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I have proved to myself that the namespace is not required to compile and run an application. However, what are the dangers and pitfalls of not using a namespace? It creates layers that I am trying to avoid.
I know you're screaming but what about agile and abstraction so that 20 layers of abstraction exist between the code and the object. I'm not asking if it violates this or that flavor of the month agile thing. Just what, if any, real world issues come about by not using a namespace?
Edit:
Creating a stand alone class dll so no conflicts within the class project. Trying to avoid when I include it in other projects having to use full qualified name. myNamespace.myClass MyClass = new myNamespace.myClass();
From the comments it appears that naming conflicts are the biggest problem.
Guess I should use a using statement and buck up...
Namespaces have two principle uses:
First, they enable the consumers of your code to more easily understand, find and correctly use your code. There is a reason why the system diagnostic tools are in System.Diagnostics namespace. It's so that customers can know what the stuff in there is for.
Second, they are a mechanism for preventing name conflicts.
The first is actually by far the more important. Conflicts aren't that common. Still, they are possible and judicious use of namespaces prevents them.
If you don't care about your customers finding, understanding and using your code, and you don't have naming conflicts, then sure, skip using namespaces.
It creates layers that I am trying to avoid.
There are no real additional "layers" created. The namespaces purely allow a way for the types to be organized, and help prevent naming collisions as projects get larger and more libraries are used.
As far as the runtime is concerned, there are no namespaces - all types are fully qualified, and the namespace in C# just changes the type name. Leaving the namespace off just makes your type name more likely to conflict with other names, but will have no "real impact" on whether or not the code works, provided you don't use the same name more than once in your project, or use a name that's the same as a name of a type from a referenced assembly and imported via using.
Edit in response to comment:
What I mean by "it creates layers" is that when I create the object I have to add the namespace as a layer. (i.e. myNamespace.myClass MyClass = new myNamespace.myClass();) "
Note that this is only required if you don't have a using myNamespace; statement, or if you use multiple namespaces within the project. If you're always working within the project's default namespace, then you will not need to qualify the name.
It might be a good idea to compare what life without namespaces looks like. The C language does not support namespaces. And very early in its existence, the open() function was used to open files.
Which means that no C programmer may ever use the name "open" for their own function.
Painful isn't it?
Namespaces help you use short and descriptive names. They do not add layers, they only create longer names. That you can very easily write shorter, the using directive makes it easy.
You can end up with conflicts and isn't standard practice for C#. It won't truly hurt anything in the long run.
A conflict could arise if you named your class the same thing as another visible class. For instance, if you named your class Math and had a using System; using statement, there would be a conflict that would only be resolved by specifying System.Math.
Again, not the norm and not something that should be published outside of internal use, but it sounds like you already know that :)
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I knew it is recommended to use different names in class and namespace, but sometimes it is hard to achieve it. It is easier said than done. They never give us a solution when we need to use the same name because of a certain case.
For example, I need a namespace in which to locate all the classes about configuration, so the namespace is named ABC.Configuration. I don't think there is anything wrong with this name.
And under the namespace I need a class to store the configuration, so its name will also be Configuration. Reasonable, don't you think?
Besides I have some other classes such as ConfigurationBuilder, ConfigurationManager, etc, under the namespace.
What's more in Java, the package name we use "camelCase", and the class name we use "PascalCase". So because of the case of naming, there is no problem.
So how to name the classes in this scenario in C#？
Thank you very much. If I use Configuration.Configuration, I need to write more only because of naming while others are just ConfigurationManager without the namespace. It's a little bit mess.
The idea to use ConfigurationStore is a good one, thank you.
I think the solution to name a class is to identify the usage clearly in the name and add another word.
But in my project, I need to use the Configuration somewhere, if I write ConfigurationStore.Path to read the configuration, it looks strange.
Maybe I can use a interface like IConfiguration to avoid the naming problem
You could name your namespace ConfigurationManagement. Or name your class ConfigurationStore if it stores configurations.
camelCase vs PascalCase: The same tools that tell you naming your namespace like a class is bad, will tell you that entities who's name differs only in capitalization are bad, too.
So find better names.
It's perfectly ok to use the same name for the namespace and class. You can refer to your Configuration class as Configuration.Configuration or Configuration if you have a using directive. There is no confusion.
If it is just your personal preference that you don't like to have a class with the same name as the namespace, here are some other names for configuration:
Config
Configurations
Configs
ConfigurationManager (class name only)
Also, IDEs will probably tell you what an identifier refers to by having different icons. For example in Xamarin Studio:
Namespaces are marked with {s while classes are marked with Cs.
In C# PascalCase is used in both scenarios. For namespaces and for classes if I'm not wrong about it.
Why have ABC.Configuration when you can just have ABC? I mean, it will be a bit confusing not to mention long names. ABC.Configuration.Configuration, to access the Configuration class, as opposed to ABC.Configuration. I would rather apply the latter.
