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我在玩企業庫驗證塊。我有一個來自我在MVC項目中使用的Linq To Entities edmx文件的類。我想確保Nullable DateTime總是晚於DateTime。我在元數據類中使用屬性來創建默認規則集。當嘗試使用PropertyComparisonValidator進行驗證時，我得到以下異常：可用於空值的企業庫驗證塊<DateTime>
PropertyComparisonValidatorAttribute類型的驗證屬性不能用於驗證值。
我推理說我無法將Nullable類型與結構進行比較，所以我編寫了下面的自定義類來避開感知問題。我仍然得到以下例外：
NullableDateComparisonValidatorAttribute類型的驗證屬性不能用於驗證值。
接下來，我嘗試從企業庫中進行自我驗證，驗證失敗後失敗。直到我明白這一點，我才處於暫時停滯狀態。請建議一個不太難看的解決方案\解決方法。
using System;
using System.Reflection;
using Microsoft.Practices.EnterpriseLibrary.Validation;
using Microsoft.Practices.EnterpriseLibrary.Validation.Validators;
namespace IdahoUtility
{
public class NullableComparisonValidator<T> : Validator<Nullable<T>>
where T: struct, IComparable
{
protected string propertyToCompare { get; set; }
protected ComparisonOperator comparisionOperator { get; set; }
protected T TargetProperty(object currentTarget)
{
if (null == currentTarget)
{
throw new ArgumentNullException("currentTarget");
}
Type t = currentTarget.GetType();
PropertyInfo pInfo = t.GetProperty(propertyToCompare);
object oValue = pInfo.GetValue(currentTarget, null);
if (oValue.GetType() != typeof(T))
{
throw new InvalidOperationException(string.Format("Property compared must be a {0}!",typeof(T)));
}
return (T)oValue;
}
public NullableComparisonValidator(string PropertyToCompare, ComparisonOperator cmpOp)
:base(null,null)
{
if (string.IsNullOrWhiteSpace(PropertyToCompare))
{
throw new ArgumentException("PropertyToCompare is Invalid!", "PropertyToCompare");
}
propertyToCompare = PropertyToCompare;
comparisionOperator = cmpOp;
}
protected override void DoValidate(Nullable<T> objectToValidate, object currentTarget, string key, ValidationResults validationResults)
{
// ignore nulls
if (null == objectToValidate)
{
return;
}
switch (comparisionOperator)
{
case ComparisonOperator.Equal:
DoValidateEqual(objectToValidate, currentTarget, key, validationResults);
break;
case ComparisonOperator.GreaterThan:
DoValidateGreaterThan(objectToValidate, currentTarget, key, validationResults);
break;
case ComparisonOperator.GreaterThanEqual:
DoValidateGreaterThanEqual(objectToValidate, currentTarget, key, validationResults);
break;
case ComparisonOperator.LessThan:
DoValidateLessThan(objectToValidate, currentTarget, key, validationResults);
break;
case ComparisonOperator.LessThanEqual:
DoValidateLessThanEqual(objectToValidate, currentTarget, key, validationResults);
break;
case ComparisonOperator.NotEqual:
DoValidateNotEqual(objectToValidate, currentTarget, key, validationResults);
break;
}
}
private void DoValidateLessThanEqual(Nullable<T> objectToValidate, object currentTarget, string key, ValidationResults validationResults)
{
if (objectToValidate.Value.CompareTo(TargetProperty(currentTarget)) > 0)
{
LogValidationResult(validationResults, string.Format("Should be less than or equal to {0}!", propertyToCompare), currentTarget, key);
}
}
private void DoValidateLessThan(Nullable<T> objectToValidate, object currentTarget, string key, ValidationResults validationResults)
{
if (objectToValidate.Value.CompareTo(TargetProperty(currentTarget)) >= 0)
{
LogValidationResult(validationResults, string.Format("Should be less than {0}!", propertyToCompare), currentTarget, key);
}
}
private void DoValidateGreaterThanEqual(Nullable<T> objectToValidate, object currentTarget, string key, ValidationResults validationResults)
{
if (objectToValidate.Value.CompareTo(TargetProperty(currentTarget)) < 0)
{
LogValidationResult(validationResults, string.Format("Should be greater than or equal {0}!", propertyToCompare), currentTarget, key);
}
}
private void DoValidateGreaterThan(Nullable<T> objectToValidate, object currentTarget, string key, ValidationResults validationResults)
{
if (objectToValidate.Value.CompareTo(TargetProperty(currentTarget)) <= 0)
{
LogValidationResult(validationResults, string.Format("Should be greater than {0}!", propertyToCompare), currentTarget, key);
}
}
private void DoValidateEqual(Nullable<T> objectToValidate, object currentTarget, string key, ValidationResults validationResults)
{
if (objectToValidate.Value.CompareTo(TargetProperty(currentTarget)) != 0)
{
LogValidationResult(validationResults, string.Format("Should be equal to {0}!", propertyToCompare), currentTarget, key);
}
}
private void DoValidateNotEqual(Nullable<T> objectToValidate, object currentTarget, string key, ValidationResults validationResults)
{
if (objectToValidate.Value.CompareTo(TargetProperty(currentTarget)) == 0)
{
LogValidationResult(validationResults, string.Format("Should not be equal to {0}!", propertyToCompare), currentTarget, key);
}
}
protected override string DefaultMessageTemplate
{
get { return "{0}"; }
}
}
}