public string GetWkt2( 
   WktFormatMode wktFormatMode
)

{
  SpatialReference sr = SpatialReferences.WebMercator;

  // Get Esri WKT
  string wkt = sr.Wkt;
  /*
    PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere",
     GEOGCS["GCS_WGS_1984",
      DATUM["D_WGS_1984",
       SPHEROID["WGS_1984", 6378137.0, 298.257223563]],
      PRIMEM["Greenwich", 0.0],
      UNIT["Degree", 0.0174532925199433]],
     PROJECTION["Mercator_Auxiliary_Sphere"],
     PARAMETER["False_Easting", 0.0],
     PARAMETER["False_Northing", 0.0],
     PARAMETER["Central_Meridian", 0.0],
     PARAMETER["Standard_Parallel_1", 0.0],
     PARAMETER["Auxiliary_Sphere_Type", 0.0],
     UNIT["Meter", 1.0]]
  */

  // Get OGC WKT2
  string wkt2 = sr.GetWkt2(WktFormatMode.None);
  /*
    PROJCRS["WGS_1984_Web_Mercator_Auxiliary_Sphere",
     BASEGEOGCRS["GCS_WGS_1984",
      DYNAMIC[FRAMEEPOCH[1990.5], MODEL["AM0-2"]],
      DATUM["D_WGS_1984",
       ELLIPSOID["WGS_1984", 6378137.0, 298.257223563, LENGTHUNIT["Meter", 1.0]]],
      PRIMEM["Greenwich", 0.0, ANGLEUNIT["Degree", 0.0174532925199433]],
      CS[ellipsoidal, 2],
      AXIS["Latitude (lat)", north, ORDER[1]],
      AXIS["Longitude (lon)", east, ORDER[2]],
      ANGLEUNIT["Degree", 0.0174532925199433]],
     CONVERSION["Mercator_Auxiliary_Sphere",
      METHOD["Mercator_Auxiliary_Sphere"],
      PARAMETER["False_Easting", 0.0, LENGTHUNIT["Meter", 1.0]],
      PARAMETER["False_Northing", 0.0, LENGTHUNIT["Meter", 1.0]],
      PARAMETER["Central_Meridian", 0.0, ANGLEUNIT["Degree", 0.0174532925199433]],
      PARAMETER["Standard_Parallel_1", 0.0, ANGLEUNIT["Degree", 0.0174532925199433]],
      PARAMETER["Auxiliary_Sphere_Type", 0.0]],
     CS[Cartesian, 2],
     AXIS["Easting (X)", east, ORDER[1]],
     AXIS["Northing (Y)", north, ORDER[2]],
     LENGTHUNIT["Meter", 1.0]]
  */

  // You can create a spatial reference with the Esri WKT string or the OCG WKT2 string
  sr = SpatialReferenceBuilder.CreateSpatialReference(wkt2);

  // Get OGC WKT2 including authority in top-level objects
  // In this case the authority is written as ID["EPSG",3857]
  wkt2 = sr.GetWkt2(WktFormatMode.AuthorityTop);
  /*  
    PROJCRS["WGS_1984_Web_Mercator_Auxiliary_Sphere",
     BASEGEOGCRS["GCS_WGS_1984",
     DYNAMIC[FRAMEEPOCH[1990.5],MODEL["AM0-2"]],
     DATUM["D_WGS_1984",
      ELLIPSOID["WGS_1984",6378137.0,298.257223563,LENGTHUNIT["Meter",1.0]]],
     PRIMEM["Greenwich",0.0,ANGLEUNIT["Degree",0.017453292519943295]],
     CS[ellipsoidal,2],
     AXIS["Latitude (lat)",north,ORDER[1]],
     AXIS["Longitude(lon)",east,ORDER[2]],
     ANGLEUNIT["Degree",0.017453292519943295]],
     CONVERSION["Mercator_Auxiliary_Sphere",
      METHOD["Mercator_Auxiliary_Sphere"],
      PARAMETER["False_Easting",0.0,LENGTHUNIT["Meter",1.0]],
      PARAMETER["False_Northing",0.0,LENGTHUNIT["Meter",1.0]],
      PARAMETER["Central_Meridian",0.0,ANGLEUNIT["Degree",0.017453292519943295]],
      PARAMETER["Standard_Parallel_1",0.0,ANGLEUNIT["Degree",0.017453292519943295]],
      PARAMETER["Auxiliary_Sphere_Type",0.0]],
      CS[Cartesian,2],
      AXIS["Easting (X)",east,ORDER[1]],
      AXIS["Northing (Y)",north,ORDER[2]],
      LENGTHUNIT["Meter",1.0],
      ID["EPSG",3857]]
  */

  // Get OGC WKT2 including authority in all objects
  // Authority is written as ID["ESPG",<id>] or ID["Esri",<id>]
  wkt2 = sr.GetWkt2(WktFormatMode.AuthorityAll);
  /*
    PROJCRS["WGS_1984_Web_Mercator_Auxiliary_Sphere",
     BASEGEOGCRS["GCS_WGS_1984",
      DYNAMIC[FRAMEEPOCH[1990.5],MODEL["AM0-2"]],
      DATUM["D_WGS_1984",
       ELLIPSOID["WGS_1984",6378137.0,298.257223563,LENGTHUNIT["Meter",1.0,ID["EPSG",9001]],ID["EPSG",7030]],
       ID["EPSG",6326]],
      PRIMEM["Greenwich",0.0,ANGLEUNIT["Degree",0.017453292519943295,ID["EPSG",9102]],ID["EPSG",8901]],
      CS[ellipsoidal,2],
      AXIS["Latitude (lat)",north,ORDER[1]],
      AXIS["Longitude(lon)",east,ORDER[2]],
      ANGLEUNIT["Degree",0.017453292519943295,ID["EPSG",9102]],ID["EPSG",4326]],
      CONVERSION["Mercator_Auxiliary_Sphere",
       METHOD["Mercator_Auxiliary_Sphere",ID["Esri",43104]],
       PARAMETER["False_Easting",0.0,LENGTHUNIT["Meter",1.0,ID["EPSG",9001]],ID["Esri",100001]],
       PARAMETER["False_Northing",0.0,LENGTHUNIT["Meter",1.0,ID["EPSG",9001]],ID["Esri",100002]],
       PARAMETER["Central_Meridian",0.0,ANGLEUNIT["Degree",0.017453292519943295,ID["EPSG",9102]],ID["Esri",100010]],
       PARAMETER["Standard_Parallel_1",0.0,ANGLEUNIT["Degree",0.017453292519943295,ID["EPSG",9102]],ID["Esri",100025]],
       PARAMETER["Auxiliary_Sphere_Type",0.0,ID["Esri",100035]]],
      CS[Cartesian,2],
      AXIS["Easting(X)",east,ORDER[1]],
      AXIS["Northing (Y)",north,ORDER[2]],
      LENGTHUNIT["Meter",1.0,ID["EPSG",9001]],
      ID["EPSG",3857]]
  */
}