How to Fill a ListBox/DropDownList from an Enum

There was a question about this on the Asp.Net forums and after a quick search I didn't find a good generic function so I thought I'd supply one.

Note: I wanted this to be as broad and useful as possible, so the second parameter is a ListControl which both the ListBox and DropDownList inherit from.

I also made sure the function would handle enums that had non-contiguous values that didn't necessarily start at zero.

The function: 

// ---- EnumToListBox ------------------------------------
//
// Fills List controls (ListBox, DropDownList) with the text 
// and value of enums
//
// Usage:  EnumToListBox(typeof(MyEnum), ListBox1);
 
static public void EnumToListBox(Type EnumType, ListControl TheListBox)
{
    Array Values = System.Enum.GetValues(EnumType);
 
    foreach (int Value in Values)
    {
        string Display = Enum.GetName(EnumType, Value);
        ListItem Item = new ListItem(Display, Value.ToString());
        TheListBox.Items.Add(Item);
    }
}
 

Usage:  

I tested with an existing enum and a custom enum: 

enum CustomColors
{
    BLACK = -1,
    RED = 7,
    GREEN = 14,
    UNKNOWN = -13
}
 
protected void Button1_Click(object sender, EventArgs e)
{
    EnumToListBox(typeof(DayOfWeek), DropDownList1);
 
    EnumToListBox(typeof(CustomColors), ListBox1);
}

Note: I initially tried to get the order of the items in the ListBox to match the order of the items in the enum but both the Enum.GetValues and Enum.GetNames functions return the items sorted by the value of the enum. So if you want the enums sorted a certain way, the values of the enums must be sorted that way. I think this is reasonable; how the enums are physically sorted in the source code shouldn't necessarily have any meaning.

I hope someone finds this useful.

3 Comments

  • You could use an Extension Method on a ListControl to create a new method. This would allow you to create code that looks like this:

    DropDownList.BindToEnum(typeof(enum));

    Doesn't make it any more or less functional, just a bit prettier.

  • It could be abstracted a step farther by returning a tuple with the value and display name. Then it would not only be limited too a ListBoxControl.

  • You can go a step further and add a "Description" attribute (System.ComponentModel) to each enumerated value.

    enum CustomColors
    {
    [Description("Yellow Green")]
    YellowGreen = 13,
    [Description("Burnt Orange")]
    BurntOrange = 14,
    [Description("Violet (Purple)")]
    Purple = 15,
    }

    Then you can add to your code a check to see if the enumerated values have a description using:

    GetCustomAttributes( typeof( DescriptionAttribute ), false )


    I've written code to take the name and separate into words based on camel case as well. Then you don't need the Description attributes for the simple cases.

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