public bool IsMaterialTextured( 
   int materialIndex
)

{
  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);
}

{
  if (multipatch.HasMaterials)
  {
    int patchIndex = 0;
    // Get the material index for the specified patch.
    int materialIndex = multipatch.GetPatchMaterialIndex(patchIndex);

    System.Windows.Media.Color color = multipatch.GetMaterialColor(materialIndex);
    int tranparencyPercent = multipatch.GetMaterialTransparencyPercent(materialIndex);
    bool isBackCulled = multipatch.IsMaterialCullBackFace(materialIndex);

    if (multipatch.IsMaterialTextured(materialIndex))
    {
      int bpp = multipatch.GetMaterialTextureBytesPerPixel(materialIndex);
      int columnCount = multipatch.GetMaterialTextureColumnCount(materialIndex);
      int rowCount = multipatch.GetMaterialTextureRowCount(materialIndex);
    }
  }
}