Web Api 2: [Required] for value types?

Question

Using the [Required] data annotation in Web Api input models only seems to check for reference types being instantiated to null:

public class MyInputModel
{
    [Required] // This works! ModelState fails.
    public CustomClass MyCustomProperty { get; set; }
}

How can we get this to work with value types WITHOUT the default instantiation?

public class MyInputModel
{
    [Required] // This is ignored because MyDouble is defaulted to 0
    public double MyDouble { get; set; }
}

Is the only way through using Nullable<Double>? Could we not create some custom validation attribute?

You can always write custom validation attribute. E.g http://www.codeproject.com/Articles/260177/Custom-Validation-Attribute-in-ASP-NET-MVC — vijay shiyani, Aug 12 '15 at 12:53

score 4 · Answer 1 · answered Aug 11 '15 at 16:39

4

you can use the range attribute.

[Range(0, 99)]
public double MyDouble { get; set; }

answered Aug 11 '15 at 16:39

Yousuf

3,105
7
28
38

1

Except that in my case, a value of 0 isn't the same as no value. 0 is still valid. – Dave New Aug 11 '15 at 17:02

score 3 · Answer 2 · answered Aug 12 '15 at 12:09

3

try making value type Nullable e.g. public double? MyDouble { get; set; }

answered Aug 12 '15 at 12:09

vijay shiyani

766
7
19

score 1 · Accepted Answer · answered Aug 12 '15 at 11:59

This is how the required attribute working internally.

 override bool IsValid(object value) {
        if (value == null) {
            return false;
        }

        // only check string length if empty strings are not allowed
        var stringValue = value as string;
        if (stringValue != null && !AllowEmptyStrings) {
            return stringValue.Trim().Length != 0;
        }

        return true;
    }

So nothing to do with the 0 value so you must check it with Range attribute

Web Api 2: [Required] for value types?

3 Answers3

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