Update sample project.

test/TestConsoleApp/Data/Models/Profile.cs

@@ -0,0 +1,11 @@
+namespace TestConsoleApp.Data.Models
+{
+    public class Profile
+    {
+        public string FirstName { get; set; }
+
+        public string LastName { get; set; }
+
+        public string FullName => $"{FirstName} {LastName}";
+    }
+}

test/TestConsoleApp/Data/Models/User.cs

@@ -1,15 +1,13 @@
-namespace TestConsoleApp.Data.Models
+using System;
+
+namespace TestConsoleApp.Data.Models
 {
     public class User
     {
         public int Id { get; set; }
 
-        public string FirstName { get; set; }
+        public DateTimeOffset RegisteredAt { get; set; }
 
-        public string LastName { get; set; }
-
-        public string FullName => $"{FirstName} {LastName}";
-        
-        public long Key { get; }
+        public Profile Profile { get; set; }
     }
 }

test/TestConsoleApp/Program.cs

@@ -1,4 +1,6 @@
-using TestConsoleApp.ViewModels;
+using System;
+using TestConsoleApp.Data.Models;
+using TestConsoleApp.ViewModels;
 
 namespace TestConsoleApp
 {
@@ -6,8 +8,23 @@ namespace TestConsoleApp
     {
         private static void Main(string[] args)
         {
-            var userViewModel = User.From(new Data.Models.User());
-            var userViewModel2 = new Data.Models.User().ToUserViewModel();
+            var user = new User
+            {
+                Id = 1234,
+                RegisteredAt = DateTimeOffset.Now,
+                Profile = new Profile
+                {
+                    FirstName = "John",
+                    LastName = "Doe"
+                }
+            };
+
+            var vm = user.ToUserViewModel();
+
+            Console.WriteLine("Key: {0}", vm.Key);
+            Console.WriteLine("RegisteredAt: {0}", vm.RegisteredAt);
+            Console.WriteLine("FirstName: {0}", vm.Profile.FirstName);
+            Console.WriteLine("LastName: {0}", vm.Profile.LastName);
         }
     }
 }

test/TestConsoleApp/TestConsoleApp.csproj

@@ -3,8 +3,8 @@
     <PropertyGroup>
         <OutputType>Exe</OutputType>
         <TargetFramework>netcoreapp3.1</TargetFramework>
-        <LangVersion>8</LangVersion>
-        <Nullable>annotations</Nullable>
+        <LangVersion>7.3</LangVersion>
+        <Nullable>disable</Nullable>
     </PropertyGroup>
 
     <ItemGroup>

test/TestConsoleApp/ViewModels/ProfileViewModel.cs

@@ -1,14 +1,13 @@
-// using MapTo;
-
-using MapTo;
+using MapTo;
+using TestConsoleApp.Data.Models;
 
 namespace TestConsoleApp.ViewModels
 {
-    [MapFrom(typeof(Data.Models.User))]
-    public partial class User
+    [MapFrom(typeof(Profile))]
+    public partial class ProfileViewModel
     {
         public string FirstName { get; }
-        
+
         public string LastName { get; }
     }
 }

test/TestConsoleApp/ViewModels/UserViewModel.cs

@@ -1,22 +1,24 @@
-using MapTo;
+using System;
+using MapTo;
+using TestConsoleApp.Data.Models;
 
 namespace TestConsoleApp.ViewModels
 {
-    [MapFrom(typeof(Data.Models.User))]
+    [MapFrom(typeof(User))]
     public partial class UserViewModel
     {
-        public string FirstName { get; }
-
-        [IgnoreProperty]
-        public string LastName { get; }
-        
-        [MapTypeConverter(typeof(LastNameConverter))]
+        [MapProperty(SourcePropertyName = nameof(User.Id))]
+        [MapTypeConverter(typeof(IdConverter))]
         public string Key { get; }
 
-        private class LastNameConverter : ITypeConverter<long, string>
+        public DateTimeOffset RegisteredAt { get; set; }
+        
+        // [IgnoreProperty]
+        public ProfileViewModel Profile { get; set; }
+
+        private class IdConverter : ITypeConverter<int, string>
         {
-            /// <inheritdoc />
-            public string Convert(long source, object[]? converterParameters) => $"{source} :: With Type Converter";
+            public string Convert(int source, object[] converterParameters) => $"{source:X}";
         }
     }
 }