Asp Core: Adding Attribute will prevent the debug session from continuing

I created an interest rate calculator however I modified the class to specify required and range attributes. When I add them and change my variables to null I receive the error: "Adding Attribute Error

This is the FutureValueModel.cs class producing the errors:

 public class FutureValueModel
    {
        [Required(ErrorMessage = "Please enter a monthly investment.")]
        [Range(1, 500, ErrorMessage =
               "Monthly investment amount must be between 1 and 500.")]
        public decimal? MonthlyInvestment { get; set; }

        [Required(ErrorMessage = "Please enter a yearly interest rate.")]
        [Range(0.1, 10.0, ErrorMessage =
               "Yearly interest rate must be between 0.1 and 10.0.")]
        public decimal? YearlyInterestRate { get; set; }

        [Required(ErrorMessage = "Please enter a number of years.")]
        [Range(1, 50, ErrorMessage =
               "Number of years must be between 1 and 50.")]
        public int? Years { get; set; }