using System; using System.Linq; using System.Collections; using System.Collections.Generic; public class MainClass { public static void Main() { string[] presidents = {"lore", "Truman", "Tailer", "Van", "Washington", "Wilson"}; IEnumerable<string> items = presidents.Reverse(); foreach (string item in items) Console.WriteLine(item); } }
LINQ
Reverse does exactly as it says
using System; using System.Collections.Generic; using System.Linq; public class MainClass { public static void Main() { int[] numbers = { 10, 9, 8, 7, 6 }; IEnumerable<int> reversed = numbers.Reverse(); // { 6, 7, 8, 9, 10 } } }
Restriction Operators: Use where clause with int array element
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
public static void Main() {
int[] numbers = { 5, 4, 1, 3, 9};
var lowNums =
from n in numbers
where n < 5
select n;
Console.WriteLine("Numbers < 5:");
foreach (var x in lowNums) {
Console.WriteLine(x);
}
}
}
[/csharp]
All employees in a tree are grouped by department
using System; using System.Collections.Generic; using System.Linq; using System.Text; public class Tree<TreeNode> : IEnumerable<TreeNode> where TreeNode : IComparable<TreeNode> { public Tree(TreeNode nodeValue) { this.NodeData = nodeValue; this.LeftTree = null; this.RightTree = null; } public void Insert(TreeNode newItem) { TreeNode currentNodeValue = this.NodeData; if (currentNodeValue.CompareTo(newItem) > 0) { if (this.LeftTree == null) { this.LeftTree = new Tree<TreeNode>(newItem); } else { this.LeftTree.Insert(newItem); } } else { if (this.RightTree == null) { this.RightTree = new Tree<TreeNode>(newItem); } else { this.RightTree.Insert(newItem); } } } public void WalkTree() { if (this.LeftTree != null) { this.LeftTree.WalkTree(); } Console.WriteLine(this.NodeData.ToString()); if (this.RightTree != null) { this.RightTree.WalkTree(); } } public TreeNode NodeData { get; set; } public Tree<TreeNode> LeftTree { get; set; } public Tree<TreeNode> RightTree { get; set; } IEnumerator<TreeNode> IEnumerable<TreeNode>.GetEnumerator() { if (this.LeftTree != null) { foreach (TreeNode item in this.LeftTree) { yield return item; } } yield return this.NodeData; if (this.RightTree != null) { foreach (TreeNode item in this.RightTree) { yield return item; } } } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw new NotImplementedException(); } } class Employee : IComparable<Employee> { public string FirstName { get; set; } public string LastName { get; set; } public string Department { get; set; } public int Id { get; set; } public override string ToString() { return String.Format("Id: {0}, Name: {1} {2}, Dept: {3}", this.Id, this.FirstName, this.LastName, this.Department); } int IComparable<Employee>.CompareTo(Employee other) { if (other == null) return 1; if (this.Id > other.Id) return 1; if (this.Id < other.Id) return -1; return 0; } } class Program { static void Main() { Tree<Employee> empTree = new Tree<Employee>(new Employee { Id = 1, FirstName = "Janet", LastName = "Gates", Department = "IT" }); empTree.Insert(new Employee { Id = 2, FirstName = "O", LastName = "G", Department = "Marketing" }); empTree.Insert(new Employee { Id = 4, FirstName = "K", LastName = "H", Department = "IT" }); empTree.Insert(new Employee { Id = 6, FirstName = "L", LastName = "H", Department = "Sales" }); empTree.Insert(new Employee { Id = 3, FirstName = "E", LastName = "L", Department = "Sales" }); empTree.Insert(new Employee { Id = 5, FirstName = "D", LastName = "L", Department = "Marketing" }); var employeesByDept = empTree.GroupBy(e => e.Department); foreach (var dept in employeesByDept) { Console.WriteLine("Department: {0}", dept.Key); foreach (var emp in dept) { Console.WriteLine(" {0} {1}", emp.FirstName, emp.LastName); } } } }
Use from where select to choose the Employees in the IT department from a tree
