Binding a Control to an Enum

Imagine you have an enum defined in your code like so:

enum ContractType
{
    Permanent = 1,
    Contract = 2,
    Internship = 99
}

Suppose we have a DropDownList on an ASP.NET page from which we'd like the user to select the appropriate ContractType.

<asp:DropDownList runat="server" DataTextField="Key" DataValueField="Value" id="MyDropDownList">

Obviously, we can't do something as simple as

MyDropDownList.DataSource = ContractType;

as ContractType is a type, not an object. Instead, we can create a simple helper function that uses the Enum.GetValues and Enum.GetNames methods in order to create a Hashtable object (consisting of keys - Permanent, Contract, etc, and values - 1, 2 etc).

public static Hashtable BindToEnum(Type enumType)
{
    // get the names from the enumeration
    string[] names = Enum.GetNames(enumType);
    // get the values from the enumeration
    Array values = Enum.GetValues(enumType);
    // turn it into a hash table
    Hashtable ht = new Hashtable();
    for (int i = 0; i < names.Length; i++)
        // note the cast to integer here is important
        // otherwise we'll just get the enum string back again
        ht.Add(names[i], (int)values.GetValue(i));
    // return the dictionary to be bound to
    return ht;
}

You can then use this as follows:

MyDropDownList.DataSource = BindToEnum(typeof(ContractType));

and we get a drop down list bound to the appropriate names/values as defined by the enum (note that we specified DataTextField and DataValueField in the earlier DropDownList definition).

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James Crowley James first started this website when learning Visual Basic back in 1999 whilst studying his GCSEs. The site grew steadily over the years while being run as a hobby - to a regular monthly audience ...

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