What is the best way to see if a RadioButtonList has a selected value?

Question

I am using:

if (RadioButtonList_VolunteerType.SelectedItem != null)

or how about:

if (RadioButtonList_VolunteerType.Index >= 0)

or how about (per Andrew Hare's answer):

if (RadioButtonList_VolunteerType.Index > -1)

To those who may read this question, the following is not a valid method. As Keltex pointed out, the selected value could be an empty string.

if (string.IsNullOrEmpty(RadioButtonList_VolunteerType.SelectedValue))

Answer 1

In terms of readability they all lack something for me. This seems like a good candidate for an extension method.

public static class MyExtenstionMethods 
{   
  public static bool HasSelectedValue(this RadioButtonList list) 
  {
    return list.SelectedItem != null;
  }
}


...

if (RadioButtonList_VolunteerType.HasSelectedValue)
{
 // do stuff
}