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"};
string name =
presidents.Where(n => n.Equals("H")).DefaultIfEmpty("Missing").First(); Console.WriteLine(name);
}
}
Author: coder
Without Using DefaultIfEmpty
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"};
string jones = presidents.Where(n => n.Equals("H")).First();
if (jones != null)
Console.WriteLine("H was found");
else
Console.WriteLine("H was not found");
}
}
Using DefaultIfEmpty in Where clause
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"};
string jones = presidents.Where(n => n.Equals("H")).DefaultIfEmpty().First();
if (jones != null)
Console.WriteLine("H was found.");
else
Console.WriteLine("H was not found.");
}
}
Deferred Query Execution: shows how query execution is deferred until the query is enumerated at a foreach statement.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
public static void Main() {
int[] numbers = new int[] { 5, 4, 1, 3, 9 };
int i = 0;
var q =
from n in numbers
select ++i;
foreach (var v in q) {
Console.WriteLine("v = {0}, i = {1}", v, i);
}
}
}
How queries can be executed immediately with operators such as ToList().
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
public static void Main() {
int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int i = 0;
var q = (
from n in numbers
select ++i)
.ToList();
// The local variable i has already been fully
// incremented before we iterate the results:
foreach (var v in q) {
Console.WriteLine("v = {0}, i = {1}", v, i);
}
}
}
The aggregation operators return a scalar value
using System;
using System.Collections.Generic;
using System.Linq;
public class MainClass {
public static void Main() {
int[] numbers = { 10, 9, 8, 7, 6 };
int count = numbers.Count();
int min = numbers.Min();
}
}
Contains with IEqualityComparer
using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MyStringifiedNumberComparer : IEqualityComparer<string> {
public bool Equals(string x, string y) {
return (Int32.Parse(x) == Int32.Parse(y));
}
public int GetHashCode(string obj) {
return Int32.Parse(obj).ToString().GetHashCode();
}
}
public class MainClass {
public static void Main() {
string[] stringifiedNums = {"001", "49", "017", "0080", "00027", "2" };
bool contains = stringifiedNums.Contains("2",new MyStringifiedNumberComparer());
Console.WriteLine(contains);
}
}