Use a guard clause to enforce input validation rules in C# Input validation enables you ... clauses throw exceptions to terminate the flow of control of a program, and you want to avoid throwing ...

Attributes that affect compiled code aren’t a new thing for C#, so this would align with existing patterns. And if we ever get declarative parameter validation, it would look something like this.

no client-side validation happens. Other forums suggest copying the aspnet_client folder to the project root, but, on my machine, C Inetpub\wwwroot\aspnet_client\system_web\4_0_30319 is empty.