using System; using System.Collections.Generic; using System.Linq; using System.Text; public class Tree<TreeNode> : IEnumerable<TreeNode> where TreeNode : IComparable<TreeNode> { public Tree(TreeNode nodeValue) { this.NodeData = nodeValue; this.LeftTree = null; this.RightTree = null; } public void Insert(TreeNode newItem) { TreeNode currentNodeValue = this.NodeData; if (currentNodeValue.CompareTo(newItem) > 0) { if (this.LeftTree == null) { this.LeftTree = new Tree<TreeNode>(newItem); } else { this.LeftTree.Insert(newItem); } } else { if (this.RightTree == null) { this.RightTree = new Tree<TreeNode>(newItem); } else { this.RightTree.Insert(newItem); } } } public void WalkTree() { if (this.LeftTree != null) { this.LeftTree.WalkTree(); } Console.WriteLine(this.NodeData.ToString()); if (this.RightTree != null) { this.RightTree.WalkTree(); } } public TreeNode NodeData { get; set; } public Tree<TreeNode> LeftTree { get; set; } public Tree<TreeNode> RightTree { get; set; } IEnumerator<TreeNode> IEnumerable<TreeNode>.GetEnumerator() { if (this.LeftTree != null) { foreach (TreeNode item in this.LeftTree) { yield return item; } } yield return this.NodeData; if (this.RightTree != null) { foreach (TreeNode item in this.RightTree) { yield return item; } } } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw new NotImplementedException(); } } class Employee : IComparable<Employee> { public string FirstName { get; set; } public string LastName { get; set; } public string Department { get; set; } public int Id { get; set; } public override string ToString() { return String.Format("Id: {0}, Name: {1} {2}, Dept: {3}", this.Id, this.FirstName, this.LastName, this.Department); } int IComparable<Employee>.CompareTo(Employee other) { if (other == null) return 1; if (this.Id > other.Id) return 1; if (this.Id < other.Id) return -1; return 0; } } class Program { static void Main() { Tree<Employee> empTree = new Tree<Employee>(new Employee { Id = 1, FirstName = "Janet", LastName = "Gates", Department = "IT" }); empTree.Insert(new Employee { Id = 2, FirstName = "O", LastName = "G", Department = "Marketing" }); empTree.Insert(new Employee { Id = 4, FirstName = "K", LastName = "H", Department = "IT" }); empTree.Insert(new Employee { Id = 6, FirstName = "L", LastName = "H", Department = "Sales" }); empTree.Insert(new Employee { Id = 3, FirstName = "E", LastName = "L", Department = "Sales" }); empTree.Insert(new Employee { Id = 5, FirstName = "D", LastName = "L", Department = "Marketing" }); var ITEmployees = from e in empTree where String.Equals(e.Department, "IT") select e; foreach (var emp in ITEmployees) Console.WriteLine(emp); } }
Use LINQ to get Employees in the IT department from a tree
using System; using System.Collections.Generic; using System.Linq; using System.Text; public class Tree<TreeNode> : IEnumerable<TreeNode> where TreeNode : IComparable<TreeNode> { public Tree(TreeNode nodeValue) { this.NodeData = nodeValue; this.LeftTree = null; this.RightTree = null; } public void Insert(TreeNode newItem) { TreeNode currentNodeValue = this.NodeData; if (currentNodeValue.CompareTo(newItem) > 0) { if (this.LeftTree == null) { this.LeftTree = new Tree<TreeNode>(newItem); } else { this.LeftTree.Insert(newItem); } } else { if (this.RightTree == null) { this.RightTree = new Tree<TreeNode>(newItem); } else { this.RightTree.Insert(newItem); } } } public void WalkTree() { if (this.LeftTree != null) { this.LeftTree.WalkTree(); } Console.WriteLine(this.NodeData.ToString()); if (this.RightTree != null) { this.RightTree.WalkTree(); } } public TreeNode NodeData { get; set; } public Tree<TreeNode> LeftTree { get; set; } public Tree<TreeNode> RightTree { get; set; } IEnumerator<TreeNode> IEnumerable<TreeNode>.GetEnumerator() { if (this.LeftTree != null) { foreach (TreeNode item in this.LeftTree) { yield return item; } } yield return this.NodeData; if (this.RightTree != null) { foreach (TreeNode item in this.RightTree) { yield return item; } } } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw new NotImplementedException(); } } class Employee : IComparable<Employee> { public string FirstName { get; set; } public string LastName { get; set; } public string Department { get; set; } public int Id { get; set; } public override string ToString() { return String.Format("Id: {0}, Name: {1} {2}, Dept: {3}", this.Id, this.FirstName, this.LastName, this.Department); } int IComparable<Employee>.CompareTo(Employee other) { if (other == null) return 1; if (this.Id > other.Id) return 1; if (this.Id < other.Id) return -1; return 0; } } class Program { static void Main() { Tree<Employee> empTree = new Tree<Employee>(new Employee { Id = 1, FirstName = "Janet", LastName = "Gates", Department = "IT" }); empTree.Insert(new Employee { Id = 2, FirstName = "O", LastName = "G", Department = "Marketing" }); empTree.Insert(new Employee { Id = 4, FirstName = "K", LastName = "H", Department = "IT" }); empTree.Insert(new Employee { Id = 6, FirstName = "L", LastName = "H", Department = "Sales" }); empTree.Insert(new Employee { Id = 3, FirstName = "E", LastName = "L", Department = "Sales" }); empTree.Insert(new Employee { Id = 5, FirstName = "D", LastName = "L", Department = "Marketing" }); var ITEmployees = empTree.Where(e => String.Equals(e.Department, "IT")).Select(emp => emp); foreach (var emp in ITEmployees) Console.WriteLine(emp); } }
Get Distinct departments with condition
using System; using System.Collections.Generic; using System.Linq; using System.Text; public class Tree<TreeNode> : IEnumerable<TreeNode> where TreeNode : IComparable<TreeNode> { public Tree(TreeNode nodeValue) { this.NodeData = nodeValue; this.LeftTree = null; this.RightTree = null; } public void Insert(TreeNode newItem) { TreeNode currentNodeValue = this.NodeData; if (currentNodeValue.CompareTo(newItem) > 0) { if (this.LeftTree == null) { this.LeftTree = new Tree<TreeNode>(newItem); } else { this.LeftTree.Insert(newItem); } } else { if (this.RightTree == null) { this.RightTree = new Tree<TreeNode>(newItem); } else { this.RightTree.Insert(newItem); } } } public void WalkTree() { if (this.LeftTree != null) { this.LeftTree.WalkTree(); } Console.WriteLine(this.NodeData.ToString()); if (this.RightTree != null) { this.RightTree.WalkTree(); } } public TreeNode NodeData { get; set; } public Tree<TreeNode> LeftTree { get; set; } public Tree<TreeNode> RightTree { get; set; } IEnumerator<TreeNode> IEnumerable<TreeNode>.GetEnumerator() { if (this.LeftTree != null) { foreach (TreeNode item in this.LeftTree) { yield return item; } } yield return this.NodeData; if (this.RightTree != null) { foreach (TreeNode item in this.RightTree) { yield return item; } } } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw new NotImplementedException(); } } class Employee : IComparable<Employee> { public string FirstName { get; set; } public string LastName { get; set; } public string Department { get; set; } public int Id { get; set; } public override string ToString() { return String.Format("Id: {0}, Name: {1} {2}, Dept: {3}", this.Id, this.FirstName, this.LastName, this.Department); } int IComparable<Employee>.CompareTo(Employee other) { if (other == null) return 1; if (this.Id > other.Id) return 1; if (this.Id < other.Id) return -1; return 0; } } class Program { static void Main() { Tree<Employee> empTree = new Tree<Employee>(new Employee { Id = 1, FirstName = "Janet", LastName = "Gates", Department = "IT" }); empTree.Insert(new Employee { Id = 2, FirstName = "O", LastName = "G", Department = "Marketing" }); empTree.Insert(new Employee { Id = 4, FirstName = "K", LastName = "H", Department = "IT" }); empTree.Insert(new Employee { Id = 6, FirstName = "L", LastName = "H", Department = "Sales" }); empTree.Insert(new Employee { Id = 3, FirstName = "E", LastName = "L", Department = "Sales" }); empTree.Insert(new Employee { Id = 5, FirstName = "D", LastName = "L", Department = "Marketing" }); var depts = empTree.Select(d => d.Department).Distinct(); foreach (var dept in depts) Console.WriteLine("Department: {0}", dept); } }