Nanoscale C and SiC doped MgB2 tapes were prepared by the in situ powder-in-tube method. The samples were characterized using X-ray diffraction, scanning electron microscope, superconducting quantum interference device magnetometer etc. Transport JC and its magnetic field dependence were evaluated by a standard four-probe technique. It is found that JC for all the C and SiC doped tapes was significantly enhanced in magnetic fields up to 14 T compared to the undoped ones. For the 5% C and SiC doped samples, at 4.2 K and 10 T, JC increased by a factor of 32 and 26, respectively. The improvement of JC-B properties in C and SiC doped MgB2 tapes is attributed to good grain linkage and the introduction of effective flux pining centers with the doping. Furthermore, our results clearly prove that the observed positive effects after mixing with SiC are nothing else than the result of the decomposition of this compound and substitution of carbon for B in MgB2.