C# Check if a decimal has more than 3 decimal places?

Question

I have a situation that I cannot change: one database table (table A) accepts 6 decimal places, while a related column in a different table (table B) only has 3 decimal plac

Answer 1

could you convert it to a string and just do a len function or would that not cover your situation?

follow up question: would 300.4 be ok?