Csharp/C Sharp/LINQ/Distinct
Содержание
Distinct 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 = {"Grant", "Harding", "Harrison", "Hayes", "Hoover", "Jackson"};
Console.WriteLine("presidents count: " + presidents.Count());
IEnumerable<string> presidentsWithDupes = presidents.Concat(presidents);
Console.WriteLine("presidentsWithDupes count: " + presidentsWithDupes.Count());
IEnumerable<string> presidentsDistinct = presidentsWithDupes.Distinct();
Console.WriteLine("presidentsDistinct count: " + presidentsDistinct.Count());
}
}
</source>
Get Distinct departments
<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 = (from d in empTree select d.Department).Distinct();
foreach (var dept in depts)
Console.WriteLine("Department: {0}", dept);
}
}
</source>
prints the unique Category names
<source lang="csharp"> using System; using System.Collections.Generic; using System.Linq; using System.Text; public class MainClass {
public static void Main() {
List<Product> products = GetProductList(); var categoryNames = (
from p in products
select p.Category)
.Distinct();
Console.WriteLine("Category names:");
foreach (var n in categoryNames) {
Console.WriteLine(n);
}
}
static List<Product> GetProductList() {
List<Product> empTree = new List<Product>();
empTree.Add(new Product { ProductName = "A", Category = "O", UnitPrice = 12, UnitsInStock = 5, Total = 36, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = "B", Category = "O", UnitPrice = 2, UnitsInStock = 4, Total = 35, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = "C", Category = "O", UnitPrice = 112, UnitsInStock = 3, Total = 34, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = "D", Category = "O", UnitPrice = 112, UnitsInStock = 0, Total = 33, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = "E", Category = "O", UnitPrice = 1112, UnitsInStock = 2, Total = 32, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = "F", Category = "O", UnitPrice = 11112, UnitsInStock = 0, Total = 31, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
return empTree;
}
} class Product : IComparable<Product> {
public string ProductName { get; set; }
public string Category { get; set; }
public int UnitPrice { get; set; }
public int UnitsInStock { get; set; }
public int Total { get; set; }
public DateTime OrderDate { get; set; }
public int Id { get; set; }
public override string ToString() {
return String.Format("Id: {0}, Name: {1} , Category: {3}", this.Id, this.ProductName, this.Category);
}
int IComparable<Product>.rupareTo(Product other) {
if (other == null)
return 1;
if (this.Id > other.Id)
return 1;
if (this.Id < other.Id)
return -1;
return 0;
}
}
</source>
Set Operators: Distinct
<source lang="csharp"> using System; using System.Collections.Generic; using System.Linq; using System.Text; public class MainClass {
public static void Main() {
int[] fl = { 2, 2, 3, 5, 5 };
var uniqueFactors = fl.Distinct();
Console.WriteLine("Prime factors of 300:");
foreach (var f in uniqueFactors) {
Console.WriteLine(f);
}
}
}
</source>
Use Linq Distinct to get the distinct value in an array
<source lang="csharp"> using System; using System.Collections; using System.Collections.Generic; using System.Text; using System.Linq; public class MainClass{
public static void Main(){
int[] numbers = {1, 1, 2, 3, 3};
Console.Write(numbers.Distinct());
}
}
</source>
