IBMDSwitcherKeyPatternParameters

Please tell me how to use IBMDSwitcherKeyPatternParameters in c #

Assuming you have got your "key" object. This is one way of setting the pattern

BMDSwitcherAPI.IBMDSwitcherKeyPatternParameters k_params =
(BMDSwitcherAPI.IBMDSwitcherKeyPatternParameters)key;

k_params.SetPattern(_BMDSwitcherPatternStyle.bmdSwitcherPatternStyleLeftToRightBar);