Shared Dictionary. Suppose we have some data that is useful throughout our VB.NET program, not just one class. And it can be stored within a Dictionary—a Shared Dictionary is ideal here.

Dictionary

With this construct, we can designate a Dictionary as a global store of key-value pairs. We can add, loop over, test and remove keys from the Shared Dictionary.

Shared

Example. We introduce a class named Example, and inside the Example class we have a Shared Dictionary "gems." This Dictionary stores String keys and Integer values among all Example instances.

Dictionary GetValueOrDefault

Class Example
    Public Shared Dim gems As Dictionary(Of String, Integer) = New Dictionary(Of String, Integer)

    Shared Sub Test()
        ' Use GetValueOrDefault to find a value.
        Dim value As Integer = gems.GetValueOrDefault("diamond")
        Console.WriteLine($"SHARED DICTIONARY RESULT: {value}")
    End Sub

    Shared Sub PrintAll()
        ' Use For-Each loop to enumerate entries in the Dictionary.
        For Each pair in gems
            Console.WriteLine($"PAIR: {pair}")
        Next
    End Sub
End Class

Module Module1
    Sub Main()
        ' Step 1: add 2 entries to the Shared Dictionary.
        Example.gems.Add("diamond", 500)
        Example.gems.Add("ruby", 200)

        ' Step 2: find a value for a key on the Shared Dictionary.
        Example.Test()

        ' Step 3: print all entries in the Shared Dictionary.
        Example.PrintAll()
    End Sub
End Module
SHARED DICTIONARY RESULT: 500
PAIR: [diamond, 500]
PAIR: [ruby, 200]

Summary. Shared Dictionaries can both reduce memory usage, by eliminating duplicate fields, and simplify programs, by allowing us to unify the Dictionary initialization logic.