I think, the differences between ArrayList and List<T> are:
List<T>, where T is value-type is faster than ArrayList. This is
because List<T> avoids boxing/unboxing (where T is value-type).ArrayList used just for backward
compatibility. (is not a real difference, but i think it is
important note).ArrayList then List<T>ArrayList has IsSynchronized property. So, It is easy
to create and use syncronised ArrayList. I didin't found IsSynchronized property for List<T>. Also Keep in mind this type of synchronization is relatively inefficient, msdn):
var arraylist = new ArrayList();
var arrayListSyncronized = ArrayList.Synchronized(arraylist
Console.WriteLine($"syncronized {arraylist.IsSynchronized}");
Console.WriteLine($"syncronized {arrayListSyncronized.IsSynchronized}");
var list = new List<object>();
var listSyncronized = ArrayList.Synchronized(list);
Console.WriteLine($"syncronized {list.IsSynchronized}");//error, no such prop
Console.WriteLine($"syncronized {list.IsSynchronized}");//error, no such prop
ArrayList has ArrayList.SyncRoot property which can be used for syncronisation (msdn). List<T> hasn't SyncRoot property, so in
the following construction you need to use some object if you use List<T>:
ArrayList myCollection = new ArrayList();
lock(myCollection.SyncRoot) // ofcourse you can use another object for this goal
{
foreach (object item in myCollection)
{
// ...
}
}