C# 5.0 Programmer's Reference

644 ❘ APPENDIX A Solutions to Exercises
{
}
Console.WriteLine(string.Format(format, obj.Team, obj.Score));
The query matches Team elements inside the Teams subtree with Team elements inside the
Matches subtree. For each selected pair, the query selects the team’s Name attribute and
the match result’s Score attribute.
Notice that the code compares the team and match Name attributes after converting them
into strings. The attributes themselves are XAttribute objects. They hold the same value
but the XAttribute objects are different, so if you compare those objects you’ll never find
any matches.
After selecting the corresponding records, the program loops through the query’s results
and displays the team names and scores.
5. Example program VolleyballTeamsAndTotals does this. It uses the following code to calculate
and display the teams’ total wins and points.
// Select the teams and their results.
// Total each team's wins and points.
var teamResults =
from team in root.Element("Teams").Descendants("Team")
join result in root.Element("Matches").Descendants("Team")
on team.Attribute("Name").Value
equals result.Attribute("Name").Value
group result by team into teamMatches
orderby teamMatches.Count(r => r.Attribute("Score").Value == "25") descending,
teamMatches.Sum(r => (int)r.Attribute("Score")) descending
select new
{
Team = teamMatches.Key.Attribute("Name").Value,
Wins = teamMatches.Count(r => r.Attribute("Score").Value == "25"),
Points = teamMatches.Sum(r => (int)r.Attribute("Score"))
};
string format = "{0,-20}{1,10}{2,10}";
Console.WriteLine(string.Format(format, "Name", "Wins", "Points"));
Console.WriteLine(string.Format(format, "====", "====", "======"));
foreach (var results in teamResults)
{
Console.WriteLine(string.Format(format,
results.Team, results.Wins, results.Points));
}
Like the solution to Exercise 4, this program joins teams with match results. It groups the
results by team and calls the groups teamMatches.
To determine the number of matches a team won, the query counts the matches where the
Score attribute has value 25.
To determine a team’s total number of points, the query takes the sum of the match values’
Score attribute values converted into integers.
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