MLeader mld = new MLeader();
mld.SetDatabaseDefaults();
mld.ContentType = ContentType.BlockContent;
mld.BlockContentId = blkid;
mld.AddLeaderLine(cp);
mld.SetVertex(0, 1, cp+(new Vector3d (15,15,0)));
mld.ArrowSymbolId = blockTable["_NONE"];
mld.ArrowSize = 0;
mld.DoglegLength = 2;
mld.LeaderLineType = LeaderType.StraightLeader;