I'm trying to group together MANY helper classes into a common parent class for ease of use. For example, in my applications I want to do
Tools.StringTool.foo(..)
Tools.NumberTool.bar(..)
Tools.NetworkTool.something(...)
The idea here is to organize all the tools under a common Tools class so that intellisense can bring them all up when I type "Tools.".
Defining all the tools under a parent static partial class Tools works fine but not for Tools in a different assembly.
I tried to emulate static partial classes across assemblies by replacing the parent Tools class with a namespace X.Y.Tools, but for code written outside X.Y namespace, I need to fully qualify each tool before using it.
i.e. in app code
Tools.MyTool(..) // won't compile
X.Y.Tools.MyTool(...) // will compile but ugly
Any suggestions how I can solve this issue or alternative approaches for organizing the tools?
You can use extension methods in this case. All extension methods defined in classes within a namespace are made available when that namespace is imported.
This way you'd have static classes like MyUtilityNamespace.MyClassInAssembly1 and MyUtilityNamespace.MyClassInAssembly2 that all provide extension methods onto a single class instance, but this has ugliness associated with getting that class instance, like so:
// in central assembly
class Tool {
private static Tool _t = new Tool();
public static Tool T { get { return _t; } }
}
// in utility assembly 1
public static class MyExtensionClassInAssembly1 {
public static void SomeUtilityMethodX(this Tool tool, Object arg1, Object arg2) {
// do something
}
}
// in utility assembly 2
public static class MyExtensionClassInAssembly2 {
public static void SomeUtilityMethodY(this Tool tool) {
// do something
}
}
You'd use it like so:
Tool.T.SomeUtilityMethodX( Tool.T.SomeUtilityMethodY(), null );
it isn't pretty, but means you only need to import an namespace once, and the Tool.T is constant, there's no need to memorize StringTool or NetworkTool.
Another alternative is to use namespace or type aliasing, however this is laborious as you need to specify the using Tools = X.Y.Tools.MyTool; line on every source file you have.
Turns out the easiest way to do this is simply use namespaces
// in project 1
namespace Tools {
public static class NetworkTool {
}
}
// in project 2
namespace Tools {
public static class FileTool {
}
}
// in client code (references both projects)
Tools.NetworkTool.SomeMethod();
Tools.FileTool.SomeMethod()
Related
After attempting to research C# namespaces further (coming from a c++ background) I think I understand the purpose of namespaces in general - to organise classes for the user, and to avoid conflicts. This practise, I imagine, still holds just as true for programs as it does for libraries.
What I don't understand is why exactly classes housing the Main() function would need to be part of a namespace.
I can't imagine that the main function would need to be called elsewhere for any reason, so organisation and conflict prevention ought not to be the reason.
Is it simply to show other developers what namespace to use throughout the rest of the program's classes? Or is there some deeper reason for it that is going over my head?
What I don't understand is why exactly classes housing the Main() function would need to be part of a namespace.
For sake of simplicity, we're going to assume that the class that contains Main() is called Program.
The Program class does not need to be in a namespace. For example, explicitly declaring the class:
// Program.cs
public class Program {
public static void Main(string[] args) {
System.Console.WriteLine("hi");
}
}
namespace MyNamespace {
public class Data {
public int Val {get;set;}
}
}
or using Top Level Statements
// Program.cs
System.Console.WriteLine("hi");
namespace MyNamespace {
public class Data {
public int Val {get;set;}
}
}
SharpLab (the links above) shows you what the compiler will output, and in both the Program class doesn't exist inside a namespace, even though other classes will.
And for the record, this is not limited to the Program class. You can put any/all of your types in the "global" namespace. You just lose the "categorization" benefit of namespaces.
I can't imagine that the main function would need to be called elsewhere for any reason
I'd agree. Normally you'd let the .Net runtime call your Main method. I'm sure you can think of some reason to do so, but really that's up to the architecture of your application. One maybe valid use case would be automated testing with a testing framework (xUnit, MSTest, etc) in a sibling assembly.
Now, say you did want to call the Main method yourself, as long as the Fully Qualified Type doesn't conflict with something else, you can still call it just like normal.
public class Program
{
public static void DoThing() { }
}
namespace MyNamespace
{
public class Data
{
public void ActivateDoThing() => Program.DoThing();
// or, if you run into a conflict
public void ActivateDoThing() => global::Program.DoThing();
}
}
Is there a reason for giving the class holding Main() a namespace in C#?
