From 29f96b670eefd16af32e8d684eacba23b41e0dd9 Mon Sep 17 00:00:00 2001
From: Mohammadreza Taikandi <mrtaikandi@hotmail.com>
Date: Tue, 22 Dec 2020 08:20:49 +0000
Subject: [PATCH] Add initial readme content.

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 README.md | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 86 insertions(+), 1 deletion(-)

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 # MapTo
-An object to object mapping generator using using Roslyn code generator.
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+An object to object mapping generator using using [Roslyn source generator](https://github.com/dotnet/roslyn/blob/master/docs/features/source-generators.md).
+
+## Installation
+```
+dotnet add package MapTo
+```
+
+## Usage
+MapTo creates mappings during compile-time. To indicate which objects it needs to generate the mappings for, simply declare the class as `partial` and annotate it with `MapFrom` attribute.
+
+```c#
+[MapFrom(sourceType: typeof(App.Data.Models.User))]
+public partial class UserViewModel 
+{
+    public string FirstName { get; }
+
+    public string LastName { get; }
+}
+```
+
+If `Data.Models.User` class is defined as follow:
+
+```c#
+namespace App.Data.Models
+{
+    public class User
+    {
+        public User(int id) => Id = id;
+        
+        public int Id { get; }
+
+        public string FirstName { get; set; }
+
+        public string LastName { get; set; }
+
+        public string FullName => $"{FirstName} {LastName}";
+    }
+}
+```
+
+It will generate the following code:
+
+```c#
+// <auto-generated />
+using System;
+
+namespace App.ViewModels
+{
+    public partial class UserViewModel
+    {
+        public UserViewModel(App.Data.Models.User user)
+        {
+            if (user == null) throw new ArgumentNullException(nameof(user));
+            FirstName = user.FirstName;
+            LastName = user.LastName;
+        }
+
+        public static UserViewModel From(App.Data.Models.User user)
+        {
+            return user == null ? null : new UserViewModel(user);
+        }
+    }
+
+    public static partial class UserExtensions
+    {
+        public static UserViewModel ToUserViewModel(this App.Data.Models.User user)
+        {
+            return user == null ? null : new UserViewModel(user);
+        }
+    }
+}
+```
+
+Which makes it possible to get an instance of `UserViewModel` from one of the following ways:
+
+```c#
+var user = new User(id: 10) { FirstName = "John", LastName = "Doe" };
+
+var vm = user.ToUserViewModel();
+
+// OR
+vm = new UserViewModel(user);
+
+// OR
+vm = UserViewModel.From(user);
+```
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