can access autocreated field only via property
It makes no difference - the compiler generates the property implementation for you in exactly the same way that it generates a default constructor or the code for a using statement. These two classes are nearly 100% equivalent which you can see if you decompile an auto-property (the only difference is the name of the generated backing field that the compiler uses)
class A
{
public int Field {get; private set;}
}
class A
{
int _field;
public int Field
{
get { return _field; }
private set {_field = value; }
}
}
Its completely down to your personal preference.
As has already been stated, the second creates the backing field at compile time. You would typically define a backing field your self if you wanted the property to act as a public accessor to the field, where you can add custom logic or prevent the value being modified (using the private keyword on the setter).
This question already has answers here:
Closed 11 years ago.
Possible Duplicates:
What is the difference between a field and a property in C#
Should I use public properties and private fields or public fields for data?
What is the difference between:
public string varA;
and
public string varA { get; set; }
The public property accessor gives you more flexibility in the future.
If you want to add validation to setting the value, you simply write a non-default setter. None of your other code would have to be modified.
There could also be reasons you'd want to replace the default getter with code. That can be a real pain with a public variable.
In addition to the other answers, you can also use a property to make the value read-only or even set-only:
public int Item { get; private set; } // read-only outside the class. Can only be set privately.
I have also run into situations where I later decide I want to proxy an object, or add AOP, which basically requires properties.
Public property accesses fields and internal class code through exposed getter and setter methods. A public field acesses the field directly.
Using propertys offers the potential to provide a layer of abstraction and design (ability to make set accessor protected, private).
When a property is specified and no body present an underlying private field is created by the compiler that is used to store the value against. Essentially:
private int item = 0;
public int Item {
get { return item; }
set {item = value; }
}
In general I tend to use properties for public exposed variables and fields for private. I might consider using a field if that field was accessed many times and speed was a crucial design requirement.