This is due to the editor you're using. Except for the Top Level Statements feature, when you create a new project with the "Console Application" template, it will have the Program class wrapped in a namespace, which is consistent with creating a new code file for a new class. This is just a decision the authors of the template have chosen, but at least it does follow the rule that every file has a namespace block. Familiarity can enhance readability, even if its inefficient.
That's really the point of the Top Level Statements feature - get rid of all the boilerplate. Technically, you don't need a namespace for the entry point class - so get rid of it. Most of the time, you don't add anything to Program besides the Main method, so don't require the user typing the class or method signatures. Just let the user get to the Main logic as fast as possible and the compiler can generate the rest.
That's really about it. Why is the namespace there? Mostly for consistency. Does it need to be there? Nope, not at all.
I'm working on a large API project that needs to release 2 DLLs with many interfaces written in C++/CLI (one DLL contains interfaces for public use and the other extends some of the public interfaces for internal company use only).
All implementation classes for all interfaces are in a separate project and are all contained in a separate DLL as well.
Most internal interfaces usually just extend the public version by one by 1 or 2 methods, I opted to reuse the same implementation classes for code reuse.
Here's an example:
//Company.PublicInterfaces.dll
namespace Company
{
namespace PublicInterfaces
{
//contains public properties, methods, etc that any developer can use
public interface class ICompanyProduct
{
void GetProductInfo();
//...etc
}
public interface class IOtherStuff
{
void GetOtherStuff();
}
//...plus many more interface definitions
}
}
//Company.InternalInterfaces.dll
namespace Company
{
namespace InternalInterfaces
{
//extends the public interface to include secret methods that only company developers can use
public interface class ICompanyProductInternal : ICompanyProduct
{
void GetSecretInfo();
//...etc
}
//...plus many more interface definitions
}
}
//Company.InterfaceImplementations.dll
#include "Company.InternalInterfaces.h"
namespace Company
{
namespace InterfaceImplementations
{
public ref class CompanyProductImplementer : ICompanyProduct, ICompanyProductInternal
{
//implements both interfaces
}
public ref class OtherStuffImplementer : IOtherStuff
{
//implement other stuff
}
//...plus many more interface implementations
}
}
//C# Test App
using Company.InternalInterfaces
using Company.PublicInterfaces
using Company.InterfaceImplementations
namespace TestApp
{
class TestAppProgram
{
static void Main()
{
//write code that uses both interfaces for reusability or for whatever reason....
ICompanyProductInternal internalProduct = new CompanyProductImplementer();
IOtherStuff otherStuff = new OtherStuffImplementer();
}
}
}
The Company.InternalInterfaces project references the Company.PublicInterfaces project.
Since we can't ship Company.InternalInterfaces.dll, the Company.InterfacesImplementation project can only reference Company.PublicInterfaces or we risk exposing the internal interfaces.
But since class CompanyProductImplementer also implements ICompanyProductInternal, I had to include "Company.InternaInterfaces.h".
When building the C# test app, Visual Studio 2013 complains of
Error: The type 'Company.InternalInterfacs.ICompanyProduct' exists in both 'Company.InterfacesImplementation.dll' and 'Company.InternalInterfaces.dll'
The only way it works is if the implementation project also references the internal interface project, but that's not possible because I'll have to ship the internal interface library as well.
How can I solve this? Obviously this is a typical scenario with regards to many companies wanting to reuse their code for public and internal use in large projects.
As I see Company.InternalInterfaces.dll and Company.PublicInterfaces.dll are only interface dlls for the same Company.InterfaceImplementations.dll where all logic implemented. Such configuration typically used when you don't need to hide functionality, but because of usability reasons. In this configuration anyone could access Company.InterfaceImplementations.dll code logic via decompilation and execute any code via reflection.
To hide internal logic you could extract Company.Base.dll with common services used by everyone and split other code from Company.InterfaceImplementations.dll into internal Company.Internal.dll and public Company.Public.dll. In such case you need to distribute Company.Base.dll and Company.Internal.dll or Company.Base.dll and Company.Public.dll.
The other option is to create two build configurations PublicAPI and InternalAPI for Company.InterfaceImplementations.dll. In different configurations, different #define directive should be used. In this case code logic could be included or excluded based on this #define. It will give you ability to exclude internal logic from public dlls.
Error: The type 'Company.InternalInterfacs.ICompanyProduct' exists in both 'Company.InterfacesImplementation.dll' and 'Company.InternalInterfaces.dll'
Any way you should split your code properly to prevent duplicate definitions of the same interfaces in several dlls. Place it in only one dll, e.g. Company.Base.dll.
To properly consumes C++-CLI types defined in other assembles you should use using. E.g:
using "Company.InternalInterfaces.dll"
instead of
#include "Company.InternalInterfaces.h"
in your Company.InterfaceImplementations.dll assembly. Useful C++-CLI article "How to: Define and Consume Classes and Structs".
