Question

A co-worker has an object that has a bunch of generic list collections on it. Each type in the list implements a given interface. He wants to be able to create a list that contains all the other lists so he can loop through and call the method the objects implement. Below is a simple example.

 List<Dx> dxs = new List<Dx>();
 dxs.Add(new Dx());
 dxs.Add(new Dx());

 List<Proc> procs = new List<Proc>();
 procs.Add(new Proc());

 List<List<IClean>> lists = new List<List<IClean>>();
 lists.Add(procs); // Error here
 lists.Add(dxs); // Error here

 foreach (List<IClean> list in lists)
 {
     foreach (IClean i in list)
     {        
         i.Clean();
     }
 }

Dx and Proc both implement IClean. This is the goal. Is something like this possible? Or, is this bad programming?

.NET Version 4.0

Answer 1

You could just have a single List<IClean> that hold both implementations of IClean.

var list = new List<IClean>();
    list.Add(new Dx());
    list.Add(new Proc());

foreach(var clean in list)
{
   clean.Clean();
}

Furthermore, if you actually need to maintain two separate implementation lists and then process them together, you could do something like this:

var dx = new List<Dx>();
var proc = new List<Proc>();

List<IClean> list = new List<IClean>();
list.AddRange(dx);
list.AddRange(proc);

foreach(var clean in list)
{
   clean.Clean();
}