数据注释 - 如何使用MVC3中的Web.Config值替换Range值？

Question

如何用MVC3中的Web.Config值替换Range值？

[Range(5, 20, ErrorMessage = "Initial Deposit should be between $5.00 and $20.00")
public decimal InitialDeposit { get; set; }

web.config中:

<add key="MinBalance" value="5.00"/>
<add key="MaxDeposit" value="20.00"/>

Answer 1

您需要创建继承RangeAttribute和实现的自定义属性IClientValidatable.

    public class ConfigRangeAttribute : RangeAttribute, IClientValidatable
    {
        public ConfigRangeAttribute(int Int) :
            base
            (Convert.ToInt32(WebConfigurationManager.AppSettings["IntMin"]),
             Convert.ToInt32(WebConfigurationManager.AppSettings["IntMax"])) { }

        public ConfigRangeAttribute(double Double) :
            base
            (Convert.ToDouble(WebConfigurationManager.AppSettings["DoubleMin"]),
             Convert.ToDouble(WebConfigurationManager.AppSettings["DoubleMax"])) 
        {
            _double = true;
        }

        private bool _double = false;

        public override string FormatErrorMessage(string name)
        {
            return String.Format(ErrorMessageString, name, this.Minimum, this.Maximum);
        }

        public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
        {
            var rule = new ModelClientValidationRule
            {
                ErrorMessage = FormatErrorMessage(this.ErrorMessage),
                ValidationType = "range",
            };
            rule.ValidationParameters.Add("min", this.Minimum);
            rule.ValidationParameters.Add("max", this.Maximum);
            yield return rule;
        }

        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            if (value == null)
                return null;

            if (String.IsNullOrEmpty(value.ToString()))
                return null;

            if (_double)
            {
                var val = Convert.ToDouble(value);
                if (val >= Convert.ToDouble(this.Minimum) && val <= Convert.ToDouble(this.Maximum))
                    return null;
            }
            else
            {
                var val = Convert.ToInt32(value);
                if (val >= Convert.ToInt32(this.Minimum) && val <= Convert.ToInt32(this.Maximum))
                    return null;
            }

            return new ValidationResult(
                FormatErrorMessage(this.ErrorMessage)
            );
        }
    }

用法示例:

[ConfigRange(1)]
public int MyInt { get; set; }

[ConfigRange(1.1, ErrorMessage = "This one has gotta be between {1} and {2}!")]
public double MyDouble { get; set; }

第一个示例将返回默认错误消息,第二个示例将返回您的自定义错误消息.两者都将使用web.config中定义的范围值.