Csharp/C Sharp/LINQ/Query
Содержание
- 1 All employees in a tree are grouped by department
- 2 Chaining Query Operators/extracts all strings containing the letter "a", sorts them by length, and then converts the results to uppercase
- 3 Get Distinct departments with condition
- 4 Use Contains, Length and ToUpper from Linq
- 5 Use from where select to choose the Employees in the IT department from a tree
- 6 Use LINQ to get Employees in the IT department from a tree
- 7 Use select to retrieve all nodes in a Binary tree
All employees in a tree are grouped by department
<source lang="csharp"> 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.rupareTo(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>.rupareTo(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("\t{0} {1}", emp.FirstName, emp.LastName);
}
}
}
}
</source>
Chaining Query Operators/extracts all strings containing the letter "a", sorts them by length, and then converts the results to uppercase
<source lang="csharp"> using System; using System.Collections.Generic; using System.Linq; class LinqDemo {
static void Main() {
string[] names = { "J", "P", "G", "P" };
IEnumerable<string> query = names
.Where(n => n.Contains("a"))
.OrderBy(n => n.Length)
.Select(n => n.ToUpper());
foreach (string name in query) Console.Write(name + "|");
}
}
</source>
Get Distinct departments with condition
<source lang="csharp"> 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.rupareTo(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>.rupareTo(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);
}
}
</source>
Use Contains, Length and ToUpper from Linq
<source lang="csharp"> using System; using System.Collections.Generic; using System.Linq; public class MainClass {
public static void Main() {
string[] names = { "Tom", "Dick", "Harry", "Mary", "Jay" };
IEnumerable<string> filtered = names.Where(n => n.Contains("a"));
IEnumerable<string> sorted = filtered.OrderBy(n => n.Length);
IEnumerable<string> finalQuery = sorted.Select(n => n.ToUpper());
foreach (string name in filtered)
Console.Write(name + "|");
Console.WriteLine();
foreach (string name in sorted)
Console.Write(name + "|");
Console.WriteLine();
foreach (string name in finalQuery)
Console.Write(name + "|");
}
}
</source>
Use from where select to choose the Employees in the IT department from a tree
<source lang="csharp"> 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.rupareTo(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>.rupareTo(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);
}
}
</source>
Use LINQ to get Employees in the IT department from a tree
<source lang="csharp"> 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.rupareTo(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>.rupareTo(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);
}
}
</source>
Use select to retrieve all nodes in a Binary tree
<source lang="csharp"> 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.rupareTo(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>.rupareTo(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 allEmployees = from e in empTree.ToList<Employee>()
select e;
foreach (var emp in allEmployees)
Console.WriteLine(emp);
}
}
</source>
