Question

I found an example showing that a dictionary can be initialised as follows:

Dictionary<string, int> d = new Dictionary<string, int>()
{
    {"cat", 2},
    {"dog", 1},
    {"llama", 0},
    {"iguana", -1}
};

I don’t understand how the syntax {"cat", 2} is valid for creating a Key-Value Pair. Collection initialisation syntax seems to be of the form new MyObjType(){}, while anonymous objects are of the form {a="a", b="b"}. What is actually happening here?

Answer 1

Alright lets take a look at the code here:

Dictionary<string, int> d = new Dictionary<string, int>() 
{ 
    {"cat", 2}, 
    {"dog", 1}, 
    {"llama", 0}, 
    {"iguana", -1} 
};

a dictionary holds two things, a key, and a value.
your declaration, Dictionary<string, int>, means the keys are strings, and the values are integers.

now, when your adding an item, for instance {"cat", 2},, the key is cat. this would be equivilent to you doing something like, d.Add("cat", 2);. a dictionary can hold anything, from <string, string> to <customClass, anotherCustomClass>. and to call it up you can use int CAT = d["cat"]; to which the value of int CAT would be 2. an example of this would be:

Dictionary<string, int> dict = new Dictionary<string, int>() 
{ 
    {"cat", 1}
};
dict.Add("dog", 2);
Console.WriteLine("Cat="+dict["cat"].ToString()+", Dog="+dict["dog"].ToString());

in in there, your adding cat and dog with different values and calling them up