What is the difference between Tuple, Dictionary and List in C#?

This question already has an answer here.

I was trying to use Tuple in my application. So I want to differentiate a Tuple, Dictionary and List.

 Dictionary<int, string> dic = new Dictionary<int, string>();
 Tuple<int, string> tuple = new Tuple<int, string>();
 List<int> list = new List<int>();

What is the difference between these three?

First, AFAIK, there isn't any list that takes two type parameters - so your List could either be a List<int> or List<string> (or a SortedList<int,string>, but that's a different class).

A Tuple<T1, T2> holds two values - one int and one string in this case. You can use a Tuple to bind together items (that might be of different types). This may be useful in many situations, like, for instance, you want to return more than one value from a method.

I personally hate the Item1, Item2 property names, so I would probably use a wrapper class around Tuples in my code.

A Dictionary<TKey, TValue> is a collection of KeyValuePair<TKey, TValue>. A Dictionary maps keys to values, so that you can have, for instance, a dictionary of people and for each person have their SSN as a key.

A List<T> is a collection of T. You can get individual items by using the index, the Find method, or simply LINQ (since it implements IEnumerable<T>).

While the answer you have linked discusses the differentiation between List<T> and Dictionary<int, T>, Tuple<int, string> is not addressed.

From MSDN

Represents a 2-tuple, or pair.

A tuple is a pair of values, opposed to the other types, which represent sort of collections. Think of a method, which returns an error code and string for the last error (I would not write the code this way, but to get the idea)

Tuple<int, string> GetLastError()
{
    ...
}

Now you can use it like

var lastError = GetLastError();
Console.WriteLine($"Errorcode: {lastError.Item1}, Message: {lastError.Item2}");

This way you do not have to create a class, if you want to return a compound value.

Please Note: As of C# 7 there is a newer, more concise syntax for returning tuples.

A list can store a sequence of objects in a certain order such that you can index into the list, or iterate over the list. List is a mutable type meaning that lists can be modified after they have been created.

A tuple is similar to a list except it is immutable. There is also a semantic difference between a list and a tuple. To quote Nikow's answer:

Tuples have structure, lists have order.

A dictionary is a key-value store. It is not ordered and it requires that the keys are hashable. It is fast for lookups by key.