How to do Integer model validation in asp.net mvc 2

Question

I have a registration form and the user must enter the square footage of their house. I would like this value to be only an integer. Is there a way to validate this value using attributes asp.net mvc?

Answer 1

yes, it is, but you will have to make a flat version of the object you are wanting to create, because the validation with attributes only runs AFTER MVC has converted your data into the model. which, when your value is an int, will fail to validate if the user did not enter an int, and you will get a MVC error message in stead of your errormessage.

can you post the object you are wanting to make?

with a flat version i mean all datetimes and ints are stings in the flat version.

then i use this:

    [DisplayName("Square meters")]
    [PosNumberNoZero(ErrorMessage = "need a positive number, bigger than 0")]
    public string squaremeters { get; set; }

in the same file

public class PosNumberNoZeroAttribute : ValidationAttribute {
    public override bool IsValid(object value) {
        if (value == null) {
            return true;
        }
        int getal;
        if (int.TryParse(value.ToString(), out getal)) {

            if (getal == 0)
                return false;

            if (getal > 0)
                return true;
        }
        return false;

    }
}

if my modelstate is valid then, i use AutoMapper to convert my FlatModel into my Model, which is just 2 lines of code.

edit: if 0 is a valid number:

public class PosNumberAttribute : ValidationAttribute {
    public override bool IsValid(object value) {
        if (value == null) {
            return true;
        }
        int getal;
        if (int.TryParse(value.ToString(), out getal)) {

            if (getal >= 0)
                return true;
        }
        return false;
    }
}

Answer 2

Realise this has already been answered, but Stefanvds' answer is uneccessarily complicated. Just use MVCs built in validation attributes:

[DisplayName("Square Feet")]
[Required(ErrorMessage = "Square Feet is Required")]
[Range(0, int.MaxValue, ErrorMessage = "Square Feet must be a positive number")]
public int SquareFeet { get; set; }

Answer 3

I usually use the range attribute like this:

Positive int:

[Range(0,int.MaxValue)]
public int Id { get; set; }

Negative int:

[Range(int.MinValue,-1)]
public int Id { get; set; }

Any int:

[Range(int.MinValue,int.MaxValue)]
public int Id { get; set; }

Answer 4

Well using Range for an int field will not work if you have some letters like "a".
The error Handler is not called (ASP.NET CORE 1.0 RC2).