通过自定义DataAnnotationsModelMetadataProvider添加StringLengthAttribute

时间:2012-10-21 13:26:07

标签: c# asp.net-mvc

我需要在现有的ASP.NET MVC 4项目中为许多模型添加StringLengthAttribute验证,并尝试通过我自己的DataAnnotationsModelMetadataProvider派生的模型元数据提供程序自动执行此操作。

它与RequiredAttribute和其他一些数据注释属性完美配合(我得到了客户端和服务器端验证工作),但是没有添加对字符串长度的验证 - 找到下面的最小示例。 / p>

public class CustomModelMetadataProvider : DataAnnotationsModelMetadataProvider
{
    protected override ModelMetadata CreateMetadata(IEnumerable<Attribute> attributes,
                                                    Type containerType,
                                                    Func<object> modelAccessor,
                                                    Type modelType,
                                                    string propertyName)
    {
        StringLengthAttribute lengthAttribute = new StringLengthAttribute(256);
        attributes = attributes.Union(new[] { lengthAttribute });
        return base.CreateMetadata(attributes,
                                   containerType,
                                   modelAccessor,
                                   modelType,
                                   propertyName);
    }
}

所以看起来像StringLengthAttribute它以某种特殊方式处理。关于如何使其工作或更好的实施想法的任何想法?

1 个答案:

答案 0 :(得分:1)

玩完之后,我无法触发StringLength属性。

不理想,但我想另一种解决方案是使用全局ModelValidatorProvider类。当然,你不会得到StringLengthAttribute提供的内置Javascript,你会编写自己的逻辑,但它可以快速解决你以后可以解决的问题吗?

    public class MyCustomModelValidatorProvider : ModelValidatorProvider
{
    public override IEnumerable<ModelValidator> GetValidators(ModelMetadata metadata, ControllerContext context)
    {
        return new List<ModelValidator>() { new MyCustomModelValidator(metadata, context) };
    }

    public class MyCustomModelValidator : ModelValidator
    {
        public MyCustomModelValidator(ModelMetadata metadata, ControllerContext context)
            : base(metadata, context)
        {   }

        public override IEnumerable<ModelValidationResult> Validate(object container)
        {
            var model = this.Metadata.Model; 
            if (model is string)
            {
                var value = model as string;

                if (String.IsNullOrEmpty(value) || value.Length > 256)
                {
                    var validationResult = new ModelValidationResult();
                    validationResult.Message = (this.Metadata.DisplayName ?? this.Metadata.PropertyName) 
                        + " needs to be no more then 256 characters";

                    return new List<ModelValidationResult>() { validationResult };
                }
            }

            return new List<ModelValidationResult>();
        }
    }

}

将MyCustomModelValidator添加到Global.asax

中的集合
        protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();

        // Use LocalDB for Entity Framework by default
        Database.DefaultConnectionFactory = new SqlConnectionFactory(@"Data Source=(localdb)\v11.0; Integrated Security=True; MultipleActiveResultSets=True");

        RegisterGlobalFilters(GlobalFilters.Filters);
        RegisterRoutes(RouteTable.Routes);


        ModelValidatorProviders.Providers.Add(new MyCustomModelValidatorProvider());
    }