Csharp/C Sharp/LINQ/ToList — различия между версиями
Admin (обсуждение | вклад) м (1 версия) |
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Версия 18:31, 26 мая 2010
Содержание
Calling the ToList Operator
<source lang="csharp"> using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class MainClass {
public static void Main() { string[] presidents = {"G", "H", "a", "H", "over", "Jack"}; List<string> names = presidents.ToList(); foreach (string name in names) Console.WriteLine(name); }
}
</source>
calling ToList.
<source lang="csharp"> using System; using System.Collections.Generic; using System.Linq; public class MainClass {
public static void Main() { var numbers = new List<int>() { 1, 2 }; List<int> timesTen = numbers .Select(n => n * 10) .ToList(); numbers.Clear(); Console.WriteLine(timesTen.Count); }
}
</source>
Convert an ArrayList to an IEnumerable<T> That Can Be Used with the Typical Standard Query Operators
<source lang="csharp"> using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class Employee {
public int id; public string firstName; public string lastName; public static ArrayList GetEmployeesArrayList() { ArrayList al = new ArrayList(); al.Add(new Employee { id = 1, firstName = "J", lastName = "R" }); al.Add(new Employee { id = 2, firstName = "W", lastName = "G" }); al.Add(new Employee { id = 3, firstName = "A", lastName = "H" }); al.Add(new Employee { id = 4, firstName = "D", lastName = "L" }); al.Add(new Employee { id = 101, firstName = "K", lastName = "F" }); return (al); } public static Employee[] GetEmployeesArray() { return ((Employee[])GetEmployeesArrayList().ToArray(typeof(Employee))); }
} public class MainClass {
public static void Main() { ArrayList employees = Employee.GetEmployeesArrayList(); Console.WriteLine("The data type of employees is " + employees.GetType()); var seq = employees.Cast<Employee>(); Console.WriteLine("The data type of seq is " + seq.GetType()); var emps = seq.OrderBy(e => e.lastName); foreach (Employee emp in emps) Console.WriteLine("{0} {1}", emp.firstName, emp.lastName); }
}
</source>
Convert Query result to a List
<source lang="csharp"> using System; using System.Collections; using System.Collections.Generic; using System.Text; using System.Linq; class Employee {
int _id; int _idRole; string _lastName; string _firstName; public int ID { get { return _id; } set { _id = value; } } public int IDRole { get { return _idRole; } set { _idRole = value; } } public string LastName { get { return _lastName; } set { _lastName = value; } } public string FirstName { get { return _firstName; } set { _firstName = value; } }
} public class MainClass {
public static void Main() { List<Employee> people = new List<Employee> { new Employee { ID = 1, IDRole = 1, LastName = "A", FirstName = "B"}, new Employee { ID = 2, IDRole = 2, LastName = "G", FirstName = "T"} }; var query = from p in people where p.LastName.Length == 4 select p.LastName; List<string> names = query.ToList<string>(); Console.Write(names); }
}
</source>