public override DatumTransformation GetInverse()

// create from wkid
GeographicTransformation gt1478 = 
  ArcGIS.Core.Geometry.GeographicTransformation.Create(1478);
string name = gt1478.Name;
string wkt = gt1478.Wkt;
int wkid = gt1478.Wkid;

// create from wkt
GeographicTransformation another_gt1478 = 
     ArcGIS.Core.Geometry.GeographicTransformation.Create(wkt);

// inverse
GeographicTransformation inverse_gt148 = 
               another_gt1478.GetInverse() as GeographicTransformation;
bool isForward = inverse_gt148.IsForward;