How to get Custom Attribute values for enums?

Question

I have an enum where each member has a custom attribute applied to it. How can I retrieve the value stored in each attribute?

Right now I do this:

va         


        

Answer 1

Assuming GPUShaderAttribute:

[AttributeUsage(AttributeTargets.Field,AllowMultiple =false)]
public class GPUShaderAttribute: Attribute
{
    public GPUShaderAttribute(string value)
    {
        Value = value;
    }
    public string Value { get; internal set; }
}

Then we could write a few generic methods to return a dictionary of the enum values and the GPUShaderAttribute object.

    /// 

    /// returns the attribute for a given enum
    /// 
        
    public static TAttribute GetAttribute(IConvertible @enum)
    {
        TAttribute attributeValue = default(TAttribute);
        if (@enum != null)
        {
            FieldInfo fi = @enum.GetType().GetField(@enum.ToString());
            attributeValue = fi == null ? attributeValue : (TAttribute)fi.GetCustomAttributes(typeof(TAttribute), false).DefaultIfEmpty(null).FirstOrDefault();

        }
        return attributeValue;
    }

Then return the whole set with this method.

/// 

/// Returns a dictionary of all the Enum fields with the attribute.
/// 
public static Dictionary GetEnumObjReference()
{
    Dictionary _dict = new Dictionary();
    Type enumType = typeof(TEnum);
    Type enumUnderlyingType = Enum.GetUnderlyingType(enumType);
    Array enumValues = Enum.GetValues(enumType);
    foreach (Enum enumValue in enumValues)
    {
        _dict.Add(enumValue, GetAttribute(enumValue));
    }

    return _dict;
}

If you just wanted a string value I would recommend a slightly different route.

    /// 

    /// Returns the string value of the custom attribute property requested.
    /// 
    public static string GetAttributeValue(IConvertible @enum, string propertyName = "Value")
    {
        TAttribute attribute = GetAttribute(@enum);
        return attribute == null ? null : attribute.GetType().GetProperty(propertyName).GetValue(attribute).ToString();

    }

    /// 

    /// Returns a dictionary of all the Enum fields with the string of the property from the custom attribute nulls default to the enumName
    /// 
    public static Dictionary GetEnumStringReference(string propertyName = "Value")
    {
        Dictionary _dict = new Dictionary();
        Type enumType = typeof(TEnum);
        Type enumUnderlyingType = Enum.GetUnderlyingType(enumType);
        Array enumValues = Enum.GetValues(enumType);
        foreach (Enum enumValue in enumValues)
        {
            string enumName = Enum.GetName(typeof(TEnum), enumValue);
            string decoratorValue = Common.GetAttributeValue(enumValue, propertyName) ?? enumName;
            _dict.Add(enumValue, decoratorValue);
        }

        return _dict;
    }