Program.cs

using System.ComponentModel.DataAnnotations;

namespace RequiredIf
{
    class Program
    {
        static void Main(string[] args)
        {
            // Scenario 0: Condition met, Surname is null, Name is null (validation should fail)
            Person test0 = new Person();
            ValidateModel(test0);

            // Scenario 1: Condition met, Surname is empty, Name is null (validation should fail)
            Person test1 = new Person { Surname = "" };
            ValidateModel(test1);

            // Scenario 2: Condition met, Surname is empty, Name is set (validation should pass)
            Person test2 = new Person
            {
                Surname = "",
                Name = "John"
            };
            ValidateModel(test2);

            // Scenario 3: Condition met, Surname is not empty, Name is null (validation should pass)
            Person test3 = new Person
            {
                Surname = "Doe"
            };
            ValidateModel(test3);

            // Scenario 4: Condition met, Surname is not empty, Name is set (validation should pass)
            Person test4 = new Person
            {
                Surname = "Doe",
                Name = "John"
            };
            ValidateModel(test4);

            // Scenario 5: Condition not met, Surname is empty, Name is null (validation should pass)
            TestWithoutCondition test5 = new TestWithoutCondition { Surname = "" };
            ValidateModel(test5);

            // Scenario 6: Condition not met, Surname is empty, Name is set (validation should pass)
            Student teststudent1 = new Student
            {
                Surname = "",
                Name = "John"
            };
            ValidateModel(teststudent1);

            // Scenario 7: Condition not met, Surname is not empty, Name is null (validation should pass)
            TestWithoutCondition test7 = new TestWithoutCondition
            {
                Surname = "Doe"
            };
            ValidateModel(test7);

            // Scenario 8: Condition not met, Surname is not empty, Name is set (validation should pass)
            NestedHierarchyTest test8 = new NestedHierarchyTest
            {
                Surname = "Doe",
                Name = "John"
            };
            ValidateModel(test8);

            // Scenario 8: Condition not met, Surname is not empty, Name is set (validation should pass)
            Student teststudent2 = new Student
            {
                Surname = "Doe",
                Name = "John",
                StudentId = "HD723IKK"
            };
            ValidateModel(teststudent2);

            Person test = new Person
            {
                Surname = "  ", // Inválido
                Name = null    // Inválido porque Surname está vacío
            };

            Console.WriteLine("\nSINGLE VALIDATION TEST: \n.");

            // Validar el modelo
            test.ValidateSelf();

            // Verificar errores
            if (test.HasErrors)
            {
                foreach (var error in test.GetErrors(null))
                {
                    Console.WriteLine($"Error: {error}");
                }
            }
            else
            {
                Console.WriteLine("All validations passed.");
            }

            Console.WriteLine("Validation completed.");
        }


        private static void ValidateModel(object model)
        {
            Console.WriteLine($"Validating model: {model.GetType().Name}");

            var context = new ValidationContext(model);
            var results = new List<ValidationResult>();

            bool isValid = Validator.TryValidateObject(model, context, results, true);

            if (isValid)
            {
                Console.WriteLine("Model is valid.");
            }
            else
            {
                Console.WriteLine("Model validation failed.");
                foreach (var validationResult in results)
                {
                    Console.WriteLine($" - {validationResult.ErrorMessage}");
                }
            }

            Console.WriteLine();
        }
    }

    public class TestWithoutCondition : Person
    {
 
    }

    public class NestedHierarchyTest : Student
    {

    }

}