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What is the difference between a field and a property in C#
Can someone explain the diffrence if any between these two properties?
public string City { get; set; }
public string City;
The first one is an actual property. The second one is just a field.
Generally speaking, fields should be kept private and are what store actual data. Properties don't actually store any data, but they point to fields. In the case of the auto-property above, it will auto-generate a hidden field like _city behind the scenes to hold the data.
Hope this helps!
First one is CLR property, while the second is just public field (not a property).
In WPF and Silverlight, binding doesn't work with public fields, it works only with public properties. That is one major difference in my opinion:
//<!--Assume Field is a public field, and Property is a public property-->
<TextBlock Text="{Binding Field}"/>
<TextBlock Text="{Binding Property}"/>
First one wouldn't work but the second one would work.
as mellamokb said. the first type is Property,the compiler will auto-generate access function and private field like:
private String _city;
public String City(){ return _city ;}
.....
use Properties,you can control the access of _city,for example"
public String City(){
doXxxFunction();
return _city ;
}
so,you should always use the property,and make sure all field is private.
Related
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How do I target attributes for a record class?
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Closed 1 year ago.
With the new C# record types in C# 9 i'd like to know wheter it is possible (for serialization) to set the JsonPropertyAttribute from Newtonsoft.Json on the constructor parameter.
It doesn't seem to work out of the box.
MWE:
using System;
using Newtonsoft.Json;
Console.WriteLine(JsonConvert.SerializeObject(new Something("something")));
record Something([JsonProperty("hello")] string world) {}
Output:
{"world":"something"}
Expected output:
{"hello":"something"}
is there an easy way to make it work like this? or do we have to revert back to the property style with a real constructor?
internal record Something
{
public Something(string world) { World = world; }
[JsonProperty("hello")] public string World { get; }
}
Per the docs:
Attributes can be applied to the synthesized auto-property and its backing field by using property: or field: targets for attributes syntactically applied to the corresponding record parameter.
So you want
record Something([property:JsonProperty("hello")] string world) {}
Without the property: qualifier, the attribute ends up on the parameter of the generated constructor (which is useful in other scenarios, like nullability).
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If a class (or a structure) has a field and we replace it with an auto property of the same type, will client code always stay the same, taking into account that we don't use reflection or any other type of direct or indirect meta-programming? For example
int Integer;
public void Test() {
Console.WriteLine(Integer);
}
If I change int Integer to int Integer { get; set; }, the code that uses it stays unchanged. Is there any case when I need to change calling code?
The same question about readonly fields and get-only properties.
EDIT: I clarified my question. Also, taking into account existing answers, instead of auto property, question will be about ref property:
Is it possible to replace this
int Integer;
with
int _integer;
ref int Integer => ref _integer
Without any changes of calling code?
I want to find a case when I need to change client source code if I
replace a field with a property or opposite. I want to know how safe
this replacement is
Fields (C# Programming Guide)
Generally, you should use fields only for variables that have private
or protected accessibility. Data that your class exposes to client
code should be provided through methods, properties and indexers. By
using these constructs for indirect access to internal fields, you can
guard against invalid input values. A private field that stores the
data exposed by a public property is called a backing store or backing
field.
So there you have the official word on field and property usage
I mean, if we replace a field with auto property or opposite, do we
need to change client code in some cases
Yes, you are likely to break things in the following cases,
If you are exposing fields that are being passed by ref
If this class is being inherited and in cases where fields or properties are getting re-implemented or overridden
A derived classes implement Interfaces that require properties etc.
Also there could be cases where they are used in Expressions and it expects field or a property (I think).
In short, if large code bases relied on fields/properties and you change them this is likely to cause breakable changes for any of the above.
Though in summary, if you lived by the Microsoft recommendations above, you should have less of a problem, and if you do it points to the fact this should probably be refactored as a new version anyway (with breakable changes, and more expected usage).
This question already has answers here:
What's the difference between encapsulating a private member as a property and defining a property without a private member?
(5 answers)
Closed 6 years ago.
I came across the question in interview, defining the property in Class. I know this is very basic question but would like to get discuss with experts here.
Method 1:
public string MyProperty { get; set; }
Method 2:
private string _myProperty;
public string MyProperty
{
get
{
return _myProperty;
}
set
{
_myProperty = value;
}
}
Which will better in performance in terms of extra variable need to declare in Method2.
Both methods use the same number of variables, in the first version the extra variable is just hidden by the compiler, if you decompiled the code you would see it too uses a variable.
Method 1 is a "newer" way of doing things. It was introduced in C# 3.0. Behind the scenes it is in fact using a private backing variable... it's just neater.
https://msdn.microsoft.com/en-us/library/bb384054.aspx
Method 2 would probably perform "better" only in the cases where you needed to directly access that variable from within the class itself. But performance wise between the two, it's probably very negligible. You wouldn't need to go through the setter/getter.
However, method 1, in my opinion, just provides a better flow of control, keeps code cleaner, and ensures you're always going through a setter/getter and not directly accessing the private variable itself.
Method one is the quick way to implement it and if no extra checks have to be done then that can be used. However, option two is used when you want to sanitize inputs to the class, use security or just want to make sure that he user has to enter something valid as all of your checks can be done in the function before setting the private varible which can be easily canceled in the code.
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What is the difference between a field and a property?
(33 answers)
Closed 8 years ago.
Suppose I have a property in a class as in the following:
class testclass
{
public string Name {get; set;}
public void dosomething(){//...}
}
There is no functional difference between this format and the following:
class testclass
{
public string name;
public void dosomething(){//...}
}
Both name fields can be set to anything including an empty string and both can retrieve just without any restrictions. So what is the use of the property semantics detailed above where there is no validation or other process in the get and set methods? One use I see is that you can remove either the get or set method to make it write only or read only, respectively. I don't know what other use this would serve.
The main reason is so that you can change the implementation later without breaking client code. You might not do any validation or raise an event now but what if you decide to in the future? Also, properties can be bound while fields can't.
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What’s the difference between encapsulating a private member as a property and defining a property without a private member?
In C#, usually when I define a property I declare and implement a single line or more for get and set. e.g.
public bool IsThere
{
get { return _isThere; }
set { _isThere = value;}
}
now what does this mean?
public bool IsThere
{
get;
set;
}
Those are auto-properties. They work the same way as your first example, but allow you to omit the unnecessary source code.
They're best used when there is no longer to your getter/setter methods.
They also allow you to add logic to your getter/setter methods later without breaking any calling code (even though you'll also have to implement the private backing property yourself).
It's an Auto-Implemented Property (automatic property).
The C# compiler will automatically create a private field member for the get/set methods to read/write from.
Note that there are limitations to automatic properties (for now). For example, you cannot use modifiers such as readonly, though you can still mark it as private set it isn't quite the same.