Question

CustomerValidator: AbstractValidator<Customer> 

How might one dynamically instantiate the class above if passed an instance of a Customer?? Similarly if I had:

Cat c = new Cat(); 

I would want to dynamically invoke the class that implements

AbstractValidator<Cat> 

Answer 1

One common approach (if you own both Customer and CustomerValidator) is to decorate the class with the class that provides validation, via an attribute:

[Validator(typeof(CustomerValidator))] public class Customer { } 

Note that you may find it easier to work outside of generics, perhaps via an interface (note: no methods etc shown here):

public interface IValidator { } public class CustomerValidator : AbstractValidator<Customer> {} public class AbstractValidator<T> : IValidator where T : class {} 

Then obtain the correct validator via reflection:

[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = true)] public sealed class ValidatorAttribute : Attribute {     public Type ValidatorType { get; private set; }     public ValidatorAttribute(Type validatorType)     {         ValidatorType = validatorType;     }     public static IValidator GetValidator(object obj)     {         if (obj == null) return null;         return GetValidator(obj.GetType());     }     public static IValidator GetValidator(Type type)     {         if (type == null) return null;         ValidatorAttribute va = (ValidatorAttribute)             Attribute.GetCustomAttribute(type, typeof(ValidatorAttribute));         if (va == null || va.ValidatorType == null) return null;         return (IValidator) Activator.CreateInstance(va.ValidatorType);     } } 

So calling GetValidator should return null or a suitable IValidator.

You can use generics in the above – but it usually creates more problems than it solves in example like this.