C# Script Component error about lambda expression

When I write this in the C# Script Component to define a method in a custom class using lambda expression, it gives me some errors.

But when I don’t use lambda expression or use lambda expression to do other things it seems ok.

I want to know the reason. Thank you!

Lambda expressions for methods, i.e. “Expression-bodied members” are a new C# feature, available since C# 7.0, released in March, 2017. It is likely that C# 7 features are not supported (yet).

Oh, thank you very much for your patient explanation. I understand now~