如何从静态类返回类实例？

Question

I want use a static class that must contains global variables, so I can access to all application controls simply from a variable. Actually I've this implementation:

public static class Globals
{
    public static HeadToHead Head2Head
    {
       get { return Resources.Controls.HeadToHead; }
    }
}

in the case above, I want return the instance of HeadToHead control, the control look like this:

public partial class HeadToHead : UserControl
{
    public static int HomeId = 0;

}

my goal is to access to the static variables of this control, like: Globals.Head2Head.HomeId

but I get this error on this line: get { return Resources.Controls.HeadToHead; } get { return Resources.Controls.HeadToHead; }

HeadToHead is a type which is not valid in the given context

Answer 1

You're returning what looks like a type from a property that seems to be declaring an instance of that type. If you truly want to return that type, there's syntax for that (I don't remember any more, I think in c# it's classname.type). If you want to return an instance, then you need to get that instance from somewhere.

As an aside, static instances of UI controls are a bad idea, and a code smell.

Answer 2

You have to instantiate an instance of the type and return that. As you want a single global instance you could use the static constructor.

public static class Globals {

    static Globals(){
       Head2Head = new Resources.Controls.HeadToHead();
    }

    public static HeadToHead Head2Head { get; private set; }
}

There are few situations in which you would actually want to do this but common static settings that do not change in the life of the application might be one of them. As HeadToHead inherits from UserControl that does not really seem to be the case, an instance of a UserControl should ideally never be static.