Are elements in a .NET's Dictionary sequential? [duplicate]

Question

Say, if I create a dictionary like this:

Dictionary<string, MyClass> dic = new Dictionary<string, MyClass>();

dic.add("z1", val1);
dic.add("abc9", val2);
dic.add("abc8", val3);
dic.add("ABC1", val4);

So when I do:

foreach (KeyValuePair<string, MyClass> kvp in dic)
{
}

Am I guaranteed to have these values retrieved as such: "z1", "abc9", "abc8", "ABC1"?

And what if I first do this, will it be: "z1", "abc8", "ABC1"?

dic.Remove("abc9");

Answer 1

No. From MSDN (emphasis mine)

For purposes of enumeration, each item in the dictionary is treated as a KeyValuePair<TKey, TValue> structure representing a value and its key. The order in which the items are returned is undefined.

You may want to look at the OrderedDictionary class if you want more control over the iteration order.

Answer 2

The short answer is No. Order is not guaranteed in a Dictionary<TKey, TValue>, nor should you count on order being maintained.

You might want to check into OrderedDictionary instead.

Example:

OrderedDictionary d = new OrderedDictionary();

d.Add("01", "First");
d.Add("02", "Second");
d.Add("03", "Third");
d.Add("04", "Fourth");
d.Add("05", "Fifth");

for(int i = 0; i < d.Count; i++) // Print values in order
{
   Console.WriteLine(d[i]);
}

Note there's no generic OrderedDictionary<TKey,TValue> version for some odd reason. However, this question has some hints on how to implement one.