I recently branched out into C# written with Visual Studio Express from C++ written with gVIM. I've been told I'll have to unlearn a lot of stuff to really use C# effectively, but here's my question:
In C++ when writing a class or data type, I would have separate files for the class definition and the driver program. I would then #include the class in the driver program in order to use it. It isn't terribly clear how to do this in Visual Studio Express 2013 and all the tutorials I've looked up have the class definition and the Main() routine in the same file.
I currently have only two files in my solution folder: the driver program p1.cs and the type definition/implementation targetInt.cs. What is the best way to allow p1.cs to work with my targetInt.cs type? Will it simply have access by virtue of being part of the same solution? If so, how to I get around not having a Main() routine in my type definition?
Here is a screenshot of the solution and the error I'm getting when I try to build the solution. I don't get an error for trying to declare a targetInt object in p1.cs which points to the namespace already being shared.
http://i793.photobucket.com/albums/yy218/tombombodil/solution_zps6a743e2d.png
Let me know if I need to clarify anything.
It's really not terribly complicated, but it is different from C++. So if you have one file that looks something like this:
namespace MyNamespace
{
public class MyClass
{
//...stuff
}
}
And then you want another file with your Main (which you will for anything more than a trivially simple project), it would look something like this:
using MyNamespace; // unless you use the same namespace for both
namespace SomeOtherNamespace
{
class Program
{
static void Main(string[] args)
{
var c = new MyClass();
// alternatively, without the using statement, you can just fully qualify
// your class name like so:
// var c = new MyNamespace.MyClass();
}
}
}
But do note that the files need to be in the same project. If they are in different projects you can still do it, but you have to add a reference to the project with MyClass to the project with Program. What you can't do is just have an orphaned C# file floating around in your solution and expect it to work.
The problem as you've written boils down to the simple lack of shared namespaces - because targetInit exists in a separate namespace, Program needs a using targetInit.cs to access the targetInit type. They can, however, access each other by virtue of being in the same project - a Solution can contain multiple Projects, and if they don't reference each other, they can't access each other's types.
Usually, the naemspace of any given class is actually the folder path to it, and the class name is the same as the file name (which Visual Studio does for you when you make new class files).
As for the Main() definition, you only want one of these since you only have a single entry point for the system to jump to when your program begins - having multiple Main() functions doesn't make much sense when the OS needs a clear place to begin execution.
The Main() method and class definitions sitting in the same file is a convenience so all the code can be read together - to get an idea for how actual projects are set up, trying going to GitHub and forking a couple of open-source projects.
there are two approaches to use another class in C# directly:
1-putting that class in the same namespace of my class(even if they were in separate files), this code clarify this:
//file TargetInt.cs
namespace MyNameSpace
{
class TargetInt
{
}
}
//file p1.cs
namespace MyNameSpace
{
class p1
{
static void Main(string[] args)
{
}
}
}
notice that both classes are in MyNameSpace namespace.
2-if the other class is contained within another namespace, you can simply use it by declaring this statement in the upper beginning of the file:
//file TargetInt.cs
namespace OtherNameSpace
{
class TargetInt
{
}
}
//file p1.cs
using OtherNameSpace;
namespace MyNameSpace
{
class p1
{
static void Main(string[] args)
{
}
}
}
with using OtherNameSpace; you can use TargetInt class directly.
I want to build a Windows Store class library using source code from a regular .NET Framework class library. Ideally, I do not want to modify the original source code files.
In some of the source code files from the .NET Framework library, static members are used from a class that is defined in both the regular .NET Framework API and the .NET for Windows Store apps API, but where only a subset of the .NET Framework members are available for Windows Store.
One specific example is System.IO.Path, where the GetFullPath method is not available for Windows Store apps.
It is fairly straightforward to incorporate a replacement for this method in my Windows Store class library and have the original source code invoke this method instead. My question is, is there any way I can do this without modifying the original source code file?
So far, I have not been able to figure out a satisfactory solution to this problem, but I have solved it for my Windows Store class library by implementing e.g. the Path.GetFullPath(string) method in another namespace:
namespace WindowsStoreLib.System.IO {
public static class Path {
public static string GetFullPath(string path) { ... }
}
}
and then adding a preprocessor directive in the original files:
#if NETFX_CORE
using Path = WindowsStoreLib.System.IO.Path;
#endif
Is there an alternative solution to this issue that does not require modification of the original source code files?
No, you cannot, simply.
