c# - 如何高效地使用 GetProperties()？

Question

public object GetObjectToSerialize(object value, Type targetType)
{
      var allProperties = value.GetType().GetProperties();

      var passwordProperties = allProperties.Where(p => p.PropertyType == typeof(string))
                                            .Where(p => p.Name.Contains("Password"))
                                            .ToList();

      var passwordWithoutEncryptedAttribute = passwordProperties
                .Where(p => !p.GetCustomAttributes(typeof(EncryptedConfigurationItemAttribute), false).Any());

       if (passwordWithoutEncryptedAttribute.Any())
       {
            throw new InvalidOperationException(SafeFormatter.Format(BackgroundJobsLocalization.Culture, BackgroundJobsLocalization.PasswordWithoutEncryptedAttribute));
       }

       foreach (var property in passwordProperties)
       {
            property.SetValue(value, null, null);
       }

        return value;
 }

我经常使用这种方法。我该如何优化它？因为据我所知，value.GetType().GetProperties(); 递归工作(对于基础对象，然后对于基础对象属性，然后是基础对象属性的每个属性，等等)

Answer 1

通过 memoizing它的结果。将结果保存在 Dictionary<Type, PropertyInfo[]> 中，然后在函数的开头检查您是否已经计算过它。如果是，返回 Dictionary<,> 的值.如果你想让它线程安全，使用 ConcurrentDictionary<Type, PropertyInfo[]> .

类似于:

//private static readonly Dictionary<Type, PropertyInfo[]> PasswordProperties = new Dictionary<Type, PropertyInfo[]>();
private static readonly ConcurrentDictionary<Type, PropertyInfo[]> PasswordProperties = new ConcurrentDictionary<Type, PropertyInfo[]>();

public static object GetObjectToSerialize(object value, Type targetType) {
    Type type = value.GetType();

    PropertyInfo[] properties;

    if (!PasswordProperties.TryGetValue(type, out properties)) 
    {
        properties = type.GetProperties()
                         .Where(p => p.PropertyType == typeof(string))
                         .Where(p => p.Name.Contains("Password"))
                         .ToArray();

        var passwordWithoutEncryptedAttribute = properties
                    .Where(p => !p.GetCustomAttributes(typeof(EncryptedConfigurationItemAttribute), false).Any());

        if (passwordWithoutEncryptedAttribute.Any()) {
            throw new InvalidOperationException(); // SafeFormatter.Format(BackgroundJobsLocalization.Culture, BackgroundJobsLocalization.PasswordWithoutEncryptedAttribute));
        }

        PasswordProperties[type] = properties;
    }

    foreach (var property in properties) 
    {
        property.SetValue(value, null, null);
    }

    return value;
}

如果您有权访问 value 的类型在编译时，它可以通过另一种方式进行优化，通过在静态泛型类的字段中进行内存:

public static class ObjectHelper
{
    public static T GetObjectToSerialize<T>(T value) 
    {
        foreach (var property in ObjectHelperInner<T>.Properties) 
        {
            property.SetValue(value, null, null);
        }

        return value;
    }

    private static class ObjectHelperInner<T>
    {
        public static readonly PropertyInfo[] Properties;

        static ObjectHelperInner()
        {
            PropertyInfo[] properties = typeof(T).GetProperties()
                                                    .Where(p => p.PropertyType == typeof(string))
                                                    .Where(p => p.Name.Contains("Password"))
                                                    .ToArray();

            var passwordWithoutEncryptedAttribute = properties
                        .Where(p => !p.GetCustomAttributes(typeof(EncryptedConfigurationItemAttribute), false).Any());

            if (passwordWithoutEncryptedAttribute.Any()) {
                throw new InvalidOperationException(); // SafeFormatter.Format(BackgroundJobsLocalization.Culture, BackgroundJobsLocalization.PasswordWithoutEncryptedAttribute));
            }

            Properties = properties;
        }
    }
}

代码的第二个版本不会工作，如果你有:

object obj = something;
ObjectHelper.GetObjectToSerialize(obj);

它只有在你有以下条件时才有效:

SomeConcreteType obj = something;
ObjectHelper.GetObjectToSerialize(obj);

另一种可能的解决方案是在运行时生成(通过 Expression 树)一些代码来清理对象。它变得更快，但代码生成变得更慢。而且执行此操作的代码要复杂得多。