Model Validation using Fluent Validation on WEB API

Question

I am trying to use fluent validation for my models on Web API project. I have two classes name OrderHeader and Items . And i have property name as OrderQty on Items class which is an integer and i have applied a rule for OrderQty as it should be number only (i.e. 0-9) . whenever i get the JSON request for OrderQty as alphanumeric (like 1A) i cannot serialize the JSON and could not get the errormessage from fluent validation on Modelstate . How to achieve this could someone help me on this please ? Thanks in advance !!!

I have tried to convert the OrderQty to ToString() and applied rule but i could not get the errormessage while serialiaing the JSON .

My modal classes :

public class OrderHeader
{
    public string OrderNumber { get; set; }
    public string Address1 { get; set; }
    public string Address2 { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string Zip { get; set; }
    public string Phone { get; set; }
    public string Created { get; set; }
    public List<Items> Items { get; set; }
}

public class Items
{
   public string ItemNumber { get; set; }
   public string Description { get; set; }
   public int OrderQty { get; set; }
   public double Weight { get; set; }
   public double Price { get; set; }
   public string Status { get; set; }
}

Fluent Validations

public class OrderHeaderValidator : AbstractValidator<OrderHeader>
{

    public OrderHeaderValidator()
    {
        RuleFor(x => x.OrderNumber.Trim()).NotEmpty().WithMessage("OrderNumber : cannot be blank.").Length(1, 6).WithMessage("OrderNumber : cannot be more than 6 characters.").Matches("^[0-9]*$").WithMessage("OrderNumber : must contains only numbers");
        RuleFor(x => x.Items).SetCollectionValidator(new ItemValidator());
    }
}


public class ItemsValidator : AbstractValidator<Items>
{

    public ItemsValidator()
    {
        RuleFor(x => x.OrderQty.ToString()).NotNull().WithMessage("TotalOrderQuantity : cannot be blank").Matches("^[0-9]*$").WithMessage("TotalOrderQuantity : must contains only numbers");
        RuleFor(x => x.Status.ToUpper()).NotEmpty().WithMessage("Status : Provide the Status").Length(0, 1).WithMessage("Status : cannot be more than 1 character").Matches("O").WithMessage("Status : Must be 'O'");

    }

}

Serializing and getting error message :

 string errors = JsonConvert.SerializeObject(ModelState.Values
                .SelectMany(state => state.Errors)
                .Select(error => error.ErrorMessage));

I expect the output should be if the value for is 1A from JSON request then it displays the error message as:

TotalOrderQuantity : must contains only numbers

Maxim Tkachenko · Accepted Answer · 2019-05-16 09:05:56Z

1

You can't deserialize 1A into int OrderQty. Use string OrderQty instead and check .Must(x => int.TryParse(x.OrderQty, out _)) in validator.

It's OK that your API has specification like OrderQty must be integer - int OrderQty. If someone tries to send string instead of integer - you can catch deserializion exception and reject the request with message like invalid request: ...

edited May 16, 2019 at 9:05

answered May 16, 2019 at 7:36

Maxim Tkachenko

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10 Comments

Vicky Over a year ago

I used like RuleFor(x=>x.OrderQty).Must(validateint).WithMessage("Must be integer"); And my validateint function is like public bool validateint(string value) { int number; bool a = int.TryParse(value, out number); return a; } Its works great !!! but how can i show the errormessage as which item having an invalid OrderQty in a list of items in the model

Vicky Over a year ago

Like how can i append the ItemNumber in Error Message . I tried below, RuleFor(m => new { m.OrderQty, m.ItemNumber }).Must(x => validateint(x.OrderQty, x.ItemNumber)) .WithMessage(string.Format("A {0}",x.ItemNumber)); But i could not make it success

Maxim Tkachenko Over a year ago

@Vicky Try this .WithMessage(x => $"A{x.ItemNumber}")

Vicky Over a year ago

I am getting the compile time errors like Unexpected character '$' and some errors

Vicky Over a year ago

I uesed like this RuleFor(m => new { m.OrderQty, m.ItemNumber }).Must(x => validateint(x.OrderQty, x.ItemNumber)).WithMessage(x => $"A{x.ItemNumber}");

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