C# Member variable overrides used by base class method

问题

OK so I admit right off the top that this is a bit screwy … but it does serve a logical purpose. I’m using C# for a current project and I’m trying to find a way to override a member variable in a derived class, but access the overridden variable in a base class method. To make things more “entertaining” it would be preferable if the overridden member variable was static (this is NOT shown in the example code below).

Here is my sample code:

class baseclass
{
    protected string[] array = null;

    public string method()
    {
        string str = "";
        foreach (string x in this.array)
        {
            str += x + "  "; 
        }

        return str;
    }
}

class subclass1 : baseclass
{
    new string[] array = new string[]
    {
        "class1value1",
        "class1value2",
        "class1value3",
        "class1value4"
    };
}

class subclass2 : baseclass
{
    new string[] array = new string[]
    {
        "class2value1",
        "class2value2",
        "class2value3",
        "class2value4"
    };
}

Any thoughts as to why this doesn't work and a way to get around it?

回答1:

Is there any reason you can't use a virtual property? That would provide exactly the functionality you are looking for. It just wouldn't be a field.

protected abstract string[] array { get; }

...

protected override string[] array { get { return new string[]{"...","..."}; }}

回答2:

Why do you need to override the variable? Looking from your code, just setting the values would be enough, no?

Plus, static variables are tied to the class (not the instance), therefore it's not overridable on any situation.

回答3:

Simply don't use new. Set the array in your subclass' constructor.

EDIT: with code:

class subclass1 : baseclass
{
    public subclass1()
    {
        array = new string[]
        {
            "class1value1",
            "class1value2",
            "class1value3",
            "class1value4"
        };
    }
}

class subclass2 : baseclass
{
    public subclass2()
    {
        array = new string[]
        {
            "class2value1",
            "class2value2",
            "class2value3",
            "class2value4"
        };
    }
}

回答4:

class BaseClass
{
    public virtual string Method()
    {
        return string.Empty;
    }
}

abstract class BaseClass<T> : BaseClass where T : BaseClass<T>
{
    protected static string[] strings;

    public override string Method()
    {
        return string.Join("  ", strings);
    }
}

class Subclass1 : BaseClass<Subclass1>
{
    static Subclass1()
    {
        strings = new[] { "class1value1", "class1value2", "class1value3" };
    }
}

class Subclass2 : BaseClass<Subclass2>
{
    static Subclass2()
    {
        strings = new[] { "class2value1", "class2value2", "class2value3" };
    }
}

The important part is the generic parameter T which basically functions as an index to the string arrays.

回答5:

You're trying to get polymorphic behavior from the array but you're defining it for class local behavior.

The array has to be virtual or method() in the base class will compile to always access the array in the base class - the array should also be a property not a field to do this, i.e.,

string[] _array = { ... }; /base class local values protected virtual string[] array { get { return _array; } } //makes the array property overridable

then in the subclasses, you'll need to do

string[] _array = { ... }; //subclass local values virtual string[] array { get { return _array; } } //this overrides the base class property

in order to get the desired affect

来源：https://stackoverflow.com/questions/1112458/c-sharp-member-variable-overrides-used-by-base-class-method

标签

overriding