Passing an Enum as an argument

问题:

I am playing around with trying to make a simple Roguelike game to learn C# a bit better. I am trying to make a general method that I can give it an Enum as an argument, and it will return how many elements are in that Enum as an int. I need to make it as general as possible, because I will have several different classes calling the method.

I have searched around for the last hour or so, but I couldn't find any resources here or otherwise that quite answered my question... I'm still at a beginner-intermediate stage for C#, so I am still learning all the syntax for things, but here is what I have so far:

// Type of element
public enum ELEMENT
{
    FIRE, WATER, AIR, EARTH
}


// Counts how many different members exist in the enum type
public int countElements(Enum e)
{
    return Enum.GetNames(e.GetType()).Length;
}


// Call above function
public void foo()
{
    int num = countElements(ELEMENT);
}

It compiles with the error "Argument 1: Cannot convert from 'System.Type' to 'System.Enum'". I kind of see why it won't work but I just need some direction to set everything up correctly.

Thanks!

PS: Is it possible to change the contents of an enum at runtime? While the program is executing?

回答1:

Try this:

public int countElements(Type type)
{
    if (!type.IsEnum)
        throw new InvalidOperationException();

    return Enum.GetNames(type).Length;
}

public void foo()
{
    int num = countElements(typeof(ELEMENT));
}

回答2:

You could also do this with a generic method. Personally I like the syntax better for the foo() method this way, since you don't have to specify typeof()

    // Counts how many different members exist in the enum type
    public int countElements<T>()
    {
        if(!typeof(T).IsEnum)
            throw new InvalidOperationException("T must be an Enum");
        return Enum.GetNames(typeof(T)).Length;
    }

    // Call above function
    public void foo()
    {
        int num = countElements<ELEMENT>();
    }