Ok this is bugging me.. I know I've read it somewhere and google isn't helping.
What is the accessibility level of a method that does not specify an access modifier?
void Foo()
{
//code
}
I want to say internal but I'm not 100% sure.
The default accessibility for a type is internal, but the default accesibility of that type's members depends on the type.
Generally speaking, members of a class are private by default, where as members of a struct are public by default. This varies by language; default struct access modifiers for C++ are public, where as for C#, they are private.
Assuming this is a C# method, since you have the ".net" tag.
People need to differentiate between "member" accessibility and "class" accessibility.
The default accessibility of class members (including methods) in C# is private. See https://msdn.microsoft.com/en-us/library/ba0a1yw2(v=vs.140).aspx
The default accessibility of a class itself is internal.
Yes, internal is the default for classes, but private is the default for members.
For a class: Internal is the default if no access modifier is specified.
For a method: Private is the default if no access modifier is specified.
From The C# Programming Language, Third Edition by Anders Hejlsberg et al, section 10.3.5 ("Class Members - Access Modifiers") on page 434:
A class-member-declaration can have any one of the five possible kinds of declared accessibility (§3.5.1): public, protected internal, protected, internal, or private. Except for the protected internal combination, it is a compile-time error to specify more than one access modifier. When a class-member-declaration does not include any access modifiers, private is assumed. [Emphasis mine]
And then in section 11.2 ("Struct Members") on page 539:
Except for the differences noted in §11.3, the descriptions of class members provided in §10.3 through §10.14 apply to struct members as well.
Section 11.3 does not mention anything about access modifiers, so my reading of this implies that members of a struct without an access modifier are also private by default. This corresponds with what MSDN says and with my own experience.
Oh wait, there's one more thing ....
interface method declarations are of course public by definition. So the following implementation is public, without an explicit access modifier.
public class MyClass : IEqualityComparer<MyClass>
bool IEqualityComparer<MyClass>.Equals(MyClass x , MyClass y) {}
}
hope this clarifies all as per screenshot directly from MSDN
Class methods are private and sealed by default in .NET.
This means the method is only visible within the class and cannot be overridden by the inherited class.
Related
The default access modifier for an interface is public. However,
in C# can we ever use protected access modifier for an interface?
In this example:
class C
{
protected interface I
{
}
}
the nested type I is protected.
This means that I is visible to all of C and also to all classes that derive from C. For example this could be used to make protected instance methods inside C that contain I in their signatures or return types.
Note: The default accessibility for an interface is not public, like you claim. The default accessibility for a member of an interface is public. That is something else.
The default accessibility for the interface itself depends on what the interface itself is a member of. If the interface is a member of an "outer" class or struct (like my C above), it has the usual default accessibility of class and struct members, which is private. If the interface is a direct member of a namespace (possibly the global namespace), the default accessibility is the usual default for all non-nested types, which is internal.
You can change this acceccibility.
See this page : https://msdn.microsoft.com/en-us/library/ms173121.aspx.
It's say that "Interfaces declared directly within a namespace can be declared as public or internal and, just like classes and structs, interfaces default to internal access."
Be carefull, as you see in this link https://msdn.microsoft.com/en-us/library/ba0a1yw2.aspx members are public by default and can't be modified.
I'm building a DLL with some basic functions. Long story short, I'm making a few static classes for the use by devs. These classes use some other classes that do the dirty work, which I marked as internal because I don't want people to access them.
The question is: If I declare a class as internal, what the access level of his members will be?
I'll have to mark as internal all of its members or they are automatically labeled as internal too?
It's a good 2 hours I'm googling and searching in stackoverflow and I'm struggling to find a clear and straight answer which doesn't include 1000 speculations, technical not-so-probable hypotesis and useless decorations...
MSDN is confusing as usual (never found a clear answer on msdn).
From what I can read here http://msdn.microsoft.com/en-us/library/ms173121.aspx I guess that no matter how you set a class access level, all his members will be private (methods, variables and so on).
Help, I don't know
The question is: If I declare a class as internal, what the access
level of his members will be?
The default will be private. If anything else, then it depends. If they are anything other than public, then the access modifier applies as described on MSDN (e.g. not visible outside of the assembly).
However, in the link you posted, there is one gotcha which applies to non-static classes:
Normally, the accessibility of a member is not greater than the
accessibility of the type that contains it. However, a public member
of an internal class might be accessible from outside the assembly if
the member implements interface methods or overrides virtual methods
that are defined in a public base class.
In relation to the last paragraph, since static classes cannot implement interfaces or inherit other classes then you can rest assured. As long you declare your static class internal, the members will not be available in other assemblies (unless your devs use reflection).
To exemplify how it does work for non-static classes:
Assembly 1
public interface ISomePublicInterface
{
int GetValue();
}
internal class InternalClass : ISomePublicInterface
{
public int GetValue()
{
return 100;
}
}
public static class SomeFactory
{
public static ISomePublicInterface GetInternalInstanceAsInterface()
{
return new InternalClass();
}
}
Assembly 2
ISomePublicInterface val = SomeFactory.GetInternalInstanceAsInterface();
Console.WriteLine(val.GetValue()); //-->> Calls public method in internal class
Console.WriteLine(val.GetType());
Guess what the output is?
