Visual Basic 2012 Programmer's Reference

COLLECTION INITIALIZERS

Initializers allow you to easily initialize collection classes that have an Add method. To initialize a collection, follow the variable’s instantiation with the keyword From and then a series of comma-separated values inside braces.

For example, the following code snippet initializes an ArrayList, StringCollection, and generic List(Of Person). Notice how the generic List’s initializer includes a series of new Person objects that are initialized with the With keyword.

Dim numbers As New ArrayList() From {1, 2, 3}
Dim names As New StringCollection() From {"Alice", "Bob", "Cynthia"}
Dim authors As New List(Of Person) From {
    New Person() With {.FirstName = "Simon", .LastName = "Green"},
    New Person() With {.FirstName = "Christopher", .LastName = "Moore"},
    New Person() With {.FirstName = "Terry", .LastName = "Pratchett"}
}

If a collection’s Add method takes more than one parameter, simply include the appropriate values for each item inside their own sets of braces. The following code uses this method to initialize a NameValueCollection and a Dictionary with Integer keys and String values:

Dim phone_numbers As New NameValueCollection() From {
    {"Ashley", "502-253-3748"},
    {"Jane", "505-847-2984"},
    {"Mike", "505-847-3984"},
    {"Shebly", "502-487-4939"}
}
Dim greetings As New Dictionary(Of Integer, String) From {
    {1, "Hi"},
    {2, "Hello"},
    {3, "Holla"}
}

The same technique works for other collections that need two values such as ListDictionary, Hashtable, HybridDictionary, ...