Way to add an Extension method?

Question

Say I have a class called LogHelper and it has a static method called GetLogger(string name).

Is there a way to add a static extension method that would just be GetLogger()?

I know that normally extension methods are static where they are declared, but is there a way to appear static on the class they are "Helping"?

You can not add extension methods to static types. Extension methods can only be called from instances. — Steve Guidi, Sep 02 '10 at 17:39

score 6 · Answer 1 · answered Sep 02 '10 at 17:03

6

You could use an extension method:

public static class StringExtensions
{
    public static ILogger GetLogger(this string value)
    {
        ...
    }
}

And then you could use like this:

string foo = "bar";
ILogger logger = foo.GetLogger();

answered Sep 02 '10 at 17:03

Darin Dimitrov

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2

But `GetLogger()` is not static on LogManager. It is an instance method on a string. – Vaccano Sep 02 '10 at 17:21

score 5 · Answer 2 · edited Sep 02 '10 at 17:45

5

You can also use

    public static ILogger GetLogger(string value)
    {
        ...
    }

    public static ILogger GetLogger()
    {
        return GetLogger("Default Value");
    }

This way when you called GetLogger() it would call GetLogger(string value) but with your default value.

edited Sep 02 '10 at 17:45

TrueWill

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answered Sep 02 '10 at 17:23

Gage

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I don't believe this will compile. – Steven Sudit Sep 02 '10 at 17:24
@Steven Sudit, you were correct the way I had it only works on constructors. – Gage Sep 02 '10 at 17:32
1

+1, this is apparently what the OP was looking for. I added a missing "return". – TrueWill Sep 02 '10 at 17:47
1

I think the OP wants this *without* adding that second method to the original class. However, that does not seem to be possible. – Steven Sudit Sep 02 '10 at 18:12
1

@Vaccano Why don't you want to add the second method? – Gage Sep 02 '10 at 18:28

TrueWill · Answer 3 · 2010-09-02T17:49:35.590

I'm not sure how efficient this is, but it should work. log4net has an overload that accepts a Type, and you often want to name the logger after the fully qualified type name.

void Main()
{
    var foo = new Bar.Foo();
    ILog logger = foo.GetLogger();
}   

public static class LogHelper
{
    public static ILog GetLogger(this object o)
    {
        return LogManager.GetLogger(o.GetType());
    }
}

namespace Bar
{
    public class Foo {}
}

// Faking log4net
public class ILog {}
public class LogManager
{
    public static ILog GetLogger(Type type)
    {
        Console.WriteLine("Logger: " + type.ToString());
        return null;
    }
}

The above prints "Logger: Bar.Foo".

P.S. Use "this.GetLogger()" if you want a logger for the current class (assuming non-static method).

score 3 · Answer 4 · answered Sep 02 '10 at 17:40

3

It is not possible to extend static classes with extension methods, unfortunately...

(I'm assuming your LogHelper is static? At least that's what I understood so far.)

answered Sep 02 '10 at 17:40

score 2 · Answer 5 · answered Sep 02 '10 at 18:36

Since what you want is impossible, why not fake it?

After all, it doesn't really matter if your parameterless GetLogger() method is on LogHelper. Just write your own static class, called MyLogHelper or something, and define the method there. The code would look like this:

public static class MyLogHelper
{
    public static ILog GetLogger()
    {
        return LogHelper.GetLogger("MyHardcodedValue");
    }
}

score 1 · Answer 6 · answered Sep 02 '10 at 18:32

1

I see only one solution is to use optional arguments, but unfortunately they appear only in C# 4.0:

public static class LogHelper
{
    public static ILogger GetLogger(string name = "DefaultLoggerName")
    {
        ...
    }
}

answered Sep 02 '10 at 18:32

Sergey Teplyakov

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Way to add an Extension method?

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