How to walk through a SelectListItem Array with Linq - techniques?

Linq – Newbie question:

string[] grades = { "2", "5", "1", "7", "4", "8", "6", "0", "9", "3" };

List<SelectListItem> xValues = new List<SelectListItem>() 
                                   {  new SelectListItem 
                                          { Selected = true,
                                            Text = "Select...",
                                            Value = "Select...",
                                          }
                                   };

for (int a = 0; a < 10; a++)
{
      xValues.Add(new SelectListItem
                      { Selected = false,
                        Text = grades[a],
                        Value = grades[a]
                      }
                 );
}

My application works very fine up to this point. xValues contains now 11 elements. Each element contains a "Selected", "Text" and "Value" property. "Selected" is only in the first element set to "true". The second elements contains a "2" in "Text" and "Value", the third element contains a “5”, the fourth contains a “1” and so on...

Question: 开发者_StackOverflow中文版How to set "Selected" to "true" in that xValue element which contains a "5" in the "Text" (and in the "Value") property?

Note, that not the 6th element contains (necessarily) the searched "5"!

I believe it must be something like that:

for (int i = 0; i < ponyValues.Count(); i++)
{
  xValues[i].Selected = false;
  if (xValues.First().Value == “5”)
  {
   xValues[i].Selected = true;
  }
}

Of course is ".First()" wrong... but what would be correct?

var five = xValues.FirstOrDefault(x=> x.Value == "5");
if (five != null)
    five.Selected = true;

SelectListItem item = xValues.Single(item => item.Value == 5);
item.Selected = true;

Please note that this will throw an exception if there isn't exactly one item with a value of 5.

var xValues = grades.Select(g => new SelectListItem
                                 {
                                     Selected = (g == "5")
                                     Text = g,
                                     Value = g
                                 })
                    .ToList();

xValues.Insert(0, new SelectListItem 
                  {
                      Selected = false,
                      Text = "Select...",
                      Value = "Select...",
                  });

Thanks to all! Finally I do this

var isSelected = xValues.FirstOrDefault(x => x.Selected == true);
var mustBeSelected = xValues.FirstOrDefault(x => x.Value == "5");
if ((isSelected != null) && (mustBeSelected != null))
{
    isSelected.Selected = false;
    mustBeSelected.Selected = true;
}

because I want also to set "Selected" to "false" for the very first element. Sorry forgot to you tell this ;-)