CompareValues标签对Model中的属性进行验证

在Asp.Net MVC中实现CompareValues标签对Model中的属性进行验证

 

在Asp.Net MVC中可以用继承ValidationAttribute的方式，自定制实现Model两个中两个属性值的比较验证

具体应用场景为：要对两个属性值的大小进行验证

代码如下所示：

    /// <summary>

    /// Specifies that the field must compare favourably with the named field, if objects to check are not of the same type

    /// false will be return

    /// </summary>

    public class CompareValuesAttribute : ValidationAttribute

    {

        /// <summary>

        /// The other property to compare to

        /// </summary>

        public string OtherProperty { get; set; }



        public CompareValues Criteria { get; set; }



        /// <summary>

        /// Creates the attribute

        /// </summary>

        /// <param name="otherProperty">The other property to compare to</param>

        public CompareValuesAttribute(string otherProperty, CompareValues criteria)

        {

            if (otherProperty == null)

                throw new ArgumentNullException("otherProperty");



            OtherProperty = otherProperty;

            Criteria = criteria;

        }



        /// <summary>

        /// Determines whether the specified value of the object is valid.  For this to be the case, the objects must be of the same type

        /// and satisfy the comparison criteria. Null values will return false in all cases except when both

        /// objects are null.  The objects will need to implement IComparable for the GreaterThan,LessThan,GreatThanOrEqualTo and LessThanOrEqualTo instances

        /// </summary>

        /// <param name="value">The value of the object to validate</param>

        /// <param name="validationContext">The validation context</param>

        /// <returns>A validation result if the object is invalid, null if the object is valid</returns>

        protected override ValidationResult IsValid(object value, ValidationContext validationContext)

        {

            // the the other property

            var property = validationContext.ObjectType.GetProperty(OtherProperty);



            // check it is not null

            if (property == null)

                return new ValidationResult(String.Format("Unknown property: {0}.", OtherProperty));



            // check types

            var memberName = validationContext.ObjectType.GetProperties().Where(p => p.GetCustomAttributes(false).OfType<DisplayAttribute>().Any(a => a.Name == validationContext.DisplayName)).Select(p => p.Name).FirstOrDefault();

            if (memberName == null)

            {

                memberName = validationContext.DisplayName;

            }

            if (validationContext.ObjectType.GetProperty(memberName).PropertyType != property.PropertyType)

                return new ValidationResult(String.Format("The types of {0} and {1} must be the same.", memberName, OtherProperty));



            // get the other value

            var other = property.GetValue(validationContext.ObjectInstance, null);



            // equals to comparison,

            if (Criteria == CompareValues.EqualTo)

            {

                if (Object.Equals(value, other))

                    return null;

            }

            else if (Criteria == CompareValues.NotEqualTo)

            {

                if (!Object.Equals(value, other))

                    return null;

            }

            else

            {

                // check that both objects are IComparables

                if (!(value is IComparable) || !(other is IComparable))

                    return new ValidationResult(String.Format("{0} and {1} must both implement IComparable", validationContext.DisplayName, OtherProperty));



                // compare the objects

                var result = Comparer.Default.Compare(value, other);



                switch (Criteria)

                {

                    case CompareValues.GreaterThan:

                        if (result > 0)

                            return null;

                        break;

                    case CompareValues.LessThan:

                        if (result < 0)

                            return null;

                        break;

                    case CompareValues.GreatThanOrEqualTo:

                        if (result >= 0)

                            return null;

                        break;

                    case CompareValues.LessThanOrEqualTo:

                        if (result <= 0)

                            return null;

                        break;

                }

            }



            // got this far must mean the items don't meet the comparison criteria

            return new ValidationResult(ErrorMessage);

        }

    }



    /// <summary>

    /// Indicates a comparison criteria used by the CompareValues attribute

    /// </summary>

    public enum CompareValues

    {

        EqualTo,

        NotEqualTo,

        GreaterThan,

        LessThan,

        GreatThanOrEqualTo,

        LessThanOrEqualTo

    }

 

应用的时候直接在指定的属性上添加此CompareValuesAttribute标签即可

【注：第一个参数是要与之比较的属性名，第二个参数表示两个属性值之间的大小关系，第三个参数表示错误提示信息】

public class EricSunModel

{

    [Display(Name = "Ready Time")]

    public string ReadyTime { get; set; }



    [CompareValues("ReadyTime", CompareValues.GreaterThan, ErrorMessage = "Close time must be later than ready time")]

    [Display(Name = "Close Time")]

    public string CloseTime { get; set; }



}

 

 

更多细节可以参考如下链接：

http://cncrrnt.com/blog/index.php/2011/01/custom-validationattribute-for-comparing-properties/ 

 

 

分类:  Asp.Net MVC