Imports System
Imports System.Text.Json
Imports System.Text.Json.Serialization

' We'll use these two classes to demonstrate encoding and
' decoding of custom types below.
Public Class Response1
    Public Property Page As Integer
    Public Property Fruits As String()
End Class

' Only public properties will be serialized/deserialized in JSON.
' We can use attributes to customize the JSON property names.
Public Class Response2
    <JsonPropertyName("page")>
    Public Property Page As Integer

    <JsonPropertyName("fruits")>
    Public Property Fruits As String()
End Class

Module JSONExample
    Sub Main()
        ' First we'll look at encoding basic data types to
        ' JSON strings. Here are some examples for atomic values.
        Console.WriteLine(JsonSerializer.Serialize(True))
        Console.WriteLine(JsonSerializer.Serialize(1))
        Console.WriteLine(JsonSerializer.Serialize(2.34))
        Console.WriteLine(JsonSerializer.Serialize("gopher"))

        ' And here are some for arrays and dictionaries, which encode
        ' to JSON arrays and objects as you'd expect.
        Dim slcD As String() = {"apple", "peach", "pear"}
        Console.WriteLine(JsonSerializer.Serialize(slcD))

        Dim mapD As New Dictionary(Of String, Integer) From {
            {"apple", 5},
            {"lettuce", 7}
        }
        Console.WriteLine(JsonSerializer.Serialize(mapD))

        ' The JSON package can automatically encode your
        ' custom data types.
        Dim res1D As New Response1 With {
            .Page = 1,
            .Fruits = New String() {"apple", "peach", "pear"}
        }
        Console.WriteLine(JsonSerializer.Serialize(res1D))

        ' You can use attributes on class properties
        ' to customize the encoded JSON property names. Check the
        ' definition of `Response2` above to see an example
        ' of such attributes.
        Dim res2D As New Response2 With {
            .Page = 1,
            .Fruits = New String() {"apple", "peach", "pear"}
        }
        Console.WriteLine(JsonSerializer.Serialize(res2D))

        ' Now let's look at decoding JSON data into .NET
        ' values. Here's an example for a generic data structure.
        Dim jsonString As String = "{""num"":6.13,""strs"":[""a"",""b""]}"

        ' We need to provide a type where the JSON
        ' package can put the decoded data. This
        ' Dictionary(Of String, Object) will hold a dictionary of strings
        ' to arbitrary data types.
        Dim dat As Dictionary(Of String, Object) = 
            JsonSerializer.Deserialize(Of Dictionary(Of String, Object))(jsonString)
        Console.WriteLine(String.Join(", ", dat.Select(Function(kvp) $"{kvp.Key}: {kvp.Value}")))

        ' In order to use the values in the decoded dictionary,
        ' we'll need to convert them to their appropriate type.
        ' For example here we convert the value in `num` to
        ' the expected `Double` type.
        Dim num As Double = Convert.ToDouble(dat("num"))
        Console.WriteLine(num)

        ' Accessing nested data requires a series of conversions.
        Dim strs As Object() = CType(dat("strs"), Object())
        Dim str1 As String = CStr(strs(0))
        Console.WriteLine(str1)

        ' We can also decode JSON into custom data types.
        ' This has the advantages of adding additional
        ' type-safety to our programs and eliminating the
        ' need for type conversions when accessing the decoded data.
        Dim str As String = "{""page"": 1, ""fruits"": [""apple"", ""peach""]}"
        Dim res As Response2 = JsonSerializer.Deserialize(Of Response2)(str)
        Console.WriteLine($"Page: {res.Page}, Fruits: {String.Join(", ", res.Fruits)}")
        Console.WriteLine(res.Fruits(0))

        ' In the examples above we always used strings as
        ' intermediates between the data and JSON representation.
        ' We can also stream JSON encodings directly to TextWriter
        ' objects like Console.Out.
        Dim d As New Dictionary(Of String, Integer) From {
            {"apple", 5},
            {"lettuce", 7}
        }
        JsonSerializer.Serialize(Console.Out, d)
    End Sub
End Module