How to loop through a static class of constants?

Using Reflection you can find all constant values in the class:

var values = typeof(Parent.Child).GetFields(BindingFlags.Static | BindingFlags.Public)
                                 .Where(x => x.IsLiteral && !x.IsInitOnly)
                                 .Select(x => x.GetValue(null)).Cast<string>();

Then you can check if values contains something:

if(values.Contains("something")) {/**/}