Question

I have a base class “Element” and derived two other classes from it, “Solid” and “Fluid”.

    class Element
    {...}

    class Solid : Element
    {
        public const int ElemType = 2;
        ...
    }

    class Fluid : Element
    {
        public const int ElemType = 3;
        ...
    }

I have made an instance of “Element” class, “E1”. The following method is supposed to get an integer “ElType” and “E1” as its arguments and assign to “E1” as “Solid” or “Fluid” Element (or any other “Element” which will be introduced later). I mean, “E1” should be assigned to a “Solid” type if “IElType == 2” and “Fluid” type if “IElType == 3” and …. I wanted to make it possible for my colleagues to derive as many classes as they want, from “Element” class, and be sure that only by setting a proper value for “ElemType” the program will recognize their “Element”s.

    private static void ElemInitializer(int ElType, out Element E1)
    {
        E1 = new Element();
        Type T1 = typeof(Element);
        Type[] T2 = Assembly.GetAssembly(T1).GetTypes();
        List<Type> T3=new List<Type>();
        foreach (Type t1 in T2)
        {
            if (t1.IsSubclassOf(T1))
            {
                MemberInfo[] M1 = t1.GetMembers();
                foreach (MemberInfo m1 in M1)
                {
                    if (m1.Name == "ElemType")
                    {
                        FieldInfo F1 = t1.GetField("ElemType");
                        int int1 = (int)F1.GetValue(t1);
                        if (int1 == ElType)
                        {
                            // Here I want to assign to E1 as t1 type. Such as:
                            // E1 = new t1(); Of course this is wrong!
                        }
                    }
                }
            }
        }
    }

Here is the problem , I want “E1” be of type “t1”, but it is not possible to do this by a simple code like this:

E1 = new t1(); //Of course this is wrong!

Is there any way to assign to “E1” as “t1” type? Sorry for nontechnical English.

Answer 1

First of all, use a better naming convention, it makes it easier to help you and it will help your self in the long run too. The below code should do it

private static void ElemInitializer(int ElType, out Element E1)
{
    E1 = new Element();
    Type typeofElement = typeof(Element);
    Type[] assemblyTypes = Assembly.GetAssembly(T1).GetTypes();
    foreach (Type elementType in assemblyTypes )
    {
      if (elementType.IsSubclassOf(typeofElement))
      {
        FieldInfo field = elementType.GetField("ElemType");
        int elementId = (int)field.GetValue(elementType);
        if (elementId == ElType)
        {
           E1 = (Element)Activator.CreateInstance(elementType);
           return;
        }
      }
    }
}