class CompoundFrom
{// The element type of the data source.public class Student{public string LastName { get; set; }public List<int> Scores {get; set;}}static void Main(){// Use a collection initializer to create the data source. Note that // each element in the list contains an inner sequence of scores.List<Student> students = new List<Student>{new Student {LastName="Omelchenko", Scores= new List<int> {97, 72, 81, 60}},new Student {LastName="O'Donnell", Scores= new List<int> {75, 84, 91, 39}},new Student {LastName="Mortensen", Scores= new List<int> {88, 94, 65, 85}},new Student {LastName="Garcia", Scores= new List<int> {97, 89, 85, 82}},new Student {LastName="Beebe", Scores= new List<int> {35, 72, 91, 70}} };        // Use a compound from to access the inner sequence within each element.// Note the similarity to a nested foreach statement.var scoreQuery = from student in studentsfrom score in student.Scoreswhere score > 90select new { Last = student.LastName, score };// Execute the queries.Console.WriteLine("scoreQuery:");// Rest the mouse pointer on scoreQuery in the following line to // see its type. The type is IEnumerable<'a>, where 'a is an // anonymous type defined as new {string Last, int score}. That is,// each instance of this anonymous type has two members, a string // (Last) and an int (score).foreach (var student in scoreQuery){Console.WriteLine("{0} Score: {1}", student.Last, student.score);}// Keep the console window open in debug mode.Console.WriteLine("Press any key to exit.");Console.ReadKey();}
}
/*
scoreQuery:
Omelchenko Score: 97
O'Donnell Score: 91
Mortensen Score: 94
Garcia Score: 97
Beebe Score: 91
*/

class CompoundFrom2
{static void Main(){char[] upperCase = { 'A', 'B', 'C' };char[] lowerCase = { 'x', 'y', 'z' };// The type of joinQuery1 is IEnumerable<'a>, where 'a// indicates an anonymous type. This anonymous type has two// members, upper and lower, both of type char.var joinQuery1 =from upper in upperCasefrom lower in lowerCaseselect new { upper, lower };// The type of joinQuery2 is IEnumerable<'a>, where 'a// indicates an anonymous type. This anonymous type has two// members, upper and lower, both of type char.var joinQuery2 =from lower in lowerCasewhere lower != 'x'from upper in upperCaseselect new { lower, upper };// Execute the queries.Console.WriteLine("Cross join:");// Rest the mouse pointer on joinQuery1 to verify its type.foreach (var pair in joinQuery1){Console.WriteLine("{0} is matched to {1}", pair.upper, pair.lower);}Console.WriteLine("Filtered non-equijoin:");// Rest the mouse pointer over joinQuery2 to verify its type.foreach (var pair in joinQuery2){Console.WriteLine("{0} is matched to {1}", pair.lower, pair.upper);}// Keep the console window open in debug mode.Console.WriteLine("Press any key to exit.");Console.ReadKey();}
}
/* Output:Cross join:A is matched to xA is matched to yA is matched to zB is matched to xB is matched to yB is matched to zC is matched to xC is matched to yC is matched to zFiltered non-equijoin:y is matched to Ay is matched to By is matched to Cz is matched to Az is matched to Bz is matched to C*/