Dictionaries are a data structure where a key/value pairs are stored. There are some rules for dictionaries:
Keys in dictionaries must be unique. You cannot have duplicate keys. You can have duplicate values.
Keys cannot be null. Values can be null.
Only elements of the same type can be stored in a dictionary.
A dictionary’s capacity depends on how many elements a dictionary has the capability of holding.
Structure of a dictionary
The structure of a dictionary is as follows:
Creating a dictionary
In order to create a dictionary, we first need to import the appropriate namespace:
Let’s say we want to create a dictionary that has keys of type
int and values of type
string. This is how we do it:
Dictionary<int,string> users = new Dictionary<int,string>(); //Shorthand var users = new Dictionary<int,string>();
Inserting data into a dictionary
In order to insert data into a dictionary, we use the
users.Add(1, "Sys Admin"); users.Add(2, "Network Admin"); users.Add(3, "grahamb"); users.Add(4, "petersonj");
Checking for a key in a dictionary
If we want to find if a particular key is in a dictionary, we use the
Checking for a value in a dictionary
If on the other hand, we want to find a value, we use the
Removing data from a dictionary
In order to remove data from a dictionary, we use the
Remove method along with the key:
Clearing a dictionary
If we want to clear the entire dictionary, we use the