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我正在使用 Value Injector 来管理我在 ASP.NET MVC 项目中的映射，到目前为止效果很好。域具有长度测量的概念，作为标准度量单位存储在数据库中，并作为十进制值公开给服务层。

在 UI 上下文中渲染长度，具体取决于被测量的对象、用户文化等。有关上下文的提示由视图模型类型的属性上的属性表示。使用值注入器，我想在注入时检查这些属性并显示一个适当格式的字符串来显示，当源属性是小数并且目标属性是用上述属性之一装饰的字符串时。

namespace TargetValueAttributes
{
    public class Person
    {
        public decimal Height { get; set; }
        public decimal Waist { get; set; }
    }

    public class PersonViewModel
    {
        [LengthLocalizationHint(LengthType.ImperialFeetAndInches)]
        [LengthLocalizationHint(LengthType.MetricMeters)]
        public string Height { get; set; }

        [LengthLocalizationHint(LengthType.ImperialInches)]
        [LengthLocalizationHint(LengthType.MetricCentimeters)]
        public string Waist { get; set; }
    }

    public enum LengthType
    {
        MetricMeters,
        MetricCentimeters,
        ImperialFeetAndInches,
        ImperialInches
    }

    [AttributeUsage(AttributeTargets.Property, AllowMultiple = true)]
    public class LengthLocalizationHintAttribute : Attribute
    {
        public LengthType SuggestedLengthType { get; set; }

        public LengthLocalizationHintAttribute(LengthType suggestedLengthType)
        {
            SuggestedLengthType = suggestedLengthType;
        }
    }

    public class LengthLocalizationInjection : FlatLoopValueInjection<decimal, string>
    {
        protected override void Inject(object source, object target)
        {
            base.Inject(source, target);//I want to be able to inspect the attributes on the target value here
        }
        protected override string SetValue(decimal sourceValues)
        {
            var derivedLengthType = LengthType.MetricMeters;//here would be even better
            return sourceValues.ToLength(derivedLengthType);//this is an extension method that does the conversion to whatever the user needs to see
        }
    }
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1 回答 1

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在源代码中四处寻找之后，我提出了一个基于“FlatLoopValueInjection”实现的解决方案。

public abstract class LocalizationStringInjection<TSource, TTarget> : LoopValueInjectionBase
{
    public ILocalizationContext LocalizationContext { get; set; }

    protected LocalizationStringInjection(ILocalizationContext localizationContext)
    {
        LocalizationContext = localizationContext;
    }

    protected virtual bool TypesMatch(Type sourceType, Type targetType)
    {
        return sourceType == typeof(TSource) && targetType == typeof(TTarget);
    }

    protected override void Inject(object source, object target)
    {
        foreach (PropertyDescriptor targetPropertyDescriptor in target.GetProps())
        {
            var t1 = targetPropertyDescriptor;
            var es = UberFlatter.Flat(targetPropertyDescriptor.Name, source, type => TypesMatch(type, t1.PropertyType));

            var endpoint = es.FirstOrDefault();
            if (endpoint == null) continue;

            var sourceValue = endpoint.Property.GetValue(endpoint.Component) is TSource ? (TSource)endpoint.Property.GetValue(endpoint.Component) : default(TSource);

            if (AllowSetValue(sourceValue))
                targetPropertyDescriptor.SetValue(target, SetValue(sourceValue, targetPropertyDescriptor));
        }
    }

    protected abstract TTarget SetValue(TSource sourcePropertyValue, PropertyDescriptor targetPropertyDescriptor);
}

public class LengthLocalizationStringInjection : LocalizationStringInjection<decimal, string>
{
    public LengthLocalizationStringInjection(ILocalizationContext localizationContext) : base(localizationContext) { }

    protected override string SetValue(decimal sourceValue, PropertyDescriptor targetPropertyDescriptor)
    {
        var lengthHints = targetPropertyDescriptor.Attributes.Cast<object>().Where(attribute => attribute.GetType() == typeof(LengthLocalizationAttribute)).Cast<LengthLocalizationAttribute>().ToList();
        return lengthHints.Any() ? sourceValue.ToLength(lengthHints.First(l => l.SuggestedLengthType == LocalizationContext.Length).SuggestedLengthType) : sourceValue.ToLength(default(LengthType));
    }
}

事实证明，这对于我现在的目的来说已经足够好了。我省略了一些引用类型，以免混淆这个想法。

于 2012-03-26T19:40:20.670 回答