Web Api 2: [Required] for value types?

问题

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?

回答1:

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

回答2:

you can use the range attribute.

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

回答3:

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

来源：https://stackoverflow.com/questions/31947065/web-api-2-required-for-value-types