C＃属性来检查一个日期是否比其他早期 [英] C# attribute to check whether one date is earlier than the other

问题描述

我有一个视图模型包含两个日期时间的属性我MVC4 Prject：

I have a ViewModel for my MVC4 Prject containing two DateTime properties:

[Required]
[DataType(DataType.Date)]
public DateTime RentDate { get; set; }

[Required]
[DataType(DataType.Date)]
public DateTime ReturnDate { get; set; }

有没有用C＃一个简单的方法属性为 [比较（someProperty）] 来查看天气RentDate属性的值大于ReturnDate的货值？

Is there a simple way to use C# attributes as [Compare("someProperty")] to check weather the value of RentDate property is earlier than the value of ReturnDate?

推荐答案

下面是一个非常快的基本实现（没有错误检查等）应该做你的要求（仅适用于服务器端...它不会做ASP .NET客户端的JavaScript验证）。我没有测试它，但应该足以让你开始。

Here is a very quick basic implementation (without error checking etc.) that should do what you ask (only on server side...it will not do asp.net client side javascript validation). I haven't tested it, but should be enough to get you started.

using System;
using System.ComponentModel.DataAnnotations;

namespace Test
{
   [AttributeUsage(AttributeTargets.Property)]
   public class DateGreaterThanAttribute : ValidationAttribute
   {
      public DateGreaterThanAttribute(string dateToCompareToFieldName)
      {
          DateToCompareToFieldName = dateToCompareToFieldName;
      }

       private string DateToCompareToFieldName { get; set; }

       protected override ValidationResult IsValid(object value, ValidationContext validationContext)
       {
           DateTime earlierDate = (DateTime)value;

           DateTime laterDate = (DateTime)validationContext.ObjectType.GetProperty(DateToCompareToFieldName).GetValue(validationContext.ObjectInstance, null);

           if (laterDate > earlierDate)
           {
               return ValidationResult.Success;
           }
           else
           {
               return new ValidationResult("Date is not later");
           }
       }
   }


   public class TestClass
   {
       [DateGreaterThan("ReturnDate")]
       public DateTime RentDate { get; set; }

       public DateTime ReturnDate { get; set; }
   }
}

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