Web Api adding underscore prefix to json property names

Question

This is what I get

{"_ProviderId":476,"_FirstName":" ","_LastName":"Nam Of Provders","_Specialty":"Pediatrics"}

api code

Public Class ProviderSimpleModel
    Public Property ProviderId As Integer
    Public Property FirstName As String
    Public Property LastName As String
    Public Property Specialty As String
    Public ReadOnly Property Name() As String
        Get
            Return If(FirstName, "").Trim() + " " + If(LastName, "").Trim()
        End Get

    End Property
End Class
<HttpGet>
Public Function GetProviderSimpleList(Optional id As Integer = 0) As List(Of ProviderSimpleModel)
    Dim db As New LinqConsole.MyDataContext

    Dim q = From pr In db.Providers
            Where pr.ProviderId = id OrElse id = 0
            Select New ProviderSimpleModel With
            {
                .ProviderId = pr.ProviderId,
                .FirstName = pr.FirstName,
                .LastName = pr.LastName,
                .Specialty = pr.Specialty
            }

    Dim list = q.OrderBy(Function(x) x.FirstName).ThenBy(Function(x) x.LastName).ToList()
    db.Dispose()
    Return list


End Function

why is this happening and how to stop it?

Answer 1

Updated Newtonsoft from 10.x to 13.x, issue solved.