Question

I am making a component based system (each object delegates all functionality to a variety of components which can be added at runtime) and want to be able to define my objects in XML files for ease. I know how to use Activator.CreateInstance to create my objects from strings, but I require full classnames and assembly names.

The issue comes from the fact that these components may be either pre-built in my library (say assembly FirstAssembly.dll and namespace Foo.Bar) or defined specifically for my game (say assembly SecondAssembly.dll and namespace Second.Blah).

//In some assembly FirstAssembly.dll

namespace Foo.Bar
{
class SomeClassA
{
}

class SomeClassB
{
}
}

//In some assembly SecondAssembly.dll

namespace Second.Blah
{
class SomeClassC
{
}

class SomeClassD
{
}
}

//In my XML..I would much prefer
<class="SomeClassA"...> </class>
<class="SomeClassD"...> </class>

//Over this, which would just need to check FirstAssembly and SecondAssembly and error handle
<class="Foo.Bar.SomeClassB"...></class>
<class="Second.Blah.SomeClassD"...></class>

//Which I would much prefer over
<class="Foo.Bar.SomeClassB" assembly="FirstAssembly"...></class>
<class="Second.Blah.SomeClassD" assembly="SecondAssembly"...></class>

The last solution would be easy, if rather annoying – I need assembly names, or at least some way of saying ‘component from library’ or ‘component from game’.

The second solution is probably easier – I just need (some way) of checking – probably just try/catch – if the class is in FirstAssembly; if not, try SecondAssembly.

The first solution is what I really want to do, but I do not think it possible. The amount of namespaces would make it difficult.

tl;dr Is there a way I can make this system work so my XML files look as close to the first solution as possible? If not, is the second solution viable?

Answer 1

It sounds like you want something like:

Type targetType = (from assembly in candidateAssemblies
                   from type in assembly.GetTypes()
                   where type.Name == nameFromXml
                   select type).FirstOrDefault();

Note that:

• If there are multiple matches, this will just return the first one.
• If there are no matches, this will return null
• You may wish to add extra conditions, such as public types etc