In C/C++, I have a bunch of functions that I call from main(), and I want to rewrite this in C#. Can I have stand alone functions(methods) or do I have to put them in another class? I know I can have methods within the same class, but I want to have a file for each function/method.
Like this works:
using System.IO;
using System;
class Program
{
static void Main()
{
House balls = new House();
balls.said();
}
}
public class House
{
public void said()
{
Console.Write("fatty");
Console.ReadLine();
}
}
But then I have to create an instance of House and call said(), when in C I can just call said().
For reference, I want to add the using static addition of C# 6 here.
You can now use methods of a static class without having to type the name of that class over-and-over again. An example matching the question would be:
House.cs
public static class House
{
public static void Said()
{
Console.Write("fatty");
Console.ReadLine();
}
}
Program.cs
using static House;
class Program
{
static void Main()
{
Said();
}
}
No. Make them static and put them in a static utility class if they indeed don't fit within any of your existing classes.
If using C# 9 it is now kinda possible, thanks to the top-level statements feature.
In your executable project, the following syntax is now allowed:
using SomeNamespace;
// The following statements are seemingly defined without even a method,
// but will be placed inside a "Main" static method in a "$Program" static class
SayHello();
var classFromSomeNamespace = new SomeClass(); // from SomeNamespace
classFromSomeNamespace.SomeMethod();
// This function is seemingly defined without a class,
// but on compile time it will end up inside a "$Program" static class
void SayHello()
{
Console.WriteLine("Hello!");
}
// Here the "traditional" syntax may start
namespace SomeNamespace
{
public class SomeClass
{
public void SomeMethod()
{
Console.WriteLine("SomeMethod called");
}
}
}
It should be noted, that the above syntax is valid only for a single file in a project, and the compiler actually still wraps this all inside a $Program static class with static methods. This feature was introduced specifically to avoid boilerplate code for the program entry point, and make it possible to easily write "scripts" in C#, while retaining the full .NET capabilities.
There is no concept of standalone functions in C#. Everything is an object.
You can create static methods on some utility class, and call those without creating an instance of a class eg
class Program
{
static void Main()
{
House.said();
}
}
public class House
{
public static void said()
{
Console.Write("fatty");
Console.ReadLine();
}
}
You have to put them in a class, but the class can be static as others mentioned. If you REALLY want to have a separate file for each method, you can mark the class as partial to get the following:
Program.cs
----------
class Program
{
static void Main()
{
House.said();
House.saidAgain();
}
}
House-said.cs
-------------
public static partial class House
{
public static void said()
{
Console.Write("fatty");
Console.ReadLine();
}
}
House-saidAgain.cs
------------------
public static partial class House
{
public static void saidAgain()
{
Console.Write("fattyAgain");
Console.ReadLine();
}
}
I wouldn't recommend separating each one out, however. Partial classes are mostly used so that designer-generated code won't overwrite any custom code in the same class. Otherwise you can easily end up with hundreds of files and no easy way to move from one method to another. If you think you need a partial class because the number of methods is getting unmaintainable, then you probably need to separate the logic into another class instead.
Although the concept of stand-alone functions exists in .NET, C# doesn't allow you to specify such functions. You need to stick them inside a static Utils class or similar.
If you declare your method as static (that is: public static void said()) then you can just call it with House.said(), which is as close as you'll get in C#.
You could add all your methods to the Program class, but this would quickly become an unmaintainable mess, commonly referred to as the God Class or Ball of Mud anti-pattern.
Maintaining a single file for each function would similarly become a huge mess. The questions "Where do I put my methods" and "What classes should I create" are answered by Design Patterns. Classes aggregate behavior (functions) and should do one thing (Single Reponsibility.)
Related
I am making a DLL of helper functions and I want to call them without calling the class they live in. For example:
namespace HelperFunctions
{
public static class Greetings
{
public static void greet()
{
Console.WriteLine("hello!");
}
}
How to I modify the above code so that I can do this:
using HelperFunctions;
namespace MyConsoleApp
{
class Program
{
static void Main()
{
greet();
}
}
}
Assumptions/Understandings:
I understand I can call Greetings.greet() but I dont want to.
I understand I will have to come up with unique names for my functions that won't clash with anything from the System namespace (or whatever other references I am using)
Presently, you can't.
When the next version of C# is released, you'll be able to write:
using HelperFunctions.Greetings;
and it will work.
This question already has answers here:
Organizing c# code into different files
(4 answers)
Closed 8 years ago.
I recently inherited some code that is several thousand lines long and extremely disorganized.
