How to select an initial value for a DropDownList in MVC3 App

In MVC3/.NET4.0/VS2010 web application, selecting a default value for an extension method - DropDownList or DropDownListFor is tricky.

The DropDownList first parameter should be any valid name other than the list instance name.
For example, you can have DropDownList("xyz",...) not DropDownList("CompaniesRef",...), for the below example, when Model.CompaniesRef instance is used to populate the list.

Same rule applies to DropDownListFor() method too. For DropDownListFor(m=>m.Name,..), make sure the "m.Name" (actually Name) is any public "string" property in Model class.

See the example below:

PersonView.cshtml

  <table>
@model MyTestApp.Models.PersonAddressModel
  <tr>
   <!-- DONOT SELECT "HP" FROM THE LIST, INSTEAD SELECTS THE FIRST ITEM-->
   <td>@Html.DropDownList("CompaniesRef", new SelectList(
            Model.CompaniesRef,"Key","Value","HP"))
   </td>
   <td>@Html.DropDownListFor(m=>m.CompaniesRef, new SelectList(
            Model.CompaniesRef,"Key","Value","HP"))
   </td>
 
 <!-- SELECTs "HP" FROM THE LIST. THIS IS CORRECT BEHAVIOR -->
  <td>@Html.DropDownList("CompaniesRef_", new SelectList(
            Model.CompaniesRef,"Key","Value","HP"))
   </td>
   <td>@Html.DropDownListFor(m=>m.Name, new SelectList(
            Model.CompaniesRef,"Key","Value","HP"))
   </td>
   </tr>
  </table>

Model class

class Person
{
  public KeyValuePair<string, string>[] CompaniesRef { get; set; } 
  public string Name {get;set;}
  public void Load()
  {
     CompaniesRef = new KeyValuePair<string, string>[]
     {
      new KeyValuePair<string, string>("MSFT", "Microsoft"),
      new KeyValuePair<string, string>("IBM", "IBM"),
      new KeyValuePair<string, string>("HP", "HP"),
      new KeyValuePair<string, string>("GOOG", "Google"),
      new KeyValuePair<string, string>("BOA", "BANK OF AMERICA"),
      new KeyValuePair<string, string>("AMC", "American Airlines")
     };
  }
} 

Controller method

public class PersonController : Controller
 {
  public ActionResult Person(Person p)
   {
    p.Load();
    return View("PersonView",p);   
   }
 }