How do you get shedinja in Pokemon Diamond?

You can't get Shedinja in Pokemon Diamond. It's only obtainable in Pokemon Ruby, Sapphire, and Emerald by evolving Nincada.

Here's how to get Shedinja in those games:

1. Catch a Nincada: You can find Nincada in the grass in various locations, including the Petalburg Woods.

2. Level it up to level 20: Once Nincada reaches level 20, it will evolve into Ninjask.

3. Have a free slot in your party: Before Nincada evolves, make sure you have an empty slot in your party. This is crucial for getting Shedinja.

4. Level up Nincada to level 20: When Nincada levels up, it will evolve into Ninjask and Shedinja will be automatically added to your party in the free slot.

Note: This method only works once per game. You can only get one Shedinja per game cartridge.