How to bind a custom Enum description to a DataGrid

Question

Problem: I have an enumerated type which has description tags in the following style: [URL="http://xml.indelv.com/data-binding-enum.html"]description tag tutorial[/URL] . I have a Windows SQL Server Database from which I am pulling the data (as integers then castine to Enums) which is then being bound to a datagrid. Instead of pulling and casing the enumerated types, I would like to display the description tag associated with it in the enumerated type.

Here is the ASP -

<asp:GridView ID="StatementGrid" runat="server" AutoGenerateColumns="false" DataKeyNames="statementID" OnRowDeleting="StatementGrid_onDeleting" AllowSorting="False">
                <Columns>
                    <asp:BoundField HeaderText="Type" SortExpression="type" DataField="TypeOfStatement" />
                    <asp:HyperLinkField HeaderText="Statement" DataTextField="StatementText" DataNavigateUrlFormatString="~/Gateway/Statements/View.aspx?statementID={0}" SortExpression="statement" DataNavigateUrlFields="statementID" />
                    <asp:HyperLinkField DataNavigateUrlFields="statementID" DataNavigateUrlFormatString="~/Gateway/Statements/Update.aspx?statementID={0}" NavigateUrl="~/Gateway/Statements/Update.aspx" HeaderText="Edit" Text="<img src='../../Images/News/news_edit.gif' alt='Edit Statement'/>" />
                    <asp:TemplateField HeaderText="Delete">
                        <ItemTemplate>
                            <asp:ImageButton AlternateText="Delete Statement" ID="DeleteButton" ImageUrl="~/Images/News/news_delete.gif" runat="server" CommandName="Delete" OnClientClick="javascript:return confirm('Are you sure you want to delete this statement?');" />
                        </ItemTemplate>
                    </asp:TemplateField>
                </Columns>
                <EmptyDataTemplate>
                    There are no statements to display.
                </EmptyDataTemplate>
            </asp:GridView>

Here is the code for the Bind -

[CODE]

private void BindData()
        {
            IStatementDao statementDao = DaoFactory.GetStatementDao();
            List<Statement> statements;

            if (Page.Request.RawUrl.Contains("Gateway"))
            {
                statements = statementDao.GetAll();

                StatementGrid.HeaderStyle.CssClass = "GatewayGridHeader";
                StatementGrid.AlternatingRowStyle.CssClass = "GatewayGridAlternatingRow";

            }
            else
            {
                // This should never be reached but it keeps the compiler happy!!
                statements = statementDao.GetAll();
            }

            StatementGrid.DataSource = statements;
            StatementGrid.DataBind();
            DisplayTypeDescriptors();
        }

[/CODE]

Here is the enumerated class -

[CODE]

public enum TypeOfStatement 
        { 
            [EnumDescription("Dress Code")] DressCode = 1,
            [EnumDescription("Lunch Time")] LunchTime = 2,
            [EnumDescription("Footwarez")] Footware = 3,
            [EnumDescription("achtung")] Warning = 4,
            [EnumDescription("Banarna")] Banana = 5,
            [EnumDescription("Apfel")] Apple = 6
        };c#

[/CODE]

Its obvious that one could write an extensive method do do what i want, but is there a neater way?

Answer 1

Wrap them up on the fly and subtly change your handling of the SelectedItem (or whatever you are using)
My example uses the already present Description attribute.

public class DescriptiveEnum<T> where T: struct
{
    private static readonly Dictionary<T,string> descriptions 
        = new Dictionary<T,string>();

    static DescriptiveEnum()
    {
        foreach (FieldInfo field in
            typeof(T).GetFields(BindingFlags.Static 
            | BindingFlags.GetField | BindingFlags.Public))
        {
        descriptions.Add((T)field.GetRawConstantValue(),
            LookupName(field));         
        }
    }

    public readonly T Value;

    public DescriptiveEnum(T value)
    {
        this.Value = value;     
    }

    public override string ToString()
    {
        string s;
        if (!descriptions.TryGetValue(this.Value, out s))
        {           
        // fall back for non declared fields
        s = this.Value.ToString();  
        descriptions[this.Value] = s;
        }
        return s;
    }

    private static string LookupName(FieldInfo field)        
    {
        object[] all = field.GetCustomAttributes(
             typeof(DescriptionAttribute), false);
        if (all.Length == 0)
            return field.Name; // fall back
        else
            return ((DescriptionAttribute)all[0])
                .Description; // only one needed
    }   

    public static BindingList<DescriptiveEnum<T>> Make(
        IEnumerable<T> source)
    {
        var list = new BindingList<DescriptiveEnum<T>>();
        foreach (var x in source)
        list.Add(new DescriptiveEnum<T>(x));
        return list;
    }
}

example usage:

public enum Foo
{
    [Description("flibble")]
    Bar,
    [Description("wobble")]
    Baz,
    // none present, will use the name
    Bat

}

Form f = new Form();
f.Controls.Add(new ListBox() 
{
    Dock = DockStyle.Fill,
    DataSource = DescriptiveEnum<Foo>.Make(
       new Foo[] { Foo.Bar, Foo.Baz, Foo.Bat }),
});
Application.Run(f);