How to Initialize a Dictionary in C#

1. Initialize a Dictionary of Pre-Defined data types in C#
2. Initialize a Dictionary of User-Defined data types in C#

In this tutorial, we will discuss methods to initialize a dictionary in C#.

Initialize a Dictionary of Pre-Defined data types in C#

A Dictionary data structure holds data in the form of key/value pairs. The Dictionary<key, value> class can be used to create a dictionary in C#. We can use the constructor of the Dictionary<key, value> class to initialize a dictionary in C#. The following code example shows us how we can initialize a dictionary with the constructor of the Dictionary<key, value> class in C#.

using System;
using System.Collections.Generic;

namespace initialize_dictionary {
  class Program {
    static void Main(string[] args) {
      Dictionary<string, string> myDictionary = new Dictionary<string, string> {
        { "Key1", "Value1" },
        { "Key2", "Value2" },
        { "Key3", "Value3" },
      };
      foreach (var x in myDictionary) {
        Console.WriteLine(x);
      }
    }
  }
}

Output:

[Key1, Value1]
[Key2, Value2]
[Key3, Value3]

We declared and initialized the dictionary myDictionary with the constructor of the Dictionary<key, value> class in C#. We can declare and initialize dictionaries of any pre-defined data type with this example but cannot declare and initialize a dictionary of user-defined data types with this method in C#.

Initialize a Dictionary of User-Defined data types in C#

We can initialize a dictionary of class objects with the new operator in C#. The new operator is used to allocate memory location to the class definition. The following code example shows us how we can initialize a dictionary of class objects with the new operator in C#.

using System;
using System.Collections.Generic;

namespace initialize_dictionary {
  public class Person {
    private string name;
    private string email;
    public Person(string n, string e) {
      name = n;
      email = e;
    }
    class Program {
      static void Main(string[] args) {
        Dictionary<int, Person> myDictionary =
            new Dictionary<int, Person> { { 1, new Person("Person 1", "email1") },
                                          { 2, new Person("Person 2", "email2") },
                                          { 3, new Person("Person 3", "email3") } };
      }
    }
  }

We declared the class Person with the attributes name and email of the string data type. We defined a constructor to initialize the name and email class members. We invoked the constructor of the Person class inside the constructor of the Dictionary<key, value> class with the new operator in C#.