Dielectric nanophotonics is the modern and very relevant field of optics. In this work we use the recently reported Cartesian multipole decomposition approach for all-dielectric metasurfaces [1] to study optical properties of the silicon metasurface at the nanoscale. This metasurface consists of crystalline silicon cubes rotated by 45° around the axis perpendicular to the surface plane. We use numerical modeling and semi-analytical approach to find origins of the scatering by the considered metasurface. Results obtained with the multipole approach are in the good agreement with the direct calculations of transmission and reflection spectra. Insights from our study can be widely used to design novel metasurfaces and metadevices and tune their optical properties to achieve a needed functionality.