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For example, I name my file(console application) 'Hello', so do I have to write namespace Hello?If no, what is the purpose of adding namespace?
No, the namespace can be anything, they don't have to be the same as the filename. It is good practice to have the namespaces correspond to physical file paths (folders in your solution).
So if you have a file in .\Interfaces\ViewModels\Client, usually the namespace declaration in that file will be:
namespace DefaultNamespaceOfAssembly.Interfaces.ViewModels.Client { ... }
ReSharper even offers to fix up namespaces that are breaking this rule.
The purpose of the namespace is to
modularize your code by putting things that belong together (by functionality for example) in the same namespace,
reduce name collisions. Without namespaces importing an external library would result in hell if it were to contain classes with the same name as classes in your own code.
Probably there are more, but at first thought these come to mind, although these two should already be enough to justify their existance.
I name my file(console application) 'Hello', so do I have to write namespace Hello?
No, you can name it whatever you want.
If you're writing a library to be used by other code, and that library is the only (or main) source of types in that namespace, then it would be convenient to users for the DLL to have a name based on the namespace, because then they can easily remember that the UsefulTypes.CoolStuff classes all come from the UsefulTypes.CoolStuff.dll assembly. There's no rule that you have to do this, it can just be convenient if you do.
With applications this isn't anywhere near as useful; end-users don't care what namespaces you use and may not know what a namespace is. It might be useful if the application was a tool for .Net developers, but otherwise not.
If no, what is the purpose of adding namespace?
Exactly what it says; it's a space for names. By putting the names of classes, enums, delegates and structs into a namespace they are separated from other cases of the same name being used in other namespaces. You don't have to make sure that no library you used has something with the same name, unless you are actually going to use that thing with the same name.
When writing an application it keeps stuff from other assemblies out of your way. When writing libraries it's even more important, as it also keeps your stuff out of other people's way.
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Consider for the question this String.Split overload, which takes a StringSplitOptions enum as a parameter.
Isn't it bad that the enum itself is public and accessible to everything that includes the System namespace? I mean, the enum is completely specific to options of the Split method, yet it's available outside of it's scope.
Perhaps there is a better way to model this, like putting the enum inside the String class itself, and accessing it by using String.SplitOptions for instance? I very rarely see this (I actually can't remember any such case now), so I assume it is not preferred for some reason. In general, I think reducing the scope of things is a best practice because you lower the chance of problems occurring by using a class/member in an incorrect scope, so to speak.
I'm using Split as an example here, but it is quite common for a Enum to be used only by a method or class in our code base too. I generally create the enum as a public type in a separate cs file like any other class, but I would love to hear other approaches to this 'problem'.
Update:
I just found this article that attacks this exact problem, with a Folder class and a Filter enum but again seems go against what I believe would be more correct in that case (placing the enum inside the class somehow). One of the comments in there from ToddM (which I happen to agree with) states:
...
But, even then, I feel your logic is wrong. Your main complaint
against embedding the enum inside of the class is that it will take
too long to type. Given how verbose C# tends to be, this is not really
a sensible argument. In VS, CTRL+SPACE is your friend.
Logically, I feel placing the enum inside of the class is far more
correct. Take your example: what is a MyNameSpace.Filter? Where does
it apply? I guess it's a filter for your namespace? It's impossible to
tell, especially if your namespace grows to contain dozens of classes.
Now consider MyNameSpace.Folder.Filter -- it is, in my mind, far more
intuitive that Filter applies in some way, shape, or form to the
Folder class. Indeed, another class can be added to the namespace with
its own concept of filter, one of whose members may be 'File'. Just
because you've introduced a new class into the namespace doesn't give
you the right to pollute that namespace with various 'helper' types.
If you are developing as part of a large development team, your style
is, well, rude.
...
It's an interesting idea to nest the enum in order to suggest that it has a reduced scope, or to give it better semantics. I have used this idea before in order to have both error codes and warning codes in a post-compiler I developed. This way, I could use the same enum name Code nested either in the Error class or the Warning class.
On the other hand, public nested types are generally discouraged. They can be confusing to clients who have to qualify them with the outer class name. Look at the related guidelines on MSDN. Some that are relevant:
DO NOT use public nested types as a logical grouping construct; use namespaces for this.
AVOID publicly exposed nested types. The only exception to this is if variables of the nested type need to be declared only in rare scenarios such as subclassing or other advanced customization scenarios.
DO NOT use nested types if the type is likely to be referenced outside of the containing type.
For example, an enum passed to a method defined on a class should not be defined as a nested type in the class.
I believe those guidelines were followed when developing the StringSplitOptions enum, and most of the others in the BCL.
String.Split() is public, so StringSplitOptions has to be public too. Both String and StringSplitOptions exist in the System namespace. Both have public scope. Neither is "available outside of [the other's] scope".
I think one of the reasons is that it would make every call using an embedded enum wider (the name of the class becomes a mandatory prefix).
I personally wouln't appreciate having to use ResultSetTransformer.ResultSetTransformerOptions every time I have to use this enum, it would make my line horribly long.
