' From: https://github.com/RoyiNamir/SimplePostVariableParameterBindingExtended
' And : http://weblog.west-wind.com/posts/2012/Sep/11/Passing-multiple-simple-POST-Values-to-ASPNET-Web-API
' Add this to Global.asax GlobalConfiguration.Configuration.ParameterBindingRules.Insert(0, SimplePostVariableParameterBinding.HookupParameterBinding)
Imports System.Collections.Generic
Imports System.Collections.Specialized
Imports System.Globalization
Imports System.Linq
Imports System.Net.Http
Imports System.Threading
Imports System.Threading.Tasks
Imports System.Web.Helpers
Imports System.Web.Http.Controllers
Imports System.Web.Http.Metadata
Imports System.Web
Imports Newtonsoft.Json
 
Namespace CC.Net.WebApi
 
    Public Class SimplePostVariableParameterBinding
        Inherits HttpParameterBinding
        Public Const MultipleBodyParameters As String = "MultipleBodyParameters"
        Public Const MultipleBodyParametersRaw As String = "MultipleBodyParametersRaw"
        Public Const AllowJsonContentType As Boolean = True
 
 
        Public Sub New(descriptor As HttpParameterDescriptor)
            MyBase.New(descriptor)
        End Sub
 
        ''' 
        ''' Check for simple binding parameters in POST data. Bind POST
        ''' data as well as query string data
        ''' 
        '''
        '''
        '''
        ''' 
        Public Overrides Function ExecuteBindingAsync(metadataProvider As ModelMetadataProvider, actionContext As HttpActionContext, cancellationToken As CancellationToken) As Task
            Dim stringValue As String = Nothing
 
            Dim col As NameValueCollection = TryReadBody(actionContext.Request)
            If col IsNot Nothing Then
                stringValue = col(Descriptor.ParameterName)
            End If
 
            ' try reading query string if we have no POST/PUT match
            If stringValue Is Nothing Then
                Dim query = actionContext.Request.GetQueryNameValuePairs()
                If query IsNot Nothing Then
                    Dim matches = query.Where(Function(kv) kv.Key.ToLower() = Descriptor.ParameterName.ToLower())
                    Dim keyValuePairs = If(TryCast(matches, IList(Of KeyValuePair(Of String, String))), matches.ToList())
                    If keyValuePairs.Any() Then
                        stringValue = keyValuePairs.First().Value
                    End If
                End If
            End If
 
            Dim value As Object = StringToType(stringValue)
 
            ' Set the binding result here
            SetValue(actionContext, value)
 
            ' now, we can return a completed task with no result
            Dim tcs As New TaskCompletionSource(Of AsyncVoid)()
            tcs.SetResult(Nothing)
            Return tcs.Task
        End Function
 
 
        ''' 
        ''' Method that implements parameter binding hookup to the global configuration object's
        ''' ParameterBindingRules collection delegate.
        ''' 
        ''' This routine filters based on POST/PUT method status and simple parameter
        ''' types.
        ''' 
        '''
        ''' GlobalConfiguration.Configuration.
        '''       .ParameterBindingRules
        '''       .Insert(0,SimplePostVariableParameterBinding.HookupParameterBinding);
        '''    
        '''
        ''' 
        Public Shared Function HookupParameterBinding(descriptor As HttpParameterDescriptor) As HttpParameterBinding
            Dim supportedMethods = descriptor.ActionDescriptor.SupportedHttpMethods
 
            ' Only apply this binder on POST and PUT operations
            If supportedMethods.Contains(HttpMethod.Post) OrElse supportedMethods.Contains(HttpMethod.Put) Then
                Dim supportedTypes = New Type() {GetType(String), GetType(Integer), GetType(System.Nullable(Of Integer)), GetType(Decimal), GetType(System.Nullable(Of Decimal)), GetType(Double), _
                    GetType(System.Nullable(Of Double)), GetType(Long), GetType(System.Nullable(Of Long)), GetType(Boolean), GetType(System.Nullable(Of Boolean)), GetType(DateTime), _
                    GetType(System.Nullable(Of DateTime)), GetType(Byte())}
 
                If supportedTypes.Count(Function(typ) typ = descriptor.ParameterType) > 0 Then
                    Return New SimplePostVariableParameterBinding(descriptor)
                End If
            End If
 
            Return Nothing
        End Function
 
 
        Private Function StringToType(stringValue As String) As Object
            Dim value As Object = Nothing
 
            If stringValue Is Nothing Then
                value = Nothing
            ElseIf Descriptor.ParameterType = GetType(String) Then
                value = stringValue
            ElseIf Descriptor.ParameterType = GetType(Integer) Then
                value = Integer.Parse(stringValue, CultureInfo.CurrentCulture)
 
