C# ISurface.CreateTrimmedSheet4() Curves Parameter

What goes in this parameter?

Let's say I made a temporary sphere following Create Temp Spherical Sheet Body

I had to use

ball.CreateTrimmedSheet4(new Curve[] { null }, true);
// or
ball.CreateTrimmedSheet4(new object[] { null }, true);

// vv these don't work, I get runtime exceptions vv
ball.CreateTrimmedSheet4(new object[] { }, true);
ball.CreateTrimmedSheet4(new Curve[] { }, true);
ball.CreateTrimmedSheet4(null, true); // especially this one

The docs say to insert a null between trimming loops, but if your surface is periodic, you can forego the Curves parameter. The example used an Empty. What does that mean in terms of C#? I'm not well acquainted with VBA, so I don't know what the C# equivalent of Empty is, and neither null nor an empty array seems to be the substitute.

Are there examples of using CreateTrimmedSheet4() for other shapes?