Generate A Dropdown List For Enum

We often use an Enum in C# to define all options for a field, such as a category Enum:

public enum CategoryEnum
{
    Book,
    Food,
    Tourism
}

And we need a dropdown list for this category field. How would you implement this?

Basic

First, we get all values of CategoryEnum:

Enum.GetValues(typeof(CategoryEnum))

Then, we generate all select items for these values:

Enum.GetValues(typeof(CategoryEnum)).Cast<CategoryEnum>().Select(t => new SelectListItem { Text = t.ToString(), Value = ((int)t).ToString() })

Here we use Cast<CategoryEnum>() to cast all the values so we can apply Select method on them. Finally, we have our dropdown list:

@Html.DropDownListFor(m => m.Category, Enum.GetValues(typeof(CategoryEnum)).Cast<CategoryEnum>().Select(t => new SelectListItem { Text = t.ToString(), Value = ((int)t).ToString() }), "Select one")

Custom Text

We can add descriptions to CategoryEnum and use them as the text value of each select list item.

public enum CategoryEnum
{
    [Description("Fancy Book")]
    Book,
    [Description("Delicious Food")]
    Food,
    [Description("The World Is Big")]
    Tourism
}

We then get the description with Attribute.GetCustomAttribute method. `

((DescriptionAttribute)Attribute.GetCustomAttribute((t.GetType()).GetField(t.ToString()), typeof(DescriptionAttribute))).Description

The updated code for the dropdown list would be:

@Html.DropDownListFor(m => m.Category, Enum.GetValues(typeof(CategoryEnum)).Cast<CategoryEnum>().Select(t => new SelectListItem { Text = ((DescriptionAttribute)Attribute.GetCustomAttribute((t.GetType()).GetField(t.ToString()), typeof(DescriptionAttribute))).Description, Value = ((int)t).ToString() }), "Select one")

Option Group

Sometimes we only want to display a subset of the Enum. We can define a static class for this so it can be shared everywhere.

public static class CategoryEnumGroups
{
    public static CategoryEnum[] OutdoorGroup = { CategoryEnum.Food, CategoryEnum.Tourism };
}

Then we can filter them with Where method.

Enum.GetValues(typeof(CategoryEnum)).Cast<CategoryEnum>().Where(t => CategoryEnumGroups.OutdoorGroup.Contains(t))

Final dropdown list code:

@Html.DropDownListFor(m => m.Category, Enum.GetValues(typeof(CategoryEnum)).Cast<CategoryEnum>().Where(t => CategoryEnumGroups.OutdoorGroup.Contains(t)).Select(t => new SelectListItem { Text = ((DescriptionAttribute)Attribute.GetCustomAttribute((t.GetType()).GetField(t.ToString()), typeof(DescriptionAttribute))).Description, Value = ((int)t).ToString() }), "Select one")