The description in the link you supplied says it's Active LOW:
"Switch Type: SPDT microswitch, configured for SPST Normally Open behavior. Behavior: When the limit switch is not being pushed in, the sensor maintains a digital HIGH signal on its sensor port. This High signal is coming from the Microcontroller. When an external force (like a collision or being pressed up against a wall) pushes the switch in, it changes its signal to a digital LOW until the limit switch is released. An unpressed switch is indistinguishable from an open port."
This also indicates you need a pull-up resistor. Either mount one externally or use the internal one by changing:
pinMode( LimitSwitch, INPUT);
pinMode( LimitSwitch, INPUT_PULLUP);
If you don't have a pull-up resistor you may get random LOW indications when the switch is not pressed.