通过发送XmlEnumAttribute c＃获取枚举的元素？ [英] Get element of an enum by sending XmlEnumAttribute c#?
问题描述
我通常不必问问题，因为大多数时候我都可以在互联网上找到所需的东西，但是现在我还没有找到一种方法来解决这个问题：
I normaly dont have to ask questions because most of the times I find what I need on internet, but now i haven´t find a way to get this:
想象一下，我喜欢这个枚举中的50000个枚举元素：
Imagine that I have like 50000 enum elements in this enum:
public enum myEnum
{
[System.Xml.Serialization.XmlEnumAttribute("01010101")]
Item01010101,
[System.Xml.Serialization.XmlEnumAttribute("10101500")]
Item10101500
}
我想要做的是通过传递元素的XmlEnumAttribute的字符串值来获得元素值，例如
what i am trying to do is to get the element value by passing the string value for XmlEnumAttribute of the element, for example
object.ItsEnumValue = getEnumElement("01010101");
// Function which will return the element of the enum.
public myEnum getEnumElement(string xmlAttributeValue)
{
// The function should return the enum element, not using a switch statement
return myEnum.Item01010101;
}
没有switch语句，有没有办法做到这一点？
我希望您能帮助我，谢谢。
Is there a way to do this without a switch statement? I hope you can help me, thanks.
推荐答案
您有几种方法可以解决此问题。
You have a couple methods to solve this problem.
首先，您可以使用反射通过 typeof（TEnum）.GetFields（BindingFlags.Public | BindingFlags.Static）遍历所有枚举值
Firstly, you can use reflection to cycle through all the enum values using typeof(TEnum).GetFields(BindingFlags.Public | BindingFlags.Static) similarly to how it is done in this this answer:
public static partial class XmlEnumExtensions
{
public static TEnum FromReflectedXmlValue<TEnum>(this string xml) where TEnum : struct, IConvertible, IFormattable
{
// Adapted from https://stackoverflow.com/questions/35294530/c-sharp-getting-all-enums-value-by-attribute
var obj = (from field in typeof(TEnum).GetFields(BindingFlags.Public | BindingFlags.Static)
from attr in field.GetCustomAttributes<XmlEnumAttribute>()
where attr != null && attr.Name == xml
select field.GetValue(null)).SingleOrDefault();
if (obj != null)
return (TEnum)obj;
// OK, maybe there is no XmlEnumAttribute override so match on the name.
return (TEnum)Enum.Parse(typeof(TEnum), xml, false);
}
}
然后使用它：
obj.ItsEnumValue = "01010101".FromReflectedXmlValue<myEnum>();
但是，当 [Flags] 属性已应用。例如，给定以下枚举：
However, this will not work when the [Flags] attribute is applied. For instance, given the following enum:
[Flags]
public enum myFlagsEnum
{
[System.Xml.Serialization.XmlEnumAttribute("Flag0")]
Zero = (1 << 0),
[System.Xml.Serialization.XmlEnumAttribute("Flag1")]
One = (1 << 1),
}
从值 myFlagsEnum.Zero | myFlagsEnum.One ， XmlSerializer 将生成以下组合字符串，不能仅通过反射找到： Flag0 Flag1 。将多个 XmlEnumAttribute 属性应用于给定的枚举值，或者仅某些枚举值具有 XmlEnumAttribute
From the value myFlagsEnum.Zero | myFlagsEnum.One, XmlSerializer will generate the following combined string, which cannot be found purely by reflection: Flag0 Flag1. Nor is it clear what should happen when multiple XmlEnumAttribute attributes are applied to a given enum value, or only some of the enum values have XmlEnumAttribute applied.
要处理包括上述内容在内的所有可能的边缘情况，我建议直接使用以下方法直接对XML进行反序列化第二种方法：
To handle all possible edge cases including the above, I would suggest simply deserializing the XML directly, using the following second method:
public static partial class XmlExtensions
{
static XmlExtensions()
{
noStandardNamespaces = new XmlSerializerNamespaces();
noStandardNamespaces.Add("", ""); // Disable the xmlns:xsi and xmlns:xsd attributes.
}
readonly static XmlSerializerNamespaces noStandardNamespaces;
internal const string RootNamespace = "XmlExtensions";
internal const string RootName = "Root";
public static TEnum FromXmlValue<TEnum>(this string xml) where TEnum : struct, IConvertible, IFormattable
{
var element = new XElement(XName.Get(RootName, RootNamespace), xml);
return element.Deserialize<XmlExtensionsEnumWrapper<TEnum>>().Value;
}
public static T Deserialize<T>(this XContainer element, XmlSerializer serializer = null)
{
using (var reader = element.CreateReader())
{
object result = (serializer ?? new XmlSerializer(typeof(T))).Deserialize(reader);
if (result is T)
return (T)result;
}
return default(T);
}
public static string ToXmlValue<TEnum>(this TEnum value) where TEnum : struct, IConvertible, IFormattable
{
var root = new XmlExtensionsEnumWrapper<TEnum> { Value = value };
return root.SerializeToXElement().Value;
}
public static XElement SerializeToXElement<T>(this T obj)
{
return obj.SerializeToXElement(null, noStandardNamespaces); // Disable the xmlns:xsi and xmlns:xsd attributes by default.
}
public static XElement SerializeToXElement<T>(this T obj, XmlSerializer serializer, XmlSerializerNamespaces ns)
{
var doc = new XDocument();
using (var writer = doc.CreateWriter())
(serializer ?? new XmlSerializer(obj.GetType())).Serialize(writer, obj, ns);
var element = doc.Root;
if (element != null)
element.Remove();
return element;
}
}
[XmlRoot(XmlExtensions.RootName, Namespace = XmlExtensions.RootNamespace)]
[XmlType(IncludeInSchema = false)]
public class XmlExtensionsEnumWrapper<TEnum>
{
[XmlText]
public TEnum Value { get; set; }
}
这样可以保证与 XmlSerializer 在所有情况下-实际使用它。然后类似地执行以下操作：
This guarantees compatibility with XmlSerializer in all cases - by actually using it. Then similarly do:
obj.ItsEnumValue = "01010101".FromXmlValue<myEnum>();
示例小提琴。
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