public bool Intersects( 
   Envelope envelope
)

// use the convenience builders - don't need to run on the MCT.
Envelope env1 = EnvelopeBuilder.CreateEnvelope(0, 0, 1, 1, SpatialReferences.WGS84);
Envelope env2 = EnvelopeBuilder.CreateEnvelope(0.5, 0.5, 1.5, 1.5, SpatialReferences.WGS84);

bool intersects = env1.Intersects(env2); // true
Envelope env3 = env1.Intersection(env2);


// or use the builder constructor - need to run on the MCT.
using (var builder = new EnvelopeBuilder(0, 0, 1, 1, SpatialReferences.WGS84))
{
  intersects = builder.Intersects(env2);  // true
  env3 = builder.Intersection(env2);
}

// or use the builderEx constructors = don't need to run on the MCT.
EnvelopeBuilderEx builderEx = new EnvelopeBuilderEx(0, 0, 1, 1, SpatialReferences.WGS84);
intersects = builderEx.Intersects(env2);
builderEx.Intersection(env2);   // note this sets the builder to the intersection
env3 = builderEx.ToGeometry() as Envelope;