Retrieve enum value based on XmlEnumAttribute name value

Question

I need a Generic function to retrieve the name or value of an enum based on the XmlEnumAttribute "Name" property of the enum. For example I have the following enum defined:

Public Enum Currency
   <XmlEnum("00")> CDN = 1
   <XmlEnum("01")> USA= 2
   <XmlEnum("02")> EUR= 3
   <XmlEnum("03")> JPN= 4
End Enum

The first Currency enum value is 1; the enum name is "CDN"; and the XMLEnumAttribute Name property value is "00".

If I have the enum value, I can retrieve the XmlEnumAttribute "Name" value using the following generic function:

Public Function GetXmlAttrNameFromEnumValue(Of T)(ByVal pEnumVal As T) As String

        Dim type As Type = pEnumVal.GetType
        Dim info As FieldInfo = type.GetField([Enum].GetName(GetType(T), pEnumVal))
        Dim att As XmlEnumAttribute = CType(info.GetCustomAttributes(GetType(XmlEnumAttribute), False)(0), XmlEnumAttribute) 'If there is an xmlattribute defined, return the name

        Return att.Name
    End Function

So using the above function, I can specify the Currency enum type, pass a value of 1, and the return value will be "00".

What I need is a function to perform if the opposite. If I have the XmlEnumAttribute Name value "00", I need a function to return a Currency enum with a value of 1. Just as useful would be a function that would return the enum name "CDN". I could then simply parse this to get the enum value.

Any assistance would be appreciated.

Answer 1

A requirement to solve this exact same problem led me to this question and answer. As I develop in VB.NET, I rewrote CkH's solution into VB and modified it to use your GetXmlAttrNameFromEnumValue function.

Public Shared Function GetCode(Of T)(ByVal value As String) As T
    For Each o As Object In System.Enum.GetValues(GetType(T))
        Dim enumValue As T = CType(o, T)
        If GetXmlAttrNameFromEnumValue(Of T)(enumValue).Equals(value, StringComparison.OrdinalIgnoreCase) Then
            Return CType(o, T)
        End If
    Next

    Throw New ArgumentException("No code exists for type " + GetType(T).ToString() + " corresponding to value of " + value)
End Function

C# Version:

public static string GetXmlAttrNameFromEnumValue<T>(T pEnumVal)
{
    // http://stackoverflow.com/q/3047125/194717
    Type type = pEnumVal.GetType();
    FieldInfo info = type.GetField(Enum.GetName(typeof(T), pEnumVal));
    XmlEnumAttribute att = (XmlEnumAttribute)info.GetCustomAttributes(typeof(XmlEnumAttribute), false)[0];
    //If there is an xmlattribute defined, return the name

    return att.Name;
}
public static T GetCode<T>(string value)
{
    // http://stackoverflow.com/a/3073272/194717
    foreach (object o in System.Enum.GetValues(typeof(T)))
    {
        T enumValue = (T)o;
        if (GetXmlAttrNameFromEnumValue<T>(enumValue).Equals(value, StringComparison.OrdinalIgnoreCase))
        {
            return (T)o;
        }
    }

    throw new ArgumentException("No XmlEnumAttribute code exists for type " + typeof(T).ToString() + " corresponding to value of " + value);
}

Answer 2

I do something similar with custom attributes and I use this method to get the EnumValue based on the Attribute Value. GetStringValue is my custom method, similar to your example above.

public static class Enums 
{ 
    public static T GetCode<T>(string value) 
    { 
        foreach (object o in System.Enum.GetValues(typeof(T))) 
        { 
            if (((Enum)o).GetStringValue().Equals(value, StringComparison.OrdinalIgnoreCase))
                return (T)o; 
        } 
        throw new ArgumentException("No code exists for type " + typeof(T).ToString() + " corresponding to value of " + value); 
    } 
}  

For the whole process I use check this post and the answers: Extending Enums, Overkill?

Sorry this is in C#, just realized you were using VB.NET above.