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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).
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I've read the naming convention in https://learn.microsoft.com/en-us/dotnet/csharp/fundamentals/coding-style/coding-conventions.
However, I couldn't find the answer for this example below:
public class A
{
private int _b;
// Should I use "_" + camel case to name this member:
private string _c => _b.ToString();
// Or should I use pascal case to name this member:
private string C => b.ToString();
}
Should the member _c or C be called "private property" with a getter method or "private calculated field"? why?
If we want to use a member private internally with an expression body(=>) similar to this example. What is the naming convention for it?
As a common usage style in C#, fields start with a lowercase letter, properties start with a capital letter. Generally, fields begin with the _ character. If the data member is a field, it would be more appropriate to call it _c, and if it's a property, it would be called C.
Properties show fields. Fields are privately defined within a class and must be accessed via the get and set properties. Properties provide a level of abstraction that allows you to modify fields without affecting the external path accessed by clients using your class.
In this example, you don't need to define a field or property if you want clients to always use the _b variable as a string:
public class A
{
private int _b;
public string GetBAsString()
{
return _b.ToString();
}
}
References
What is the difference between a field and a property?
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An article about changes in C# 6.0 at Microsoft presents read-only auto-properties and claims (emphasis by myself):
An interesting consequence of support for auto-property initializers is that it eliminates many of the cases found in earlier versions where you needed explicit field declarations. (...) On the other hand, the need to declare read-only fields becomes virtually deprecated. Now, whenever a read-only field is declared, you can declare a read-only auto-property possibly as private, if that level of encapsulation is required.
Why in the world would I do that?
I fully understand the benefits of exposting properties rather than fields, as this maintains binary compatibility even in cases where I need to add some validation code or similar in a later version. But what is the benefit of always having a private read-only property over a private read-only field?
Please note that I am not asking about specific scenarios where a private read-only property has benefits over a private read-only field. The quoted article implies whenever a private read-only field could be used, one should opt for a private read-only property instead. Is there any tangible benefit from this, or was this just the author's enthusiasm about the new feature going overboard?
I replace the full context. This sentence is in the chapter Primary Contructors. With primary constructors, it make sense to replace read-only backing field by Auto-Property Initializers.
I agree, this sentence is weird :
Now, whenever a read-only field is declared, you can declare a read-only auto-property possibly as private, if that level of encapsulation is required.
When I read this, I see two axioms :
With primary constructor, you should use auto-property initializer instead of read-only backing field.
Hey guy, it's possibly to declare the property with auto initializer private
I think the author has favored brevity instead of readability or the author advocate to the end of field.
But the primary constructor isn't integrated in the final C#6 or next versions, so we still need backing field a long time.
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After reading a lot about immutability in C#, and understading it's benefits (no side effects, safe dictionary keys, multithreading...) a question has come to my mind:
Why there is not a keyword in C# for asserting that a class (or struct) is immutable? This keyword should check at compile time that there is no way you can mutate the class (or struct). For example:
public immutable class MyImmutableClass
{
public readonly string field;
public string field2; //This would be a compile time error
public readonly AnyMutableType field3; //This would be a compile time error
public string Prop { get; }
public string Prop2 { get; set; } //This would be a compile time error
public AnyMutableType Prop3 { get; } //This would be a compile time error
}
I think the compiler work would be quite easy, as it would need to check just a few things:
All public fields are readonly.
All public properties only have getters.
All public fields or properties have immutable types as well (simple value types, or immutable classes/structs).
All public functions or public property getters only depend on immutable fields or properties (public fields/props as described before, or private fields/props which comply to the same restrictions). This of course includes Equals(), GetHashCode() and ToString().
Some possible problems come to my mind with this design:
For the compiler to know that a compiled class/struct is immutable, it would probably be necesary to make changes in the intermediate language.
Readonly generic collection (such as IEnumerable<T>) immutability would depend on the immutability of the type <T>. The proposed immutable keyword would not be useful in this context, as you could not declare that IEnumerable<string> is immutable, even though it is.
Are the reasons stated before enough for this keyword to not exist?
Am I missing any other drawbacks?
Is this just not necessary enough for such big changes in the language?
The short version would be: because nobody has proposed, spec'd, designed, implemented, tested, documented, translated and supported that feature.
The longer version would relate to why to do it, given that it can be achieved indirectly with the readonly field - what benefit would it add.
For classes, it turns out to be relatively minor. Note that there is an [ImmutableObject(true)] attribute that can be used, but no features or frameworks really have a use for it, so ... nobody uses it.
There was a proposal to add "readonly structs" in a future version of C# (related to ref locals, Span<T>, etc) - but: it died a death and evaporated. However, the ref readonly stuff lives on, which is intended to prevent reassignment of this in struct instance methods.
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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I am confused on how to create class can you please help me??
class AutomotiveManager
{
private bool isBeingTested
{
set
{
isBeingTested= false;
}
}
private dialogResult MessageBoxResult
{
///need help over here
}
}
It seems that there are a few different issues here.
The difference between properties and attributes
The meaning of the = in the attributes
The error (which error?) you get for the declaration of the messageBoxResult
Private Attributes are just private Attributes.
So the implementation of a private attribute like the isBeingTested would be
private bool isBeingTested;
The = in the attributes means the default value. So that would be the value you assign in the constructor or at the declaration of the attribute. For the isBeingTested you could add that to the declaration like this:
private bool isBeingTested = false;
But since in C# the default value for a boolean is false anyway you don't even need to specify it. The way you programmed it you will en up in an infinite loop the moment you try to use the setter for isBeingTested
The «Property» presumably indicates that you are meant to create a Property rather then an Attribute, and I guess the {get;} indicates that you only need to implement a getter, not a setter for this property. (I'm guessing here since none of that is defined in UML)
The error you are getting is probably because the compiler doesn't know the type dialogResult. It may know the type DialogResult (notice the uppercase) if you add System.Windows.Forms as a reference to your project, and add a using statement like this
using System.Windows.Forms;
PS. You also failed to implement the static keyword on the class.
To convert your UML class diagram into a C# class, you'll need to understand what each of the symbols represent in your UML class diagram. This image from tutorialspoint.com is useful:
From there, it's a matter of writing the equivalent C# code based on the symbols provided in your example.