Question

I have a property grid that I am using for users to be able to configure objects for any plugin that is written to be used in my application. I would like to be able to tell developers writing plugins to use the ComponentModel Attributes for their members like so:

[CategoryAttribute("On Screen Display Settings"),
 DescriptionAttribute("Whether or not to show the session timer."),
 DisplayName("Show Session Timer")]
 public bool ShowTimer
 {
    get;
    set;
 }

This works great. Now I would like for the members of an enumeration to be able to be edited as well. i.e.

public enum Resolution_ : byte
{
    DCIF,
    CIF,
    QCIF,
    [DisplayName("4CIF")]
    CIF4,
    [DisplayName("2CIF")]
    CIF2
}

So that they are displayed in the PropertyGrid’s list like so:

 DCIF
 CIF
 QCIF
 CIF4
 CIF2

Along with any Descriptions and Display names they may have with them.

It seems that I can only do this with properties, events, and methods. Does anyone know how I can do this for an enumeration?

Answer 1

You will have to make an EnumConverter class and decorate your property with a TypeConverter attribute in order to do this.

See this Using PropertyGrid in .NET, it’s a fun example:

Imagine that you want more than two items in list. The boolean type is not enough; you need to set Description attributes with a name for every element in enum.

enum DrinkDoses {
  [Description("Half of litre")]
  litre,
  [Description("One litre")]
  oneLitre,
  [Description("Two litres")]
  twoLitre,
  [Description("Three litres")]
  threeLitres,
  [Description("Four litres")]
  fourLitres,
  [Description("Death dose, five litres")]
  fiveLitres
}

In another class you need to utilize the type EnumConverter.

class DrinkDosesConverter : EnumConverter {
  private Type enumType;

  public DrinkDosesConverter(Type type) : base(type) {
    enumType = type;
  }

  public override bool CanConvertTo(ITypeDescriptorContext context, Type destType) {
    return destType == typeof(string);
  }

  public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture,
                                   object value, Type destType) {
    FieldInfo fi = enumType.GetField(Enum.GetName(enumType, value));
    DescriptionAttribute dna = (DescriptionAttribute)Attribute.GetCustomAttribute(fi, 
                                typeof(DescriptionAttribute)); 
    if (dna != null)
      return dna.Description;
    else
      return value.ToString();
  }

  public override bool CanConvertFrom(ITypeDescriptorContext context, Type srcType) {
    return srcType == typeof(string);
  } 

  public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture,
                                     object value) {
    foreach (FieldInfo fi in enumType.GetFields()) {
      DescriptionAttribute dna = (DescriptionAttribute)Attribute.GetCustomAttribute(fi, 
                                  typeof(DescriptionAttribute)); 
      if ((dna != null) && ((string)value == dna.Description))
        return Enum.Parse(enumType, fi.Name);
    }
    return Enum.Parse(enumType, (string)value);
  }
}

Third, you need set the attribute TypeConverter for displaying the property.

class DrinkerDoses {
  DrinkDoses doses;
  [DisplayName("Doses")]
  [Description("Drinker doses")]
  [Category("Alcoholics drinking")]
  [TypeConverter(typeof(DrinkDosesConverter))]
  public DrinkDoses Doses {
    get { return doses; }
    set { doses = value; }
  }
  int dataInt; 
  public int DataInt {
    get { return dataInt; }
    set { dataInt = value; }
  }
}