But as others pointed out, I don't think it's standard in the framework to embed enums in classes at all, possibly for this reason.
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Placing custom code in a System namespace
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Closed 8 years ago.
I have a class called ConfigurationElementCollection<T>
It's a generic implementation of System.Configuration.ConfigurationElementCollection
It's stored in our solutions', Project.Utility.dll but I've defined it as being part of the System.Configuration namespace
namespace System.Configuration
{
[ConfigurationCollection(typeof(ConfigurationElement))]
public class ConfigurationElementCollection<T> :
ConfigurationElementCollection where T : ConfigurationElement, new()
{
...
}
}
Is putting classes in the System.* namespaces considered bad practice when they aren't part of the System.* Base Class Libraries ?
On the face of it, it seems to make sense, as it keeps similar classes with similar functionality in the same place. However it could cause confusion for someone who didn't realise it was actually part of a non .net BCL as they wouldn't know where to go hunting for the reference.
While your class is similar it is still not part of the BCL. I would not put it in System.* because of this. It will cause confusion especially when one goes to use it and they have System.* referenced and then get a nasty can't find message when they go to use your class.... :-)
I'd recommend either replacing System by your company/project name or prefixing the namespace with your company/project name.
That way you make it clear that it's not part of the BCL, but exactly how it's related to them.
Also in the (admittedly unlikely) event Microsoft ever implement these classes/methods with exactly the same names you won't get a clash.
I was wondering, what the purpose of Namespaces in C# and other programming languages is...
As far as I know, they are used for two things:
To structure the project into meaningful pieces
To distinguish classes with the same name
My Question is: Are there any other things to consider when using namespaces? Do they have an impact on performance or something like that?
As far as I know, they are used for two things:
• To structure the project into meaningful pieces
• To distinguish classes with the same name
That's basically it. I would add to your first point that namespaces provide structure larger than just that of the project, since namespaces may span projects and assemblies. I would add to your second point that the primary purpose of namespaces is to add structure to libraries so that it becomes easier to find stuff you need and avoid stuff you do not need. That is, namespaces are there as a convenience for the user of a library, not for the convenience of its creators.
A secondary purpose is to disambiguate name collisions. Name collisions are in practice quite rare. (If the primary purpose of namespaces was to disambiguate collisions then one imagines there would be a lot fewer namespaces in the base class libraries!)
Are there any other things to consider when using namespaces?
Yes. There are numerous aspects to correct usage of namespaces. For example:
violating standard naming conventions can cause confusion. In particular, do not name a class the same as its namespace! (See link below for details.)
using a namespace can bring extension methods into play that you didn't expect; be careful
where precisely the "using" directive goes can subtly change resolution rules in a world where there are name collisions; these situations are rare, but confusing when they arise
collisions often arise in contexts where machine-generated code is interacting with human-generated code; be careful in such situations, particularly if you are the one writing the code generator. Be very defensive; you don't know what crazy name collisions the person writing the human-generated half is going to create.
See my articles on this subject for more details:
http://blogs.msdn.com/b/ericlippert/archive/tags/namespaces/
And see also the Framework Design Guidelines for more thoughts on correct and incorrect conventions for namespace usage.
Do they have an impact on performance or something like that?
Almost never. Namespaces are a fiction of the C# language; the underlying type system does not have "namespaces". When you say
using System;
...
class MyException : Exception
...
there is no class named "Exception". The class name is "System.Exception" -- the name has a period in it. The CLR, reflection, and the C# language all conspire to make you believe that the class is named "Exception" and it is in the namespace "System", but really there is no such beast as a namespace once you get behind the scenes. It's just a convention that you can sometimes omit the "System." from the name "System.Exception".
According to MSDN a namespace has the following properties:
They organize large code projects.
They are delimited with the . operator.
The using directive means you do not need to specify the name of the namespace for every class.
The global namespace is the »root« namespace: global::System will always refer to the .NET Framework namespace System.
Secondly namespace has nothing to do with performance but if you have created your own namespace so you should follow the conventions across the project.
It doesn't affect performance. But for code readability, I would recommended remove unwanted using statements
Namespaces are a concept pulled from earlier technology, like XML. THe namespace gives context to your classes, allowing you to have say a CUstomer object in your domain and in your data code.
You can also use namespaces to alias, which still does the above, but allows shorter naming for the particular object.
domain.customer
versus
data.customer
You've touched upon the two main reasons. This is an old article from MSDN but it still applies: Namespace Naming Guidelines
In the Java world the naming practice is to reverse the domain name of the company who owns the product and include the product's name after that. So com.example.product might be a valid namespace, but you don't really see that in .NET so much.
Those are the big ones right there.
There aren't really performance benefits. At least, not directly. without namespaces framework would have to search the a lot more places to find the code you are trying to include - It would almost be like needing to load up the ENTIRE .NET framework for every project. Well, not really, but its close enough for this discussion.