var query = (from int n in Enum.GetValues(typeof(System.Windows.Forms.DialogResult))
 			 select new {
						 n,
	 					 Key = Enum.GetName(typeof(System.Windows.Forms.DialogResult),n) 
 						}
			);

comboBox1.DataSource = query.ToList();
comboBox1.DisplayMember = "key";
comboBox1.ValueMember = "n";

Bind Enum to Combobox

C#