Sort Dictionary

A Dictionary cannot be sorted—but its keys can be arranged. We can loop over the string keys in alphabetical order.

Some steps are involved in sorting a Dictionary. We obtain the Keys and sort them—and then loop over that. Values from the Dictionary can still be accessed.

Input and output

Consider a VB.NET Dictionary that contains string keys, and integer values. When sorted, we want the keys to be alphabetical.

car 2
zebra 0
apple 1

SORTED:
apple 1
car 2
zebra 0

Example

Let us look at a VB.NET program that adds key and value pairs to a Dictionary. Then, we acquire the list of strings, using the ToList extension method on the Keys property.

Module Module1

    Sub Main()
        ' Create Dictionary with string keys.
        Dim dict As New Dictionary(Of String, Integer)
        dict.Add("car", 2)
        dict.Add("zebra", 0)
        dict.Add("apple", 1)

        ' Get list of keys.
        Dim keys As List(Of String) = dict.Keys.ToList

        ' Sort the keys.
        keys.Sort()

        ' Loop over the sorted keys.
        For Each str As String In keys
            Console.WriteLine("{0} = {1}", str, dict.Item(str))
        Next
    End Sub

End Module
apple = 1
car = 2
zebra = 0

Sort method used

In .NET, the Sort method on the List type is implemented with a Quick Sort algorithm. This means it is efficient on strings.

We sorted the keys in a Dictionary using the Keys property. We then used the ToList and Sort methods to manipulate the elements. Dictionaries themselves cannot be reordered.

Final notes

The collections you can obtain from the Dictionary (such as List) can be sorted. With these resulting types, we can perform many conversions.