            ElseIf Descriptor.ParameterType = GetType(System.Nullable(Of Integer)) Then
                value = If(String.IsNullOrWhiteSpace(stringValue), DirectCast(Nothing, System.Nullable(Of Integer)), Integer.Parse(stringValue, CultureInfo.CurrentCulture))
            ElseIf Descriptor.ParameterType = GetType(Long) Then
                value = Long.Parse(stringValue, CultureInfo.CurrentCulture)
            ElseIf Descriptor.ParameterType = GetType(System.Nullable(Of Long)) Then
                value = If(String.IsNullOrWhiteSpace(stringValue), DirectCast(Nothing, System.Nullable(Of Long)), Long.Parse(stringValue, CultureInfo.CurrentCulture))
            ElseIf Descriptor.ParameterType = GetType(Decimal) Then
                value = Decimal.Parse(stringValue, CultureInfo.CurrentCulture)
            ElseIf Descriptor.ParameterType = GetType(System.Nullable(Of Decimal)) Then
                value = If(String.IsNullOrWhiteSpace(stringValue), DirectCast(Nothing, System.Nullable(Of Decimal)), Decimal.Parse(stringValue, CultureInfo.CurrentCulture))
            ElseIf Descriptor.ParameterType = GetType(Double) Then
                value = Double.Parse(stringValue, CultureInfo.CurrentCulture)
            ElseIf Descriptor.ParameterType = GetType(System.Nullable(Of Double)) Then
                value = If(String.IsNullOrWhiteSpace(stringValue), DirectCast(Nothing, System.Nullable(Of Double)), Double.Parse(stringValue, CultureInfo.CurrentCulture))
            ElseIf Descriptor.ParameterType = GetType(DateTime) Then
                value = DateTime.Parse(stringValue, CultureInfo.CurrentCulture)
            ElseIf Descriptor.ParameterType = GetType(System.Nullable(Of DateTime)) Then
                value = If(String.IsNullOrWhiteSpace(stringValue), DirectCast(Nothing, System.Nullable(Of DateTime)), DateTime.Parse(stringValue, CultureInfo.CurrentCulture))
            ElseIf Descriptor.ParameterType = GetType(Boolean) Then
                value = False
                If stringValue = "true" OrElse stringValue = "on" OrElse stringValue = "1" Then
                    value = True
                End If
            ElseIf Descriptor.ParameterType = GetType(System.Nullable(Of Boolean)) Then
                value = False
                If String.IsNullOrWhiteSpace(stringValue) Then
                    value = DirectCast(Nothing, System.Nullable(Of Boolean))
                ElseIf stringValue = "true" OrElse stringValue = "on" OrElse stringValue = "1" Then
                    value = True
                End If
            Else
                value = stringValue
            End If
 
            Return value
        End Function
 
        ''' 
        ''' Read and cache the request body
        ''' 
        '''
        ''' 
        Private Function TryReadBody(request As HttpRequestMessage) As NameValueCollection
            Dim result As Object
 
            ' try to read out of cache first
            If Not request.Properties.TryGetValue(MultipleBodyParameters, result) Then
                Dim contentType = request.Content.Headers.ContentType
 
 
 
                If contentType IsNot Nothing Then
 
                    Select Case contentType.MediaType
                        Case "application/json"
                            If True Then
                                If AllowJsonContentType Then
                                    result = request.Content.ReadAsStringAsync().Result
                                    request.Properties.Add(MultipleBodyParametersRaw, result)
                                    Dim values = JsonConvert.DeserializeObject(Of Dictionary(Of String, String))(result.ToString())
                                    result = values.Aggregate(New NameValueCollection(), Function(seed, current)
                                                                                             seed.Add(current.Key, current.Value)
                                                                                             Return seed
 
                                                                                         End Function)
 
 
 
                                    request.Properties.Add(MultipleBodyParameters, result)
                                End If
 
                            End If
                            Exit Select
                        Case "application/x-www-form-urlencoded"
                            result = request.Content.ReadAsFormDataAsync().Result
                            request.Properties.Add(MultipleBodyParameters, result)
                            Exit Select
                    End Select
                End If
            End If
 
 
            Return TryCast(result, NameValueCollection)
        End Function
 
        Private Structure AsyncVoid
        End Structure
    End Class
 
End Namespace

Imports System.Web.Http
Imports CC.Net
 
 
Public Class Global_asax
    Inherits HttpApplication
 
    Sub Application_Start(sender As Object, e As EventArgs)
        ' Fires when the application is started
 
        ' It is important this goes before the Routing line: GlobalConfiguration.Configure(AddressOf WebApiConfig.Register)
        GlobalConfiguration.Configuration.ParameterBindingRules.Insert(0, AddressOf CC.Net.WebApi.SimplePostVariableParameterBinding.HookupParameterBinding)
 
        GlobalConfiguration.Configure(AddressOf WebApiConfig.Register)
 
    End Sub
End Class

    API test

     _
    Public Function PostMultipleSimpleValues(make As String, model As String) As String
        Return String.Format("Make: {0}, Model: {1}", make, model)
    End Function

Imports System.Net
Imports System.Web.Http
Imports System.Net.Http
 
Public Class CarsController
    Inherits ApiController
    Private cars As Car() = New Car() _
        {New Car() With { _
        .Id = 1, _
        .Make = "Aston Martin", _
        .Model = "V8 Vantage" _
    }, New Car() With { _
        .Id = 2, _
        .Make = "BMW", _
        .Model = "Z8" _
    }, New Car() With { _
        .Id = 3, _
        .Make = "Ferrari", _
        .Model = "California" _
    }, New Car() With { _
        .Id = 4, _
        .Make = "Pagani", _
        .Model = "Zonda" _
    }}
 
    Public Function GetCars() As IEnumerable(Of Car)
        Return cars
    End Function
 
    '' POST: api/Test
    'Public Sub PostValue(<FromBody()> ByVal value As String)
 
    'End Sub
 
    ' _
    'Public Function PostMultipleSimpleValues(name As String, value As Integer, entered As DateTime, Optional action As String = Nothing) As String
    '    Return String.Format("Name: {0}, Value: {1}, Date: {2}, Action: {3}", name, value, entered, action)
    'End Function
 
     _
    Public Function PostMultipleSimpleValues(make As String, model As String) As String
        Return String.Format("Make: {0}, Model: {1}", make, model)
    End Function
 
 
End Class