Bind a Combo Box to an Enumeration in Visual Studio .NET

Provided by Jim Ferguson, Project Manager

An enumeration is a related set of constants. The enumeration members between the Enum and End Enum statements are initialized to constant values. Enumeration is used to group a set of constants under a common name, so the value can be referred to by a string value rather than the numeric value.

For example, this enumeration provides a list of constants for the provided names:

    Private Enum PeopleNames

        bob

        mary

        jane

        joe

        fred

    End Enum

By default, the first enumerator has a value of 0, and each successive enumerator is one larger than the value of the previous one, unless you explicitly specify a value for a particular enumerator. The value for "bob" is 0, "mary" is 1, and so on to "fred" which is 4.

It is possible to bind a combo box or a list box to the values in the enumeration so that the values in the dropdown list are the string names, but the underlying constant values can be retrieved from the selected item. The Enum class provides a static method called "GetValues" which returns an array of all items in the enumeration. You can bind a combo box to this enumeration with code such as the following:

Me.ComboBox1.DataSource = _

System.Enum.GetValues(GetType(PeopleNames))

The argument to GetValues is a type value for the enumeration you wish to retrieve. GetType returns a type object based on the name of the enumeration. Change this value to the name of the enum you are interested in.

After this line of code executes the list portion of the combo box contains the names "bob", "mary", "jane" etc. If you just want to know which name was selected you can use the .SelectedText property of the combobox. However if you want to know the constant value associated with the name, you need to use the .SelectedValue property (which is a generic object) and cast it to the type of enum you are interested in.

For example:

    Dim nameid As PeopleNames = CType(ComboBox1.SelectedValue, PeopleNames)

The variable "nameid" contains a 0, or 1, or 2 etc. depending on the value of the enumerated item that is currently selected.