Envelope env1 = EnvelopeBuilder.CreateEnvelope(0, 0, 1, 1, SpatialReferences.WGS84);
Envelope env2 = EnvelopeBuilder.CreateEnvelope(0.5, 0.5, 1.5, 1.5, SpatialReferences.WGS84);
Envelope env3 = env1.Union(env2);
double area = env3.Area;
double depth = env3.Depth;
double height = env3.Height;
double width = env3.Width;
double len = env3.Length;
MapPoint centerPt = env3.Center;
Coordinate2D coord = env3.CenterCoordinate;
bool isEmpty = env3.IsEmpty;
int pointCount = env3.PointCount;
// coordinates
//env3.XMin, env3.XMax, env3.YMin, env3.YMax
//env3.ZMin, env3.ZMax, env3.MMin, env3.MMax
bool isEqual = env1.IsEqual(env2); // false