CODEWITHSUNDEEP
c#.net
MB.
MB.

Reputation: 7533

What hack can I use to define a C# property with same name as class?

I'm using C# to make a .Net class library (a DLL) that will be distributed widely. I have an abstract class called Value, and I want it to have an abstract double property that is also called Value i.e.

public abstract class Value {

    // Only accessible by subclasses within the project.
    internal Value() {}

    public abstract double Value {
        get;
    }

}

But the C# compiler won't allow this - I get the message "member names cannot be the same as their enclosing type", as discussed here.

I understand that the easiest thing to do would be to change the name of the property or the name of the class... But really I want the names to be like that, and I'm quite happy to implement an ugly hack to get it that way. So long as it works properly from external code that uses this DLL.

Unlike C#, VB.Net will allow me to define a property with the same name as the class, so I'm currently investigating merging my C# project with a VB project that defines the Value class (and its Value property) to make one DLL. This doesn't seem to be quite as straightforward as I was hoping.

Another option would be to re-write the whole project in VB... Not very appealing, but I'll consider it if necessary. I prefer C# over VB.Net but my priority is to get the built DLL the way I want it.

I'm wondering what other alternatives there might be. Any ideas for a good way to hack this?

EDIT: From the comments below it's clear that quite a number of people don't think much of the name "Value" for a class... Could anyone explain why it's so bad? I know it's not very descriptive, but I think it fits well in the context of my project. Is it because it's a keyword in C# that's used in property setters?

Upvotes: 10

Views: 5066

Answers (6)

Marco Concas
Marco Concas

Reputation: 1892

You can make an abstract class then you can inherit from it. This is a practical example:

abstract class FoodAbstract
{
    public string Food { get; set; }
}

class Food : FoodAbstract
{

}

Then, you can use it from Food class (the base class with the same name of the property):

var food = new Food().Food

Upvotes: 0

MB.
MB.

Reputation: 7533

Bowing to popular opinion, I've decided to rename my Value class to DataValue. I'm pretty happy with that name, and it means I don't need any hacks to have the property called Value. So thank you very much to everyone for the feedback.

But, despite the useful answers, I still don't think the question has been answered ideally. None of the proposed solutions do exactly what was asked for, or at least not without side effects like the requirement for an otherwise-superfluous interface or public class. I should probably have been clearer in my question that I was perfectly happy to consider a hack that involved unsafe code, or modification of intermediate language or some such, as my priority was to get the public API of the DLL the way I wanted it, irrespective of whatever messy hacks might lurk hidden within it's source.

So here's the best solution that I could come up with. I haven't actually done it myself (no need now I'm using a different name for the class), but I don't have any reason to suspect that it won't work:

  1. In the solution that contains your C# class-library project, add a new VB class-library project.

  2. In the VB project, create the class (Value in my original example). In VB you'll have no problems adding a property with the same name as the class.

  3. If your VB class has internal methods that need to be referenced by your C# code, reference the C# assembly using InternalsVisibleTo in your VB class.

  4. You should now be able to reference your VB class from your C# project. But when you build the solution you'll get two separate DLLs: one for the C# code and one for the VB code. It looks like the ILMerge tool makes it very straightforward to merge the two DLLs into one (just one call from the command line).

So finally you should have a single DLL that contains the class with the property of the same name, and all the code in your C# project. Other projects that use that DLL (C#, VB, or any other .Net language) should not see your hacky effort - all they'll see is a coherent API with no superfluous public classes or interfaces.

Upvotes: 2

Jason Williams
Jason Williams

Reputation: 57902

Value is a terrible name for a class. It's extremely vague, so it does nothing to describe what a Value represents, and it clashes with the reserved word 'value'. You will find yourself using value = Value.Value, wondering why your code makes no sense, and eventually trying to fix a hideous bug that is a direct result of using 'value' instead of Value or value or _value or this.value. And what happens when you have to store another kind of arbitrary number? Will you call it Value2?

Name the class with a more specific and meaningful name and the problem will no longer exist. Don't fix the symptoms - fix the cause.

Even if you only rename it to "DataValue" or 'MySystemValue', you will be doing yourself a great service.

Upvotes: 2

Michael Petito
Michael Petito

Reputation: 13161

If your class is representative of a double (except for some additional metadata), you could opt for a conversion operator:

public abstract class Value
{
    protected abstract double GetValue();

    public static explicit operator double (Value value)
    {
        return value.GetValue();
    }
}

Then your client code could access the metadata or cast an instance of type Value to a double. Depending on the metadata and usage, you might make the conversion implicit so you don't have to do an explicit cast, and you might define a conversion from double to Value.

There is a similar approach used by the System.Xml.Linq assembly where, for example, XElement can be cast to any primitive type as a means of accessing its "value".

Upvotes: 3

Grokys
Grokys

Reputation: 16526

As other people have said, this is not possible in C#.

Other people have criticised the name Value as a class, and while I agree it's likely too generic, I can see situations where it may make sense.

Bearing that in mind, if Value is an abstract class, perhaps ValueBase might be a decent, conformant, name? Much of the .Net framework (particularly WPF) uses XxxBase.

Another option to consider is prefixing the class name with the name of your project, as in FooValue.

Upvotes: 2

Marc Gravell
Marc Gravell

Reputation: 1063013

You cannot do that directly. You could, however, consider:

  • impelenting an interface with a Value member, and using explicit interface implementation (callers would have the use the interface, though)
  • renaming it in the class, and using an extension method to expose a Value() method, so obj.Value() works
  • rename it in the class, but expose it as Value in the subclasses

Ugly hack:

public abstract class ValueBase {
    public abstract double Value { get; }
    internal ValueBase() {}
}
public abstract class Value : ValueBase {
    internal Value() {}
}
public sealed class ValueReal : Value {
    public override double Value { get { return 123; } }
}

Upvotes: 9

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