Why is Asp.Net Core's built in validation error message showing instead of my Fluent Validation one?

Question

I thought this was going to be pretty straight forward...

I have this decimal property:

[Column(TypeName = "decimal(18,2)")]
public decimal ProjectBudget { get; set; }

I want to validate the input to be a positive number. These are the two rules I have tried:

RuleFor(x => x.ProjectBudget.ToString())
    .Matches("^[0-9]*$").WithMessage("Only positive numbers, please.");

RuleFor(x => x.ProjectBudget)
    .GreaterThanOrEqualTo(0).WithMessage("Only positive numbers, please.");

In both cases, if I enter "sdfhj", this is the error message I get:

The value 'sdfhj' is not valid for ProjectBudget.

That's the error message from Asp.Net Core's built in validation.

Why doesn't my error message "Only positive numbers, please." appear?

(I know I can specify the error message on the property using something like [Range(0, (double)decimal.MaxValue, ErrorMessage = "Only positive numbers, please.")] , but that's not what I'm asking.)

Answer 1

I think it is because the type of property is decimal and .net core is not accepting the request. Fluent validation even not acting on that.

Answer 2

Try this.

            services.AddControllersWithViews()
               .AddFluentValidation(options =>
                {
                   options.RegisterValidatorsFromAssembly(Assembly.GetEntryAssembly());
                   options.ImplicitlyValidateChildProperties = true;
                   options.RunDefaultMvcValidationAfterFluentValidationExecutes = false;
                });