Find Index of a Node in XML using LINQ

string xmlData = @"<ProjectedIncomePosition><Coupon>0.59</Coupon><IsExternal>false</IsExternal><MaturityDate/></ProjectedIncomePosition>";

// Getting all elements.
IEnumerable<XElement> roots = XElement.Parse(xmlData).Elements();

// Getting coupon node index
int coupon = roots.Select((item, index) => new { elementName = item.Name, Index = index }).Where(p => p.elementName == "Coupon").Select(p => p.Index + 1).FirstOrDefault();

// Getting maturity node index
int maturityDate = roots.Select((item, index) => new { elementName = item.Name, Index = index }).Where(p => p.elementName == "MaturityDate").Select(p => p.Index + 1).FirstOrDefault();

if (coupon < maturityDate)
{
    // Correct
}
else
{
    // Incorrect data
}