/// <summary>
/// Validates the specified value with respect to the current validation attribute.
/// </summary>
/// <param name="value"></param>
/// <param name="validationContext"></param>
/// <returns></returns>
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
if (value == null)
{
return(null);
}
object entity = validationContext.ObjectInstance;
Type type = validationContext.ObjectType;
while (type.GetTypeInfo().Assembly.IsDynamic)
{
type = type.GetTypeInfo().BaseType;
}
var databaseContext = validationContext.GetRequiredService <IDatabaseContext>();
var entityContext = databaseContext.GetDynamicContext(type);
if (value is string && !IsCaseSensitive)
{
value = ((string)value).ToLower();
}
ParameterExpression parameter = Expression.Parameter(type);
IEntityMetadata metadata = EntityDescriptor.GetMetadata(type);
Expression left = Expression.NotEqual(Expression.Property(parameter, metadata.KeyProperty.ClrName), Expression.Constant(metadata.KeyProperty.GetValue(entity)));
Expression right;
if (value is string && IsCaseSensitive)
{
right = Expression.Equal(Expression.Property(parameter, validationContext.MemberName), Expression.Constant(value));
}
else
{
right = Expression.Equal(Expression.Call(Expression.Property(parameter, validationContext.MemberName), typeof(string).GetMethod("ToLower")), Expression.Constant(value));
}
Expression expression = Expression.And(left, right);
expression = Expression.Lambda(typeof(Func <,>).MakeGenericType(type, typeof(bool)), expression, parameter);
dynamic where = _QWhereMethod.MakeGenericMethod(type).Invoke(null, new[] { entityContext.Query(), expression });
int count = ((Task <int>)entityContext.CountAsync(where)).Result;;
if (count != 0)
{
if (ErrorMessage != null)
{
return(new ValidationResult(ErrorMessage));
}
else
{
return(new ValidationResult(string.Format("{0}不能为“{1}”，因为数据库已存在同样的值。", validationContext.DisplayName, value)));
}
}
else
{
return(ValidationResult.Success);
}
}
