## System Collections
We have 3 collections namespace in C#
- System.Collections
- Store items as Object
- ArrayList
- Queue
- Stack
- Hashtable
- System.Collections.Generic
- Using Generics to specify one data type
- List
- Queue
- Stack
- Dictionary
- System.Collections.Concurrent
- As previous bu thread safe
## Live coding - List
```csharp
namespace Lecture;
public static class Program {
public static void Main() {
var myList = new List();
myList.Add(12);
myList.Add(23);
myList.Add(122);
myList.Add(312);
myList.Add(142);
myList[4] = 1;
int a = myList[5];
Console.WriteLine($"{myList}"); // Will return the type of the list and the value
Console.WriteLine(a); // Will return the value a (myList[5])
foreach (var element in myList) {
Console.WriteLine($"{element}");
} // Will display each element of the list
myList.ForEach(x => Console.WriteLine($"{x}")); // Same thing that foreach bellow
var t = myList.GetRange(3, 2);
t.ForEach(x => Console.WriteLine($"{x}"));
myList.sort();
myList.
}
}
```
## Live coding - Dictionary
```csharp
namespace Lecture;
public static class Program {
public static void Main() {
var dict = Dictionary<
}
}
```