ASP.NET 动态数据教程－用自定义属性自定义数据字段验证

using System;
using System.Web.DynamicData;
using System.ComponentModel.DataAnnotations;
 
namespace DynamicData
{
    [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false)]
    sealed public class CustomAttribute : ValidationAttribute
    {
        public override bool IsValid(object value)
        {
            bool result = true;
           
            string str = Convert.ToString(value);
            if (str.Length < 3 || str.Length > 20)
            {
                result = false;
            }
           
            return result;
        }
    }
   
   
    [MetadataType(typeof(CompaniesMetadata))]
    partial class Companies
    {
   
    }
   
   
    partial class CompaniesMetadata
    {
        [CustomAttribute(ErrorMessage="Title 的长度是 3-20。")]
        public object Title;
    }
}