ASP.Net MVC探索之路 - Model的比较验证

WebForm有一个比较验证服务器控件CompareValidator ，可以比较两个控件的值大小或一个控件与某一个具体值的大小。可以进行string,int,double,DateTime,decimal这些数据类型的==、!=、>、<、>=、<=比较。在ASP.NET MVC 2.0中，我们已经可以使用基于DataAnnotations的校验方式，对Model的值进行空校验(Required)、范围校验(Range)、字符串长度校验(StringLengthAttribute)等。在ASP.NET MVC 3中，我们还可以使用CompareAttribute进行简单的相等(==)校验，但仅此而已，其他校验就没有了。

这里我们定义一个类似WebForms验证服务器控件CompareValidator的Attribule。

首先定义一个枚举表示我们要比较的数据类型：

    public enum ValidationDataType : byte
    {
        String,Integer,Double,Date,Currency/*Decimal*/
    }

再定义一个枚举表示比较方式：

    public enum ValidationCompareOperator : byte
    {
        Equal, NotEqual,GreaterThan,GreaterThanEqual,LessThan,LessThanEqual
    }

然后当然就是主角CompareAttribute:

    [AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = true)]
    public class CompareAttribute : ValidationAttribute
    {
        public string SourceProperty { get; private set; }
        public string OriginalProperty { get; private set; }
        public ValidationCompareOperator Operator { get; private set; }
        public ValidationDataType Type{ get; private set; }

        private const string _defaultErrorMessage = "'{0}' 与 '{1}' 进行 {2} 比较失败";

        public CompareAttribute(string sourceProperty, string originalProperty
, ValidationCompareOperator op, ValidationDataType type)
            : base(_defaultErrorMessage)
        {
            SourceProperty = sourceProperty;
            OriginalProperty = originalProperty;
            Operator = op;
            Type = type;
        }

        public override string FormatErrorMessage(string name)
        {
            return String.Format(CultureInfo.CurrentUICulture, ErrorMessageString,
                SourceProperty, OriginalProperty, Operator.ToString());
        }

        public override bool IsValid(object value)
        {
            PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(value);
            object sourceProperty = properties.Find(SourceProperty, true /* ignoreCase */)
.GetValue(value);
            object originalProperty = properties.Find(OriginalProperty, true /* ignoreCase */)
.GetValue(value);

            return compare(sourceProperty,originalProperty);
        }

        private bool compare(object sourceProperty, object originalProperty)
        {
            int num = 0;
            switch (this.Type)
            { 
                case ValidationDataType.String:
                    num = string.Compare((string)sourceProperty
, (string)originalProperty, false, CultureInfo.CurrentCulture);
                    break;

                case ValidationDataType.Integer:
                    num = ((int)sourceProperty).CompareTo(originalProperty);
                    break;

                case ValidationDataType.Double:
                    num = ((double)sourceProperty).CompareTo(originalProperty);
                    break;

                case ValidationDataType.Date:
                    num = ((DateTime)sourceProperty).CompareTo(originalProperty);
                    break;

                case ValidationDataType.Currency:
                    num = ((decimal)sourceProperty).CompareTo(originalProperty);
                    break;
            }
            switch (this.Operator)
            {
                case ValidationCompareOperator.Equal:
                    return (num == 0);

                case ValidationCompareOperator.NotEqual:
                    return (num != 0);

                case ValidationCompareOperator.GreaterThan:
                    return (num > 0);

                case ValidationCompareOperator.GreaterThanEqual:
                    return (num >= 0);

                case ValidationCompareOperator.LessThan:
                    return (num < 0);

                case ValidationCompareOperator.LessThanEqual:
                    return (num <= 0);
            }
            return true;

        }
    }

在Model中就可以这样使用了，以下校验两次输入的密码是否一致：

    [Compare("PasswordConfirm", "Password", ValidationCompareOperator.Equal
,ValidationDataType.String, ErrorMessage = "请确认两次输入的密码一致")]
    public class UserInputEdit
    {
        [DisplayName("登录密码")]
        public string Password { get; set; }

