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

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))

From stackoverflow

• Those are all valid and perfectly legitimate ways of checking for a selected value. Personally I find

  RadioButtonList_VolunteerType.SelectedIndex > -1
  

  to be the clearest.

• I recommend:

  RadioButtonList_VolunteerType.SelectedIndex>=0.
  

  According to the Microsoft Documentation:

  The lowest ordinal index of the selected items in the list. The default is -1, which indicates that nothing is selected.

  string.IsNullOrEmpty(RadioButtonList_VolunteerType.SelectedValue) will not always work as you can have a ListItem with an empty value:

  <asp:ListItem Value=''>This item has no value</asp:ListItem>
  

• 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
  }
  

  SkippyFire : By the way, it should be "return list.SelectedItem != null".

  Martin Clarke : good point, I'll edit the error out.