adding validation method for vehicle (test) in GUI

VECTO/Input Files/Vehicle.vb

@@ -11,6 +11,7 @@
 Option Infer On
 
 Imports System.Collections.Generic
+Imports System.ComponentModel.DataAnnotations
 Imports System.IO
 Imports System.Linq
 Imports Newtonsoft.Json.Linq
@@ -20,7 +21,7 @@ Imports TUGraz.VectoCommon.Utils
 Imports TUGraz.VectoCore.InputData.FileIO.JSON
 Imports TUGraz.VectoCore.Models.Declaration
 
-
+<CustomValidation(GetType(Vehicle), "ValidateVehicle")>
 Public Class Vehicle
 	'V2 MassMax is now saved in [t] instead of [kg]
 	Private Const FormatVersion As Short = 7
@@ -37,7 +38,7 @@ Public Class Vehicle
 	Public CrossWindCorrectionMode As CrossWindCorrectionMode
 	Public ReadOnly CrossWindCorrectionFile As SubPath
 
-	Public RetarderType As RetarderType
+	<ValidateObject()> Public RetarderType As RetarderType
 	Public RetarderRatio As Double = 0
 	Public ReadOnly RetarderLossMapFile As SubPath
 
@@ -83,6 +84,11 @@ Public Class Vehicle
 		SetDefault()
 	End Sub
 
+
+	Public Shared Function ValidateVehicle(vehicle As Vehicle, validationContext As ValidationContext) As ValidationResult
+		Return New ValidationResult("bla")
+	End Function
+
 	Private Sub SetDefault()
 		Mass = 0
 		MassExtra = 0
@@ -251,6 +257,13 @@ Public Class Vehicle
 	Public Function SaveFile() As Boolean
 		SavedInDeclMode = Cfg.DeclMode
 
+		Dim validationResults = Validate(If(Cfg.DeclMode, ExecutionMode.Declaration, ExecutionMode.Engineering))
+
+		If validationResults.Count > 0 Then
+			MsgBox(String.Format("Invalid input: \n{0}", String.Join("; ", validationResults)), MsgBoxStyle.OkOnly, "Failed to save vehicle")
+			Return False
+		End If
+
 		Dim json As New JSONParser
 		'Header
 		Dim header As Dictionary(Of String, Object) = New Dictionary(Of String, Object) From {