c# - ASP.NET MVC : Custom Validation by DataAnnotation

Question

我有一个具有 4 个字符串类型属性的模型。我知道您可以使用 StringLength 注释来验证单个属性的长度。但是我想验证 4 个属性的组合长度。

使用数据注释执行此操作的 MVC 方法是什么？

我问这个是因为我是 MVC 的新手，想在制定自己的解决方案之前以正确的方式进行操作。

Answer 1

您可以编写自定义验证属性:

public class CombinedMinLengthAttribute: ValidationAttribute
{
    public CombinedMinLengthAttribute(int minLength, params string[] propertyNames)
    {
        this.PropertyNames = propertyNames;
        this.MinLength = minLength;
    }

    public string[] PropertyNames { get; private set; }
    public int MinLength { get; private set; }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var properties = this.PropertyNames.Select(validationContext.ObjectType.GetProperty);
        var values = properties.Select(p => p.GetValue(validationContext.ObjectInstance, null)).OfType<string>();
        var totalLength = values.Sum(x => x.Length) + Convert.ToString(value).Length;
        if (totalLength < this.MinLength)
        {
            return new ValidationResult(this.FormatErrorMessage(validationContext.DisplayName));
        }
        return null;
    }
}

然后你可能有一个 View 模型并用它装饰它的一个属性:

public class MyViewModel
{
    [CombinedMinLength(20, "Bar", "Baz", ErrorMessage = "The combined minimum length of the Foo, Bar and Baz properties should be longer than 20")]
    public string Foo { get; set; }
    public string Bar { get; set; }
    public string Baz { get; set; }
}