在Asp.Net MVC中实现CompareValues标签对Model中的属性进行验证
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：
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/// <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
}
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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】
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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; }