Json conversion to double and bind to WPF nummericupdown fails - json

Question

Currently i get an error on a binding. The situation is that i write my settings to a JSON file. When the app opens again the JSON file is read and used throughout the application. Now there's a strange thing: When i bind a double value to the value of a nummericupdown than i get an error: type 'JValue' to type 'System.Nullable1[System.Double]'for 'en-US' however this error doesn't occur when i recreate the JSON list and file. (simply said when i delete the file and restart the app it will create a new instance of a class en write it to disk)
Property in class:
Public Property SomeValue As Double
Write/Reader JSON:
'Write
Using _file As StreamWriter = New StreamWriter(SettingFilePath)
Dim serializer As New JsonSerializer()
serializer.Formatting = Formatting.Indented
serializer.Serialize(_file, Me)
End Using
'Read
Return JsonConvert.DeserializeObject(Of Settings)(File.ReadAllText(settingsfile))
JSON string:
"SomeValue": 1.0,
Binding in XAML:
<Controls:NumericUpDown
Width="200"
HorizontalAlignment="Center"
Maximum="5"
Minimum="1"
NumericInputMode="All"
Speedup="false"
Value="{Binding SomeValue}" />
Please note that i use the Mathapps Metro nummericupdown control version 1.6.5
Newtonsoft version 10.0.0.1 (Cannot update due to dependencies)
Edit:
As asked i digged deeper and now know where it starts, but don't know yet how to resolve it. Is start with my class for example:
Public class Hello
Dim a as Object
Dim b as EnumTypeOfObjectIn_A
Dim SomeOtherStuff as String
End class
Now when i DeserializeObject de file to the Class Hello then variable a becomes a object of type JObject and this is why alot of logica afterwords goes wrong. When i create the object in code everything goes well because the TypeOf object matches the one i put in. So is there a work arround for the Deserializer to convert the object to the one that is indicated in variable b ?

Answer 1

Found the solution i was looking for. The Newtonsoft JSON contains the JsonSerializerSettings class that helps the de/serialization process. For me it is important to add the Type of object when serializing so that's exactly what TypeNameHandling and TypeNameAssemblyFormatHandling is for in the Newtonsoft JSON assembly
I ended up with this code:
Public Class Hello
Public Property A As Object
Dim settingsfile As String = "C:\jsontest.json"
Public Sub Save()
Using _file As StreamWriter = New StreamWriter(settingsfile)
_file.Write(JsonConvert.SerializeObject(Me, Formatting.Indented, New JsonSerializerSettings() With {
.TypeNameHandling = TypeNameHandling.Objects,
.TypeNameAssemblyFormatHandling = TypeNameAssemblyFormatHandling.Simple
}))
End Using
End Sub
Public Function Load() As Hello
Return JsonConvert.DeserializeObject(Of Hello)(File.ReadAllText(settingsfile), New JsonSerializerSettings() With {.TypeNameHandling = TypeNameHandling.Objects})
End Function
End Class
Public Class Person
Public Property Name As String
Public Property Age As Integer
Sub New()
Me.Name = "John"
Me.Age = 130
End Sub
End Class
Producing this JSON output, note the $Type
{
"$type": "MyNamespace.Hello, MyNamespace",
"A": {
"$type": "MyNamespace.Person, MyNamespace",
"Name": "John",
"Age": 130
}
}