Web API 2:[必填]值类型? [英] Web Api 2: [Required] for value types?

问题描述

仅在Web Api输入模型中使用[Required]数据注释似乎会检查实例化为null的引用类型:

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; }
}

在没有默认实例化的情况下，如何使它与值类型一起使用?

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; }
}

使用Nullable<Double>是唯一的方法吗?我们不能创建一些自定义验证属性吗?

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

推荐答案

这是必需属性在内部工作的方式.

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;
    }

所以与0值无关，因此必须使用Range属性进行检查

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

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