public class BasicMaterial : Material 

var sr = MapView.Active.Map.SpatialReference;

var extent = MapView.Active.Extent;
var center = extent.Center;
var centerZ = MapPointBuilderEx.CreateMapPoint(center.X, center.Y, 500, sr);

// cube
multipatch = ArcGIS.Core.Geometry.MultipatchBuilderEx.CreateMultipatch(MultipatchConstructType.Cube, centerZ, 200, sr);
// tetrahedron
multipatch = ArcGIS.Core.Geometry.MultipatchBuilderEx.CreateMultipatch(MultipatchConstructType.Tetrahedron, centerZ, 200, sr);
// diamond
multipatch = ArcGIS.Core.Geometry.MultipatchBuilderEx.CreateMultipatch(MultipatchConstructType.Diamond, centerZ, 200, sr);
// hexagon
multipatch = ArcGIS.Core.Geometry.MultipatchBuilderEx.CreateMultipatch(MultipatchConstructType.Hexagon, centerZ, 200, sr);

// sphere frame
multipatch = ArcGIS.Core.Geometry.MultipatchBuilderEx.CreateMultipatch(MultipatchConstructType.SphereFrame, centerZ, 200, 0.8, sr);
// sphere
multipatch = ArcGIS.Core.Geometry.MultipatchBuilderEx.CreateMultipatch(MultipatchConstructType.Sphere, centerZ, 200, 0.8, sr);
// cylinder
multipatch = ArcGIS.Core.Geometry.MultipatchBuilderEx.CreateMultipatch(MultipatchConstructType.Cylinder, centerZ, 200, 0.8, sr);
// cone
multipatch = ArcGIS.Core.Geometry.MultipatchBuilderEx.CreateMultipatch(MultipatchConstructType.Cone, centerZ, 200, 0.8, sr);


// use the builder to add materials or textures
//   - create a cone with a material
builder = new MultipatchBuilderEx(MultipatchConstructType.Cone, centerZ, 200, 0.8, sr);

BasicMaterial faceMaterial = new BasicMaterial();
faceMaterial.Color = System.Windows.Media.Color.FromRgb(255, 0, 0);
faceMaterial.Shininess = 150;
faceMaterial.TransparencyPercent = 50;
faceMaterial.EdgeWidth = 20;

foreach (var patch in builder.Patches)
  patch.Material = faceMaterial;

multipatch = builder.ToGeometry() as Multipatch;