public class Program {

    public static void Main() {

        ExampleEnum? e = null;

        e = ExampleEnum.VariantA;

        var o = new ExampleClass(e.Value);

    }

}

​

public class ExampleClass {

    public ExampleEnum E;

    public ExampleClass(ExampleEnum e) {

        this.E = e;

    }

}

​

public enum ExampleEnum {

    VariantA,

    VariantB

}