Question

Let’s say I have an Order class that has properties such as OrderName, OrderNum , etc…

then to populate a ComboBox with a list of items from this class, let’s say I do it like this:

comboBox1.DisplayMember = "OrderName";
comboBox1.ValueMember = "OrderNum";
comboBox1.DataSource = list.ToArray<Order>();

So here I am hard coding the name of those fields in the code such as “OrderName”. Is there a better way of doing this rather than hard coding the name of the fields? Does it need some sort of dependency injection tricks? What do you suggest?

Answer 1

Below is a modified class I use in several of my ASP.NET applications. The way I’d assign it in your sample is like this:

var orders = model.GetOrders(...);

comboBox1.DisplayMember = OrderQueryResults.DisplayMember;
comboBox1.ValueMember = OrderQueryResults.ValueMember;
comboBox1.DataSource = orders.Results;

Class:

public sealed class OrderQueryResults : IOrderQueryResults
{
    private const string DisplayName = "OrderName";

    private const string ValueName = "OrderNum";

    private readonly IEnumerable<IOrderQueryResult> results;

    private readonly object extra;

    private OrderQueryResults(IEnumerable<IOrderQueryResult> results, object extra)
    {
        this.results = results;
        this.extra = extra;
    }

    public string DisplayMember
    {
        get
        {
            return DisplayName;
        }
    }

    public string ValueMember
    {
        get
        {
            return ValueName;
        }
    }

    public IEnumerable<IOrderQueryResult> Results
    {
        get
        {
            return this.results;
        }
    }

    public object Extra
    {
        get
        {
            return this.extra;
        }
    }

    public static IOrderQueryResults Create(IEnumerable<IOrderQueryResult> results, object extra)
    {
        if (results == null)
        {
            throw new ArgumentNullException("results");
        }

        return new OrderQueryResults(results.ToList(), extra);
    }
}