public TextureCompressionType GetMaterialTextureCompressionType( 
   int materialIndex
)

{
  int patchIndex = 0;

  // standard geometry properties
  bool hasZ = multipatch.HasZ;
  bool hasM = multipatch.HasM;
  bool hasID = multipatch.HasID;
  bool isEmpty = multipatch.IsEmpty;
  var sr = multipatch.SpatialReference;

  // number of patches (parts)
  int patchCount = multipatch.PartCount;
  // number of points
  int pointCount = multipatch.PointCount;

  // retrieve the points as MapPoints
  ReadOnlyPointCollection pointsMultipatch = multipatch.Points;
  // or as 3D Coordinates
  IReadOnlyList<Coordinate3D> coordinates = multipatch.Copy3DCoordinatesToList();


  // multipatch materials
  bool hasMaterials = multipatch.HasMaterials;
  int materialCount = multipatch.MaterialCount;


  // multipatch textures
  bool hasTextures = multipatch.HasTextures;
  int textureVertexCount = multipatch.TextureVertexCount;

  // normals
  bool hasNormals = multipatch.HasNormals;


  // properties for an individual patch (if multipatch.PartCount > 0)
  int patchPriority = multipatch.GetPatchPriority(patchIndex);
  PatchType patchType = multipatch.GetPatchType(patchIndex);

  // patch points
  int patchPointCount = multipatch.GetPatchPointCount(patchIndex);
  int pointStartIndex = multipatch.GetPatchStartPointIndex(patchIndex);
  // the patch Points are then the points in multipatch.Points from pointStartIndex to pointStartIndex + patchPointCount 

  // if the multipatch has materials 
  if (hasMaterials)
  {
    // does the patch have a material?  
    //   materialIndex = -1 if the patch does not have a material; 
    //   0 <= materialIndex < materialCount if the patch does have materials
    int materialIndex = multipatch.GetPatchMaterialIndex(patchIndex);


    // properties for an individual material (if multipatch.MaterialCount > 0)
    var color = multipatch.GetMaterialColor(materialIndex);
    var edgeColor = multipatch.GetMaterialEdgeColor(materialIndex);
    var edgeWidth = multipatch.GetMaterialEdgeWidth(materialIndex);
    var shiness = multipatch.GetMaterialShininess(materialIndex);
    var percent = multipatch.GetMaterialTransparencyPercent(materialIndex);
    var cullBackFace = multipatch.IsMaterialCullBackFace(materialIndex);

    // texture properties
    bool isTextured = multipatch.IsMaterialTextured(materialIndex);
    if (isTextured)
    {
      int columnCount = multipatch.GetMaterialTextureColumnCount(materialIndex);
      int rowCount = multipatch.GetMaterialTextureRowCount(materialIndex);
      int bpp = multipatch.GetMaterialTextureBytesPerPixel(materialIndex);
      TextureCompressionType compressionType = multipatch.GetMaterialTextureCompressionType(materialIndex);
      var texture = multipatch.GetMaterialTexture(materialIndex);
    }
  }

  // texture coordinates (if multipatch.HasTextures = true)
  if (hasTextures)
  {
    int numPatchTexturePoints = multipatch.GetPatchTextureVertexCount(patchIndex);
    var coordinate2D = multipatch.GetPatchTextureCoordinate(patchIndex, 0);

    ICollection<Coordinate2D> textureCoordinates = new List<Coordinate2D>(numPatchTexturePoints);
    multipatch.GetPatchTextureCoordinates(patchIndex, ref textureCoordinates);
  }


  // patch normals (if multipatch.HasNormals = true)
  if (hasNormals)
  {
    //  number of normal coordinates = multipatch.GetPatchPointCount(patchIndex)
    Coordinate3D patchNormal = multipatch.GetPatchNormal(patchIndex, 0);
    ICollection<Coordinate3D> normalCoordinates = new List<Coordinate3D>(patchPointCount);
    multipatch.GetPatchNormals(patchIndex, ref normalCoordinates);
  }
}

{
  int patchIndex = 0;
  int materialIndex = multipatch.GetPatchMaterialIndex(patchIndex);
  if (!multipatch.IsMaterialTextured(materialIndex))
    return;

  TextureCompressionType compressionType =
    multipatch.GetMaterialTextureCompressionType(materialIndex);

  string ext = compressionType == TextureCompressionType.CompressionJPEG ? ".jpg" : ".dat";
  byte[] textureBuffer = multipatch.GetMaterialTexture(materialIndex);

  Stream imageStream = new MemoryStream(textureBuffer);
  System.Drawing.Image image = System.Drawing.Image.FromStream(imageStream);
  image.Save(@"C:\temp\myImage" + ext);
}