        [DisplayName("确认密码")]
        public string PasswordConfirm { get; set; }
    }

如果果要Model中有两个时间，开始时间和结束时间，要求结束时间必须大于开始时间：

    [Compare("TimeEnd", "TimeStart", ValidationCompareOperator.GreaterThan
, ValidationDataType.Date, ErrorMessage = "结束时间必须大于开始时间")]
    public class UserInputEdit
    {
        [DisplayName("开始时间")]
        public DateTime TimeStart { get; set; }

        [DisplayName("结束时间")]
        public DateTime TimeEnd { get; set; }
    }

ASP.NET MVC 3也有一个CompareAttribute，但它只能进行Equals比较。同样的比较两次密码是否一致，以上代码可以写成这样：

    public class UserInputEdit
    {
        [DisplayName("登录密码")]
        public string Password { get; set; }

        [DisplayName("确认密码")]
        [Compare("Password", ErrorMessage = "请确认两次输入的密码一致")]
        public string PasswordConfirm { get; set; }
    }

在我们自定义的CompareAttribute中，必须将Attribute应用于class上。如果您想像ASP.NET MVC 3中，将标记写在属性，很遗憾不行。因为ValidationResult IsValid(...)的方法在.Net 4才有，MVC 3也才有相应的支持。如果您已经在使用.Net 4,也可以像下面一样修改我们自定义的CompareAttribute，但请注意以下代码我没测试过：

    [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field
, AllowMultiple = true)]
    public class CompareAttribute : ValidationAttribute
    {
        public string OriginalProperty { get; private set; }
        public ValidationCompareOperator Operator { get; private set; }
        public ValidationDataType Type{ get; private set; }

        private const string _defaultErrorMessage = "'{0}' 与 '{1}' 进行 {2} 比较失败";

        public CompareAttribute(string originalProperty
, ValidationCompareOperator op, ValidationDataType type)
            : base(_defaultErrorMessage)
        {
            OriginalProperty = originalProperty;
            Operator = op;
            Type = type;
        }

        public override string FormatErrorMessage(string name)
        {
            return String.Format(CultureInfo.CurrentUICulture, ErrorMessageString,
                name, OriginalProperty, Operator.ToString());
        }

        protected override ValidationResult IsValid(object value
, ValidationContext validationContext)
        {
            PropertyInfo originalProperty = validationContext.ObjectType
.GetProperty(this.OriginalProperty);
            object originalValue = originalProperty.GetValue(validationContext.ObjectInstance, null);

            if(!compare(value, originalValue))
                return new ValidationResult(this.FormatErrorMessage(validationContext
.DisplayName));

            return null;
        }

        private bool compare(object sourceProperty, object originalProperty)
        {
            int num = 0;
            switch (this.Type)
            { 
                case ValidationDataType.String:
                    num = string.Compare((string)sourceProperty
, (string)originalProperty, false, CultureInfo.CurrentCulture);
                    break;

                case ValidationDataType.Integer:
                    num = ((int)sourceProperty).CompareTo(originalProperty);
                    break;

                case ValidationDataType.Double:
                    num = ((double)sourceProperty).CompareTo(originalProperty);
                    break;

                case ValidationDataType.Date:
                    num = ((DateTime)sourceProperty).CompareTo(originalProperty);
                    break;

                case ValidationDataType.Currency:
                    num = ((decimal)sourceProperty).CompareTo(originalProperty);
                    break;
            }
            switch (this.Operator)
            {
                case ValidationCompareOperator.Equal:
                    return (num == 0);

                case ValidationCompareOperator.NotEqual:
                    return (num != 0);

                case ValidationCompareOperator.GreaterThan:
                    return (num > 0);

                case ValidationCompareOperator.GreaterThanEqual:
                    return (num >= 0);

                case ValidationCompareOperator.LessThan:
                    return (num < 0);

                case ValidationCompareOperator.LessThanEqual:
                    return (num <= 0);
            }
            return true;

        }
    }