Assembly1.InternalClass
So, now you have access to the type outside of the assembly and via reflection someone could call other internal methods (it's not the only way to get it).
From MSDN only
The access level for class members and struct members, including
nested classes and structs, is private by default.
interfaces default to internal access.
Hope this table helps:
Members of Default member accessibility
---------- ----------------------------
enum public
class private
interface public
struct private
Also check this MSDN
Private unless otherwise stated. However, public will have same result as internal.
If you later promote a class from internal to public, then creating public class objects will become visible, whilst internally scoped methods will stay internal.
You might want to consider behaviour in case your class scope gets updated.
Another stack overflow question.
If u Declare any class as "internal" then its means you can access this class in same assembly. But what kind of access specifier you use for class member is decide they are accessible are not in different class in same assembly.
All the members of internal class would be internal and will be accessible with in the same assembly and will not be outside neither class nor members.
If you want to access class in other assemblies, make the class public and member you don't want to be accessed outside assembly make them internal.
If I declare a class as internal, why does the IL show it as private?
internal class Thing
.class private auto ansi beforefieldinit Thing.Thing
extends [mscorlib]System.Object
From IL's point of view, private means private to the assembly, i.e. internal in C#.
In C#, it is not possible to mark types as private if they are not nested. IL's equivalent accessibility for such types is nested private.
So we have:
C#'s internal -> IL's private (to the assembly)
C#'s private -> IL's nested private (to the enclosing type)
On MSDN, it says:
The C# keywords protected and internal have no meaning in IL and are
not used in the reflection APIs. The corresponding terms in IL are
Family and Assembly. To identify an internal method using reflection,
use the IsAssembly property. To identify a protected internal method,
use the IsFamilyOrAssembly.
So I guess it just makes them private, since they can't be accessed from elsewhere.
EDIT: I see how my answer might not be completely correct, I just thought it was something worth noting. The MSDN article I linked has some interesting stuff on this "what code we write" - "what it becomes" relationship.
The mapping of C# keywords to IL keywords isn't always a logical one. Ecma-335, section II.23.1.15 shows what flags are valid for a type. You'll see that it only defines Public, NotPublic and a set of NestedXxx flags. Nothing similar to "internal". So your class is actually NotPublic, displayed as "private" in ildasm.
It is easy to see a side-effect of this: try this declaration in your C# code:
private class DoesNotWork {
}
You'll get:
error CS1527: Elements defined in a namespace cannot be explicitly declared as private, protected, or protected internal
If I have a method that does not specify its Accessibility Level will it be Private by default?
void Item_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
throw new NotImplementedException();
}
Is the above method private?
It is. The general rule if you don't define any modifier is "the most restricted modifier that can be applied here is used", so private for methods, internal for top-level classes, etc.
Yes, it is private.
For a method inside a class, default is private. It does vary based on the scope of where things are declared, here's an MSDN link with more specifics
Yes, for methods, like your example.
Class and struct members, including nested classes and structs, have
private access by default.
But that is not correct for all the access modifiers:
Classes, records, and structs declared directly within a namespace (in
other words, that aren't nested within other classes or structs) can
be either public or internal. internal is the default if no access
modifier is specified.
I consider this a good idea, because by default in OO, everything should be private and only what is really needed should be marked public.
https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
What are the access-specifiers available in c#? What is the default one?
The possible access modifiers are :
private
protected
internal
protected internal
public
The default modifier that is used, depends on the element.
For classes, the default specifier is
'internal'
For class-members, the default
specifier is private
For nested types (inner classes), the
default is private
You can also find it on MSDN
You might find it also interesting to have a look at this
A copy of the C# Language Specification is included when you install Visual Studio (in 2008 at least), at VSRoot\VC#\Specifications\1033\CSharp Language Specification.doc. This is, of course, the definitive place to look.
Access Modifiers (Access Specifiers) describes as the scope of accessibility of an Object and its members. All C# types and type members have an accessibility level . We can control the scope of the member object of a class using access specifiers. We are using access modifiers for providing security of our applications. When we specify the accessibility of a type or member we have to declare it by using any of the access modifiers provided by CSharp language.
C# provide five access specifiers , they are as follows :
public, private , protected , internal and protected internal .
public :
public is the most common access specifier in C# . It can be access from anywhere, that means there is no restriction on accessibility. The scope of the accessibility is inside class as well as outside. The type or member can be accessed by any other code in the same assembly or another assembly that references it.
private :
The scope of the accessibility is limited only inside the classes or struct in which they are declared. The private members cannot be accessed outside the class and it is the least permissive access level.
protected :
The scope of accessibility is limited within the class or struct and the class derived (Inherited )from this class.
internal :
The internal access modifiers can access within the program that contain its declarations and also access within the same assembly level but not from another assembly.
protected internal :
Protected internal is the same access levels of both protected and internal. It can access anywhere in the same assembly and in the same class also the classes inherited from the same class .