Question

I need to copy a sub set of items from one list to another. However I do not know what kind of items are in the list – or even if the object being passed is a list.

I can see if the object is a list by the following code

t = DataSource.GetType();

if (t.IsGenericType)
{
    Type elementType = t.GetGenericArguments()[0];
}

What I cannot see is how to get to the individual objects within the list so I can copy the required objects to a new list.

Answer 1

The code you wrote will not tell you if the type is a list.
What you can do is:

IList list = DataSource as IList;
if (list != null)
{
  //your code here....
}

this will tell you if the data source implements the IList interface.
Another way will be:

    t = DataSource.GetType();

    if (t.IsGenericType)
    {
        Type elementType = t.GetGenericArguments()[0];
        if (t.ToString() == string.Format("System.Collections.Generic.List`1[{0}]", elementType))
        {
              //your code here
        }
    }