System.Collections.Generic.List

Added in .NET 2.0
Represents a collection of objects that can be individually accessed by an index
Appending elements is fast but inserting elements at a given position is slow
Searching using binary search is fast if the list has already been sorted.
This type of collection represents a collection on keys and values
provides access by index numbers

System.Collections.Generic.List 

Fixed Size

Allows modification of elements but does not allow the addition or removal of elements.

myList = new System.Collections.Generic.List<string>(3); 
myList.Add("one"); 
myList.Add("two"); 
myList.Add("three"); 
System.Diagnostics.Debug.Print System.String.Format("Count={0}", myList.Count) 

System.Diagnostics.Debug.Print myList[2]; 

Variable Size

Allows addition, removal and modification of elements.

Where

GenericList.Add = how to check of its already been added ? 

Distinct

GenericList.Distinct.ToList 

ToArray

copy the list to an array

get a value at a given index
get a subrange/sublist between 2 index positions

reverse the order of the items

get an enumerator for the list

Declaring

Items - Add / Remove

Add

System.Collections.Generic.List<string> myList; 
myList = new System.Collections.Generic.List<string>(3); 

myList.Add("one"); 
myList.Add("two"); 
myList.Add("three"); 
myList.Add "four"; 

myList.Add(new object[] {"text",50,False)}; 

AddRange

add multiple elements

System.Collections.Generic.List<string> myList; 
myList = new System.Collections.Generic.List<string>(3); 
string sConCat; 

sConCat = "one;two;three" 
myList.AddRange(sConCat.Split(Ctype(";", Char))) 

Insert a single element

Insert multiple elements

InsertRange

System.Collections.Generic.List<string> moreItems; 
moreItems = new System.Collections.Generic.List<string>(4); 

for (int i=0; i<moreItems.Count; i++) 
{ 
   moreItems[i] = 200; 
} 
myList.InsertRange(2, moreItems); 

Removing

remove a single element

myList.Remove("two"); 

remove all elements based on a matching predicate

remove all

myList.Clear(); 

Items - Updating

Items - Finding

Exists

System.Collections.Generic.List<int> mylist; 
mylist = new System.Collections.Generic.List<int>(); 
mylist.Add(10); 
mylist.Add(20); 
if (mylist.Exists(x => x == 20) == false) 
{ 
} 

First

If you try and use First when there are no values, an exception will be thrown

FirstOrDefault

If you try and use FirstOrDefault when there are no values, the default value will be returned instead of an exception

How to quickly find a particular item anything equivalent to a Dictionary - ContainsKey ?

Looping

foreach (string myText in myList) 
{ 
   System.Console.WriteLine(myText); 
} 

Sorting

Sort (System.Comparison<T> comparison)

Sorts the elements in a list by making use of the System.Comparison<T> delegate

public delegate int Comparison <in T>(T x, T y) 

This delegate must return a signed integer that indicates if
-1 - if x is less than y
1 - if y is less than x
0 - if x equals y

System.Collections.Generic.List<string> mylist; 
mylist = new System.Collections.Generic.List<string>(); 
mylist.Add("hhh"); 
mylist.Add("bbb"); 
mylist.Add(""); 
mylist.Add(null); 
mylist.Add("aaa"); 
mylist.Add("kkk"); 
mylist.Sort(CompareMyItems); 

private static int CompareMyItems(string x, string y) 
{ 
   if (x==null) 
   { 
      if (y==null) { return 0; }   //both null 
      else { return 1; }    //y > null 
   } 
   else 
   { 
      if (y==null) { return 1; }   //x > null 
      else 
      { 
         int retval = x.Length.CompareTo(y.Length); 
         if (retval==0) { return x.CompareTo(y); 
         else { return retval; } 
      } 
   } 
} 

System.Collections.Generic.IList<T>

Added in .NET 2.0
The standard interface for indexable collections
It supports all the methods of ICollection<T> and IEnumerable<T>
get the value of set the value at any position (index value)
find the index of a particular value
Insert at a particular index position
Remove an item at a particular index position

public interface IList<T> : ICollection<T>, IEnumerable<T>, IEnumerable 

This is the common interface for indexable collections
This contains all the methods of ICollection<T> and IEnumerable<T>
You can get the value (or set the value) at any given position
You can find the index of a specific item
You can insert an item at any position
You can remove an item from any position