The water-inlet valve lets water enter the machine. If this valve is defective, you need to completely replace it. It's usually located behind the lower access panel on the left or right side. It's the device with the main water line (usually copper) from the house, a rubber tube to the dishwasher, and two wires attached to it.
The float switch is a small electrical switch that's located right below the dishwasher "floor." Above the switch, on the inside of the dishwasher, is a plastic cylinder that floats up as water fills the dishwasher. If this switch is defective, or if the plastic float gets caught or trapped in the raised position, the water can't enter the dishwasher. If the float switch is defective, you need to replace it.
For the correct parts please list your model number.