Attributes and Named/Optional constructor parameters not working

Question

I have custom attribute defined like so:

  [AttributeUsage(AttributeTargets.Field)]
  public class EnumDisplayAttribute : Attribute
  {
    public string Des         


        

Answer 1

If you do want to push values into your attribute using a constructor (e.g. if some of your attribute's properties are mandatory or to perform some kind of processing on them) you can always go old school and overload the constructor.

For example:

[AttributeUsage(AttributeTargets.Field)]
public class SampleAttribute : Attribute
{
    public string MandatoryProperty { get; private set; }
    public string OptionalProperty { get; private set; }

    // we use an overload here instead of optional parameters because 
    // C# does not currently support optional constructor parameters in attributes
    public SampleAttribute(string mandatoryProperty)
        : this(mandatoryProperty, null)
    {
    }

    public SampleAttribute(string mandatoryProperty, string optionalProperty)
    {
        MandatoryProperty = mandatoryProperty;
        OptionalProperty = optionalProperty;
    }
}