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Adnotare enum cu mai multe valori

Cand dorim sa serializam un enum putem sa atasam la valoarea fiecarui item din enum atributul XmlEnumAttribute. Astfel la serializare/deserializare o sa putem lucra cu o valoarea string nu cu o valoare numerica.
Pana aici nici o problema, dar cum facem sa obtinem doar aceasta valoarea si nu un xml care contine si aceasta valoarea . De exemplu pentru enum-ul:
public enum Dimension
{
[XmlEnum(Name="BigT")]
Big
[XmlEnum(Name="SmallT")]
Small
}

am obține folosindu-ne de XmlSerializer un output care contine si un nod care specifica ce tip de data ii. Pentru a putea sa obtinem doar valoare BigT sau SmallT putem sa apelam la reflection si sa iteram prin atributele item-ului respectiv pana ajungem la un atribut de tip XmlEnumAttribute.
Acuma, daca ducem problema umpic mai departe, putem sa ajungem la cazuri in care elementele din enum au diferite valori. De exemplu daca lucram cu doua sau mai multe aplicații, putem sa avem doua sau mai multe reprezentări pentru aceiasi valoare. De exemplu o aplicație poate sa isi noteze valoare Big cu BigT, iar alta cu BigState. La prima strigare putem sa scriem un swith, iar in funcție de sistemul de unde preluam sau trimitem date sa avem o anumita valoare.
O solutie mai generala este sa scriem doua metode care sa stie sa convertească un string intr-un enum in functie de valoarea atributelor cu care adnotam un anumit item din enum. De exemplu in exemplul dat mai sus putem sa avem:
public enum Dimension
{
[FirstSystem("BigT")]
[SecondSystem("BigState")]
Big
[FirstSystem(Name="SmallT")]
[SecondSystem("SmallState")]
Small
}
In felul acesta, putem sa avem oricate valori pentru un anum. Atributele custom pe care le-am definit trebuie sa mosteneasca din clasa XmlEnumAttribute. Se poate scrie si un atribut custom, dar am folosit aceasta clasa deoarece deja continea o valoare de tip string.
Mai jos gasiti doua metode care ne permit sa convertim un enum in string si viceversa pe baza atributelor. Pentru a putea obtine valorea unui atribut este nevoie sa iteram prin toata lista de atribute pana ajungem la atributul pe care noi il dorim.
 public static string GetAttributeValue<TAttribute>(Enum @enum)
where TAttribute: XmlEnumAttribute
{
Type enumType = @enum.GetType();
Type attributeType = typeof (TAttribute);
FieldInfo info = enumType.GetField(@enum.ToString("G"));
if (!info.IsDefined(typeof(XmlEnumAttribute), false))
{
return @enum.ToString("G");
}

foreach (var customAttribute in info.GetCustomAttributes(attributeType, false))
{
if (customAttribute.GetType() == attributeType)
{
XmlEnumAttribute attribute = (XmlEnumAttribute)customAttribute;
return attribute.Name;
}
}

throw new Exception("The given attribute could not be found.");
}


public static TEnum GetEnumByAttributeValue<TEnum,TAttribute>(string value)
where TAttribute: XmlEnumAttribute
{
Type enumType = typeof(TEnum);

foreach (var item in Enum.GetValues(enumType))
{
if(GetAttributeValue<TAttribute>((Enum)item)==value)
{
return (TEnum)Enum.Parse(enumType, item.ToString());
}
}

throw new IndexOutOfRangeException(string.Format("The {0} attribute value cannot be found on the {1} enum", value, enumType.Name));
}

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