The aim of the proposed experiment is to study the anisotropy of the magnetic resonance peak in (Ba1-xKx)Fe2As2 using polarized neutrons with longitudinal polarization analysis. Two recent publications report contradicting results concerning this topic. In electron-doped Ba(Fe1-xNix)2As2 a strong anistropy has been found where only the in-plane component of the spin fluctuation contributes to the magnetic signal. In FeTe0.5Se0.5 the magnetic resonance has been found to be more isotropic, where the in-plane component is only 20% stronger than the out-of-plane component, which fits better into the picture of the magnetic resonance being a singlet-triplet excitation of the Cooper pairs. In light of these contradicting results we want to study the anisotropy of the magnetic resonance in hole-doped (Ba1-xKx)Fe2As2, a good and very clean candidate due to its structurally unchanged FeAs layers.