Validate a signup form in C#
C# interview exercise on Practical, difficulty 2 of 3. Solve it in the editor beside a worked example; the tests run the moment you do.
Write ValidateSignup(name, email, age) that returns a list of every problem, in this order, and an empty list when all is well: "name is required" (blank name), "email is invalid" (use the given IsEmail), "must be at least 13".
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Progress is saved in your browser, and in your account if you sign in.