var numbers1to5 = new[] {1, 2, 3, 4, 5};
var numbers4to8 = new[] {4, 5, 6, 7, 8};
var numbers1to8 = numbers1to5.Concat(numbers4to8);
Console.WriteLine(string.Join(",", numbers1to8));
//1,2,3,4,5,4,5,6,7,8
Note that duplicates are kept in the result. If this is undesirable, use...
var numbers = new[] {1,2,3,4,5};
var firstNumber = numbers.First();
Console.WriteLine(firstNumber); //1
var firstEvenNumber = numbers.First(n => (n & 1) == 0);
Console.WriteLine(firstEvenNumber); //2
The following throws InvalidOperationException with message "Sequence contain...
var oneNumber = new[] {5};
var theOnlyNumber = oneNumber.Single();
Console.WriteLine(theOnlyNumber); //5
var numbers = new[] {1,2,3,4,5};
var theOnlyNumberSmallerThanTwo = numbers.Single(n => n < 2);
Console.WriteLine(theOnlyNumberSmallerThanTwo); //1
The following throws Invalid...
var numbers = new[] {1,2,3,4,5};
var lastNumber = numbers.Last();
Console.WriteLine(lastNumber); //5
var lastEvenNumber = numbers.Last(n => (n & 1) == 0);
Console.WriteLine(lastEvenNumber); //4
The following throws InvalidOperationException:
var lastNegativeNumber = numbers.Last(n...
var oneNumber = new[] {5};
var theOnlyNumber = oneNumber.SingleOrDefault();
Console.WriteLine(theOnlyNumber); //5
var numbers = new[] {1,2,3,4,5};
var theOnlyNumberSmallerThanTwo = numbers.SingleOrDefault(n => n < 2);
Console.WriteLine(theOnlyNumberSmallerThanTwo); //1
var theOnl...
Returns true if the collection has any elements that meets the condition in the lambda expression:
var numbers = new[] {1,2,3,4,5};
var isNotEmpty = numbers.Any();
Console.WriteLine(isNotEmpty); //True
var anyNumberIsOne = numbers.Any(n => n == 1);
Console.WriteLine(anyNumberIsOne); //Tr...
var numbers = new[] {1,2,3,4,5};
var allNumbersAreOdd = numbers.All(n => (n & 1) == 1);
Console.WriteLine(allNumbersAreOdd); //False
var allNumbersArePositive = numbers.All(n => n > 0);
Console.WriteLine(allNumbersArePositive); //True
Note that the All method functions by che...
For classes, interfaces, delegate, array, nullable (such as int?) and pointer types, default(TheType) returns null:
class MyClass {}
Debug.Assert(default(MyClass) == null);
Debug.Assert(default(string) == null);
For structs and enums, default(TheType) returns the same as new TheType():
struct...
The readonly keyword is a field modifier. When a field declaration includes a readonly modifier, assignments to that field can only occur as part of the declaration or in a constructor in the same class.
The readonly keyword is different from the const keyword. A const field can only be initialized...
Enumerable.Select returns an output element for every input element.
Whereas Enumerable.SelectMany produces a variable number of output elements for each input element. This means that the output sequence may contain more or fewer elements than were in the input sequence.
Lambda expressions passe...
Skip will enumerate the first N items without returning them.
Once item number N+1 is reached, Skip starts returning every enumerated item:
var numbers = new[] {1,2,3,4,5};
var allNumbersExceptFirstTwo = numbers.Skip(2);
Console.WriteLine(string.Join(",", allNumbersExceptFirstTwo.ToA...
This method takes the first n elements from an enumerable.
var numbers = new[] {1,2,3,4,5};
var threeFirstNumbers = numbers.Take(3);
Console.WriteLine(string.Join(",", threeFirstNumbers.ToArray()));
//1,2,3
var numbers = new[] {1,2,3,4,5};
var sameNumbers = new[] {1,2,3,4,5};
var sameNumbersInDifferentOrder = new[] {5,1,4,2,3};
var equalIfSameOrder = numbers.SequenceEqual(sameNumbers);
Console.WriteLine(equalIfSameOrder); //True
var equalIfDifferentOrder = numbers.SequenceEqual(sameNumbersInDi...
var mixed = new object[] {1,"Foo",2,"Bar",3,"Fizz",4,"Buzz"};
var numbers = mixed.OfType<int>();
Console.WriteLine(string.Join(",", numbers.ToArray()));
//1,2,3,4
