Seasoning is a polymer which gives it very strong resistance, which is not going to breakdown just with one dishwasher wash.
The seasoned surface is hydrophobic and highly attractive to oils and fats used for cooking (oleophilic).
The protective layer itself is not very susceptible to soaps, and many users do briefly use detergents and soaps.[28]
Unless you are dish washing it everyday and refuse to dry/reseason it, you will be fine.
However, cast iron is very prone to rust, and the protective layer may have pinholes, so soaking for long periods is contraindicated as the layer may start to flake off.
Seasoning is a polymer which gives it very strong resistance, which is not going to breakdown just with one dishwasher wash.
Unless you are dish washing it everyday and refuse to dry/reseason it, you will be fine.
https://en.m.wikipedia.org/wiki/Seasoning_(cookware)