Do static members ever get garbage collected?

Question

Do static member variables ever get garbage collected?

For example, let's use the following class.

public class HasStatic {
    private static List<string> shared = new List<string>();

}

And supposed that it's used like this:

//Startup
{
HasStatic a = new HasStatic();
HasStatic b = new HasStatic();
HasStatic c = new HasStatic();
HasStatic d = new HasStatic();
//Something
}
//Other code
//Things deep GC somewhere in here
HasStatic e = new HasStatic();

When a, b, c, and d are garbage collected does the static member shared get collected as well? Could e possibly get a new instance of shared?

Keep in mind that a.shared[1] will have the same value as b.shared[1], and that this element of HasStatic can also be referenced via HasStatic.shared[1]. (Assuming, of course, that there are at least 2 elements in the shared list.) — jp2code

Jon Skeet Jon Skeet · Accepted Answer · 2011-07-06T16:51:53

No, static members are associated with the Type, which is associated with the AppDomain it's loaded in.

Note that there doesn't have to be any instances of HasStatic for the class to be initialized and the shared variable to have a reference to a List<string>.

Unless you're considering situations where AppDomains get unloaded, static variables can be regarded as GC roots forever. (Of course, if something changes the value of HasStatic.shared to reference a different instance, the first instance may become eligible for garbage collection.)

Do static members ever get garbage collected?

2 Answers