// Use a builderEx convenience method or use a builderEx constructor.
// convenience methods don't need to run on the MCT.
Envelope envelope = EnvelopeBuilderEx.CreateEnvelope(100.0, 100.0, 500.0, 500.0);
// shrink the envelope by 50%
Envelope result = envelope.Expand(0.5, 0.5, true);
// builderEx constructors don't need to run on the MCT.
EnvelopeBuilderEx builderEx = new EnvelopeBuilderEx(100.0, 100.0, 500.0, 500.0);
builderEx.Expand(0.5, 0.5, true);
envelope = builderEx.ToGeometry() as Envelope;