When I'm doing cross-platform stuff I tend to write a utility class that has different implementations (via #if) for different platforms - then my core code just calls the utility class.
I've been doing something like this lately with Entity Framework classes since I needed to add a specific output of 2 fields as 1 and it wiped it out from the designer.cs on every update. However they were not static classes or static methods, but should work with same.
Create a new class file with the name of the class you want to extend and use the partial qualifier.
namespace WindowsStoreLib.System.IO {
public partial static class Path {
public static string GetFullPath(string path) { ... }
}
}
As Marc said, the preprocessor directive seems to be the only solution.
But when I read "static class" and "existing class", the first thing coming to my mind is "extension method". What would happen if you created an extension method for Path in the same namespace where your code is?
namespace MyNamespace.WhereMyCodeIs
{
using System.IO;
public static class ExtensionMethods
{
public static string GetFullPath(this Path pathObject, string path)
{
// Implementation
}
}
}
I am really not sure if this would work out but maybe there is a work around we could find around this.
I have:
Main Program Class - uses Library A
Library A - has partial classes which mix in methods from Library B
Library B - mix in methods & interfaces
Why would I need a using statement to LibaryB just to get their extension methods working in the main class? That is given that it's Library B that defines the classes that will be extended.
EDIT - Except from code
// *** PROGRAM ***
using TopologyDAL;
using Topology; // *** THIS WAS NEEDED TO GET EXTN METHODS APPEARING ***
class Program
{
static void Main(string[] args)
{
var context = new Model1Container();
Node myNode; // ** trying to get myNode mixin methods to appear seems to need using line to point to Library B ***
}
}
// ** LIBRARY A
namespace TopologyDAL
{
public partial class Node
{
// Auto generated from EF
}
public partial class Node : INode<int> // to add extension methods from Library B
{
public int Key
}
}
// ** LIBRARY B
namespace ToplogyLibrary
{
public static class NodeExtns
{
public static void FromNodeMixin<T>(this INode<T> node) {
// XXXX
}
}
public interface INode<T>
{
// Properties
T Key { get; }
// Methods
}
}
Extension methods are only available if you import the namespace that they are defined in.
Otherwise, the compiler would need to resolve against every single extension method in every single referenced library, which would slow down the compile time.
Also, that would make it impossible to use an extension method if a different namespace contains an extension method with the same signature.
In summary, extension methods are features in their own right and require their namespace to be imported; they are not automatically imported with the namespace of the class that they extend.
This is an unfortunate discoverability issue with extension methods. In order to make them available you need to add a using statement for the namespace containing the static class that has the extensions. Check out this blog about extension methods.
Here is some background on extension methods:
So how is the compiler to know which
extension method to bind? The compiler
looks for extension methods in the
innermost namespace when the call is
made for extension methods and then in
all the namespaces imported by the
"using" clause. This process is
followed moving outward until we reach
the topmost namespace.
Since extension methods can be
imported in to the current context by
the "using" clause and bound to any
object which is assignable(see
convertibility section for details) to
the instance parameter, all sorts of
interesting possibilities open up for
extending the methods implemented by a
type. This can simply be done by
importing a library of extension
methods and using these methods as if
they were declared on a type that you
don't own. This means that
Depending on the library you import the code can be made to do different
things.
The client gets an interesting way to extend a type that he does not own.
My understanding is that using extension methods is just like using any other type, except that you can't qualify them (that is just syntactically impossible), hence the need for using statement. Since you can define multiple of them in different classes in different namespaces, the compiler needs a way to resolve ambiguity.
I envisage that in future Visual Studio will add a feature to import the right namespace when you type in the method name, in a similar way it does so for class and interface names.
Consider this scenario:
namespace FruityNamespace {
public static class FruityExtensions {
public static string ToFunString(this int value) {return value + " bananas"; }
}
}
namespace VegetablNamespace {
public static class VegetablyExtensions {
public static string ToFunString(this int value) {return value + " carrots"; }
}
}
//In some other source file
static void Main(/**/) {
int things = 3;
3.ToFunString(); //error CS1061: 'System.Int' does not contain a definition for 'ToFunString' and no extension method 'ToFunString' accepting a first argument of type 'System.Int' could be found (are you missing a using directive or an assembly reference?)
}
In order to use any of those extension methods you need to import the right namespace:
using FruityNamespace;
//OR
using VegetablyNamespace;
You might ask what happens when you import both namespaces. You get a compiler error just like this:
error CS0121: The call is ambiguous between the following methods or properties: 'VegetablNamespace.VegetablyExtensions.ToFunString(int)' and 'FruityNamespace.FruityExtensions.ToFunString(int)'