C# constructors with both a this() and a base()

Let’s say I have the following, rather simple, class hierarchy:

class FooBase
{
    public FooBase(int a)
    {
        Console.WriteLine("FooBase({0})", a);
    }
}

class MyFoo
{
    public MyFoo(int a, string s)
    {
        Console.WriteLine("MyFoo({0}, \"{1}\"", a, s);
    }
}

Now, let’s say I’m adding a new constructor to MyFoo. You can use the following syntax to call another constructor with different parameters on your own type:

MyFoo()
    : this(10, "something else")
{
    Console.WriteLine("MyFoo()");
}

In this case, the output after constructing with this constructor would be:

MyFoo(10, "something else")
MyFoo()

You can also use the following syntax to call a base class’s constructor:

MyFoo()
  : base(10)
{
    Console.WriteLine("MyFoo()");
}

And in this case, the output after constructing with this constructor would be:

FooBase(10)
MyFoo()

So why can’t you call both, like so (for example):

MyFoo()
    : base(10), this(15, "something else")
{
    Console.WriteLine("MyFoo()");
}

? In this case, I would expect the base class’s constructor to run first, MyFoo(int, string) next, and then the body of the current constructor to run third, giving the following output:

FooBase(10)
MyFoo(15, "something else")
MyFoo()

I can’t think of any reason for why that wouldn’t be allowed. Perhaps you can do it, and I just don’t know the syntax, but when you look at articles in this topic (for example, this one on MSDN) it just lists the first two that I mentioned, without any mention of whether you can (or how to, or why you can’t) combine them.