Convert Dictionary, String. With a custom VB.NET function, it is possible to convert a Dictionary into a String. And then the String can be persisted to a file.

Though other approaches are possible, such as JSON or binary encoding, the String code here is occasionally useful. It is simple, the output file is human-readable.

Example. This program performs 2 main tasks: it converts a Dictionary to a String, and then a String into a Dictionary. It also stores the data in a text file.

Imports System.IO
Imports System.Text

Module Module1
    Sub Main(args as String())
        ' Step 1: create a Dictionary.
        Dim data = New Dictionary(Of String, Integer)()
        data.Add("bird", 2)
        data.Add("frog", 1)
        data.Add("dog", 20)
        data.Add("rabbit", 3)

        ' Step 2: convert Dictionary to string and write it to the disk.
        Dim line = GetLine(data)
        File.WriteAllText("dict.txt", line)

        ' Step 3: convert string from file into Dictionary and loop over it.
        Dim result = GetDict("dict.txt")
        For Each pair in result
            Console.WriteLine($"PAIR: {pair}")
        Next        
    End Sub

    Function GetLine(data As Dictionary(Of String, Integer)) As String
        ' Use StringBuilder to create a string containing pairs.
        Dim builder = New StringBuilder()
        For Each pair in data
            builder.Append(pair.Key).Append( ":").Append(pair.Value).Append(",")
        Next
        ' Remove end comma.
        Dim result = builder.ToString()
        result = result.TrimEnd(","c)
        Return result
    End Function

    Function GetDict(path As String) As Dictionary(Of String, Integer)
        ' Read in file, and Split it.
        Dim result = New Dictionary(Of String, Integer)()
        Dim value = File.ReadAllText(path)
        Dim tokens = value.Split(New Char() { ":"c, ","c }, StringSplitOptions.RemoveEmptyEntries)
        For i = 0 To tokens.Length - 1
            ' Get name and value from this position, and store it in the Dictionary.
            Dim name = tokens(i)
            Dim freq = tokens(i + 1)
            Dim count = Integer.Parse(freq)
            result(name) = count
            i += 1
        Next
        Return result
    End Function
End Module
PAIR: [bird, 2]
PAIR: [frog, 1]
PAIR: [dog, 20]
PAIR: [rabbit, 3]

Summary. It is possible to generate String data from a Dictionary's contents by looping over it with For Each. Then we can load the file, Split it, and create a Dictionary from it.