C# - Collections
Collection Summary
Name: List<T>
Strength: A growing array
Name: Queue<T>, Stack<T>
Strength: For FIFO and LIFO
Name: HashSet<T>
Strength: Unique items only
Name: LinkedList<T>
Strength: Flexible inserts
Name: Dictionary<Tkey, Tvalue>
Strength: Quick look up by key
Name: SortedSet<T>, SortedList<Tkey, Tvalue>, SortedDictionary<Tkey, Tvalue>
Strength: Sorted & unique, Sorted & memory efficent, Sorted, fast insert and removals
List<T> Example
List<Employee> employee = new List<Employee>();
employee.Add(new Employee { Name = "John" });
employee.Add(new Employee { Name = "Alex" });
LinkedList<T> Example
LinkedList<int> links = new LinkedList<int>();
links.AddFirst(2);
links.AddFirst(3);
var first = links.First;
links.AddBefore(first, 5);
foreach (var link in links)
{
Console.WriteLine(link); // output: 5 3 2
}
Queue<T>
// FIFO data structure
Queue<Employee> line = new Queue<Employee>();
line.Enqueue(new Employee { Name = "A" });
line.Enqueue(new Employee { Name = "B" });
line.Enqueue(new Employee { Name = "C" });
while (line.Count > 0)
{
var employee = line.Dequeue();
Console.WriteLine(employee.Name); // output: A B C
}
Stack<T> Example
// LIFO data structure
Stack<Employee> stack = new Stack<Employee>();
stack.Push(new Employee { Name = "A" });
stack.Push(new Employee { Name = "B" });
stack.Push(new Employee { Name = "C" });
while (stack.Count > 0)
{
var employee = stack.Pop();
Console.WriteLine(employee.Name); // output: C B A
}
Dictionary<Tkey, Tvalue> Example
var dict = new Dictionary<string, Employee>();
dict.Add("A", new Employee { Name = "A" });
dict.Add("B", new Employee { Name = "B" });
dict.Add("C", new Employee { Name = "C" });
foreach (var item in dict)
{
// output: A : A, B : B, C : C
Console.WriteLine("{0} : {1}", item.Key, item.Value.Name);
}
Dictionary<Tkey, Tvalue> Example #2
var dict = new Dictionary<string List<Employee>>();
dict.Add("Sales", new List<Employee>
{
new Employee { Name = "A" },
new Employee { Name = "B" },
new Employee { Name = "C" }
});
dict["Engineering"].Add(new Employee { Name = "D" });
foreach (var department in dict)
{
foreach (var item in department.Value)
{
Console.WriteLine(item.Name); // output: A B C D
}
}
SortedDictionary<Tkey, Tvalue> Example
var sortedDict = new SortedDictionary<string, List<Employee>>();
sortedDict.Add("Sales", new List<Employee>
{
new Employee {Name = "Tom"},
new Employee {Name = "Jerry"},
new Employee {Name = "Heather"}
});
sortedDict.Add("Enginnering", new List<Employee>
{
new Employee {Name = "Vic"},
new Employee {Name = "Chris"}
});
foreach (var dep in sortedDict)
{
// output 1: The count for Engineering is 2
// output 2: The count for Sales is 3
Console.WriteLine("The count for {0} is {1}", dep.Key, dep.Value.Count);
}