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Working with Dictionary Collections

Another very useful generic collection is the Dictionary, which works with key/value pairs. There is a non-generic collection, called a Hashtable that does the same thing, except that it operates on type object. However, as explained earlier in this lesson, you want to avoid the non-generic collections and use thier generic counterparts instead. The scenario I'll use for this example is that you have a list of Customers that you need to work with. It would be natural to keep track of these Customers via their CustomerID. The Dictionary example will work with instances of the following Customer class:

public class Customer
{
public Customer(int id, string name)
{
ID = id;
Name = name;
}

private int m_id;

public int ID
{
get { return m_id; }
set { m_id = value; }
}

private string m_name;

public string Name
{
get { return m_name; }
set { m_name = value; }
}
}

The Customer class above has a constructor to make it easier to initialize. It also exposes it's state via public properties. It isn't very sophisticated at this point, but that's okay because its only purpose is to help you learn how to use a Dictionary collection. The following example populates a Dictionary collection with Customer objects and then shows you how to extract entries from the Dictionary:

Dictionary customers = new Dictionary();

Customer cust1 = new Customer(1, "Cust 1");
Customer cust2 = new Customer(2, "Cust 2");
Customer cust3 = new Customer(3, "Cust 3");

customers.Add(cust1.ID, cust1);
customers.Add(cust2.ID, cust2);
customers.Add(cust3.ID, cust3);

foreach (KeyValuePair custKeyVal in customers)
{
Console.WriteLine(
"Customer ID: {0}, Name: {1}",
custKeyVal.Key,
custKeyVal.Value.Name);
}