I'm trying to re-factor it so that code is at least easier to find, but since it was built in visual studio, everything is contained within a single "form" class, and the way it's written makes it difficult to separate code without breaking something.
Is there a way that I could have the code live in a different file, but still keep it in the same class?
Yes. Just use the partial keyword for each "part" of the class in the class' files.
// example class A in file: A1.cs
public partial class A { }
// example class A in file: A2.cs
public partial class A { }
More information can be found at MSDN and a thousand other sites and blogs.
Also consider using #region directive to split the code into more navigable chunks. This will also be easier to navigate to since the one file can keep the name with the class, and no one has to dig for the various pieces of this same class in different files.
Yes, it is possible. This is the way Visual Stuido generates code for things like Win Forms. It enable to split the implementation into two separate files, and enables the user to alter just one and thus reducing the probability to screw something up.
The concept is called partial classes. You define the same class in two different files, and but class definitions need to have the word partial in font. It is also possible for structs and interfaces.
Read more here:
http://msdn.microsoft.com/en-us/library/wa80x488.aspx
Use partial classes. For example:
If you have a class in Example.cs as such:
public class Example
{
public void Func1()
{
}
public void Func2()
{
}
public void Func3()
{
}
public void Func4()
{
}
}
You can easily change it to:
Example.cs
public partial class Example
{
public void Func2()
{
}
public void Func4()
{
}
}
RestOfTheExample.cs
public partial class Example
{
public void Func1()
{
}
public void Func3()
{
}
}
Hope this helps!!!
By using the partial classes as for ex
public partial class Employee
{
public void DoWork()
{
}
}
public partial class Employee
{
public void GoToLunch()
{
}
}
This requirement is driven by grief that peer developers mix extension method on different types into one xxxExt class.
It still works because compiler takes care of the resolution by looking at he imported namespaces. But it is annoying and not easy to maintain when it comes to overlapping types.
Is it at all possible to constraint the type extensions that could be written in a specific xxExt class? Circulating manual rules does not work well... possibly something like a static code analysis if not compiler level restriction?
Code (which I want to restrict in this class is IsActiveRisk method).
public static class TradeDataExt{
public static bool IsActiveTrade(this TradeData tradeData){...}
public static bool IsActiveRisk(this RiskData riskData) {...}
}
This is more of a "desired" feature, not sure if at all possible.
Comments/suggestions would be helpful.
First of all, it seems to me that you wrote your example and forgot the more important keyword of the extension methods, you missed the keyword "this" right before your parameter! :)
i'm guessing you meant:
public static class TradeDataExt
{
public static bool IsActiveTrade(this TradeData tradeData){...}
public static bool IsActiveRisk(this RiskData riskData) {...}
}
Ok, first point said, now let's take a look at your question:
This requirement is driven by grief that peer developers mix extension
method on different types into one xxxExt class.It still works because
compiler takes care of the resolution by looking at the imported
namespaces.
In fact, what you are saying is the exact opposite of the truth of how extensions methods work!
When you declare a static class with static methods, the methods will be automatically available when declaring using "namespace", and not of the name of the class! (unless you are in scenario that you have a project with several .cs files that are partial classes of the same static class..... what i think does not make sense)
Take a look at this example:
namespace Gabriel.Extensions
{
public static class ClassWithSameName
{
public static bool IsActiveTrade(this TradeData tradeData){...}
}
}
namespace John.Extensions
{
public static class ClassWithSameName
{
public static bool IsAGoodDeal(this TradeData tradeData){...}
}
}
If you look at the example, both classes have the same name, but since they are in different namespaces, they will only extend the TradeData class when explicitly declaring the "using" of each namespace. So, i would say this is the way to go for you:
You should use the namespaces to control the types extensions being created, so you can have the namespace like XXXX.Extensions.Validation, XXXXX.Extensions.Calculation, XXXXX.Extensions.ServicesProvider and so on... instead of using all at the same namespace (because things can get complicated...add hundreds of extensions methods in the same namespace, is not a best practice at all.
Your code should look like this:
namespace TradeDataExtensions.Validation
{
public static class ClassWithSameName
{
public static bool IsActiveTrade(this TradeData tradeData){...}
}
}
namespace TradeDataExtensions.Analytics
{
public static class ClassWithSameName
{
public static decimal ExpectedReturn(this TradeData tradeData){...}
}
}
I have a class
public class Foo{
public Foo{...}
private void someFunction(){...}
...
private Acessor{
new Acessor
}
}
with some private functionality (someFunction). However, sometimes, I want to allow another class to call Foo.SomeFunction, so I have an inner class access Foo and pass out that:
public class Foo{
public Foo{...}
private void someFunction(){...}
...
public Acessor{
Foo _myFoo;
new Acessor(Foo foo){_myFoo = foo;}
public void someFunction(){
_myFoo.someFunction();
}
}
}
With this code, if I want a Foo to give someone else pemission to call someFunction, Foo can pass out a new Foo.Accessor(this).
