IList的C＃参数 <IList<(ClassType)> &gt;

Question

I can't seem to figure out why the following doesn't work.

From reading around it seems it must be somehow related to something like this .

public class Test<T>
{
    public void SomeFunction(IList<IList<T>> ListOfLists)
    {
    }
}

....

List<List<SimpleClass>> lists = new List<List<SimpleClass>>();
new Test<SimpleClass>().SomeFunction( (IList<IList<SimpleClass>>)lists );

How can I require a list to actually be a list of lists? I can't seem to grasp what I am doing wrong.

Thanks,

Answer 1

A List<List<SimpleClass>> isn't an IList<IList<SimpleClass>> .

For example, for the latter type, you could call lists.Add(new SimpleClass[5]) as SimpleClass[] implements IList<SimpleClass> . But you can't do that with a List<List<SimpleClass>> , because each element has to be a List<SimpleClass> .

This would be okay though:

List<IList<SimpleClass>> lists = new List<IList<SimpleClass>>();