This sample is taken from my F# book, Foundations of F#, available from pre-order now ;)

If you have a function that returns a list.

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let getList() =
    [1; 2; 3]

You can iterater though it with the following code:

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static void GetList()
{
    Microsoft.FSharp.Collections.List<int> l = DemoModule.getList();
    while (l != null)
    {
        Console.WriteLine(l.Head);
        l = l.Tail;
    }
}

However, I use this as an example to say that it is difficult to iterate over F# lists in C# so return System.Collections.Generic.Lists instead. Just call List.to_ResizeArray before you return your list (ResizeArray is the F# name for a generic list). This way you also avoid the depency on FSLib.dll which will save you trouble, as new versions of this are released quite frequently.