Unfortunately, this code allows anyone to create a Foo.Accessor initiated with a Foo, and they can access someFunction! We don't want that. However, if we make Foo.Accessor private, then we can't pass it out of Foo.
My solution right now is to make Acessor a private class and let it implement a public interface IFooAccessor; then, I pass out the Foo.Accessor as an IFooAccessor. This works, but it means that I have to declaration every method that Foo.Accessor uses an extra time in IFooAccessor. Therefore, if I want to refactor the signature of this method (for example, by having someFunction take a parameter), I would need to introduce changes in three places. I've had to do this several times, and it is starting to really bother me. Is there a better way?
If someFunction has to be accessible for classes in the same assembly, use internal instead of private modifier.
http://msdn.microsoft.com/en-us/library/7c5ka91b(v=vs.71).aspx
If it has to be accessible for classes which are not in the same assemble then, it should be public. But, if it will be used by just a few classes in other assemblies, you probably should think better how you are organizing you code.
It's difficult to answer this question, since it's not clear (to me at least) what exactly you want to achieve. (You write make it difficult for someone to inadverdantly use this code in a comment).
Maybe, if the method is to be used in a special context only, then explicitly implementing an interface might be what you want:
public interface ISomeContract {
void someFunction();
}
public class Foo : ISomeContract {
public Foo() {...}
void ISomeContract.someFunction() {...}
}
This would mean, that a client of that class would have to cast it to ISomeContract to call someFunction():
var foo = new Foo();
var x = foo as ISomeContract;
x.someFunction();
I had a similar problem. A class that was simple, elegant and easy to understand, except for one ugly method that had to be called in one layer, that was not supposed to be called further down the food chain. Especially not by the consumers of this class.
What I ended up doing was to create an extension on my base class in a separate namespace that the normal callers of my classes would not be using. As my method needed private access this was combined with explicit interface implementation shown by M4N.
namespace MyProject.Whatever
{
internal interface IHidden
{
void Manipulate();
}
internal class MyClass : IHidden
{
private string privateMember = "World!";
public void SayHello()
{
Console.WriteLine("Hello " + privateMember);
}
void IHidden.Manipulate()
{
privateMember = "Universe!";
}
}
}
namespace MyProject.Whatever.Manipulatable
{
static class MyClassExtension
{
public static void Manipulate(this MyClass instance)
{
((IHidden)instance).Manipulate();
}
}
}
I currently have a function that looks like this:
public void AnimateLayoutTransform(object ControlToAnimate)
{
//Does some stuff
}
I use this function in a lot of different projects, so I want it to be very reusable. So for now I have it in a .cs file, enclosed in a namespace and a class:
namespace LayoutTransformAnimation
{
public class LayoutAnims
{
public void AnimateLayoutTransform(object ControlToAnimate)
{
//Do stuff
}
}
}
The problem with this is that to use this one function in a given project, I have to do something like
new LayoutTransformAnimation.LayoutAnims().AnimateLayoutTransform(mygrid);
Which just seems like a lot of work to reuse a single function. Is there any way to, at the very least, use the function without creating a new instance of the class? Similar to how we can Double.Parse() without creating a new double?
One option is to make it a normal static method. An alternative - if you're using C# 3.0 or higher - is to make it an extension method:
public static class AnimationExtensions
{
public static void AnimateLayoutTransform(this object controlToAnimate)
{
// Code
}
}
Then you can just write:
mygrid.AnimateLayoutTransform();
Can you specify the type of the control to animate any more precisely than "Object"? That would be nicer... for example, can you only really animate instances of UIElement? Maybe not... but if you can be more specific, it would be a good idea.
You could make it into a static method.
MSDN Example
I find it useful to have a static util class with static methods in them which can be used within the project namespace.
public static class YourUtilsClass
{
public static Void YourMethod()
{
//do your stuff
}
}
You can call it like so: YourUtilsClass.YourMethod()
namespace LayoutTransformAnimation
{
public class LayoutAnims
{
public static void AnimateLayoutTransform(object ControlToAnimate)
{
//Do stuff
}
}
}
LayoutTransformAnimation.LayoutAnims.AnimateLayoutTransform(something);