Added IgnoreDifferences attribute

Author: igece

README.md

@@ -33,8 +33,6 @@ dotnet add package ObjDiff
 
 ## Current Limitations
 
-This library is still in an early stage of development and so it lacks some features that similar libraries can offer:
-
 * Only allows to compare objects of the same type
 * Only public properties are compared
 
@@ -102,6 +100,13 @@ public class CompareOptions
 }
 ```
 
+### Ignoring Properties
+
+Any property marked with the `IgnoreDifferences` attribute will always be skipped during the comparison process, no matter
+the actual value of the `IgnoredAttributes` property if `CompareOptions` is used.
+
+The usage of this attribute
+
 ### Patching
 
 Once we have the differences between two objects, we can apply them (patch) to the original object being compared. After patching it, both objects should be equivalent.

src/ObjDiff/IgnoreDifferencesAttribute.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace ObjDiff
+{
+    [AttributeUsage(AttributeTargets.Property)]
+    public class IgnoreDifferencesAttribute : Attribute
+    {
+    }
+}

src/ObjDiff/ObjDiff.cs

@@ -144,7 +144,7 @@ private static IEnumerable<Difference> Diff<T>(T left, T right, CompareOptions c
         compareOptions = new CompareOptions();
 
       var applicableProperties = left.GetType().GetProperties().Where(p => !compareOptions.IgnoredProperties.Contains(p.Name) &&
-        !p.GetCustomAttributes(false).Any(x => compareOptions.IgnoredAttributes.Contains(x.GetType().Name)));
+        !p.GetCustomAttributes(false).Any(x => x.GetType() == typeof(IgnoreDifferencesAttribute) || compareOptions.IgnoredAttributes.Contains(x.GetType().Name)));
 
       foreach (var property in applicableProperties)
       {

src/ObjDiff/ObjDiff.csproj

@@ -12,8 +12,8 @@
     <Authors>Israel Gómez de Celis González</Authors>
     <Description>A C# .NET Standard library that allows to obtain the differences between two objects and, optionally, patch the first object with these differences so it becomes equal to the second one.</Description>
     <Copyright>Copyright (c) 2021 Israel Gómez de Celis González</Copyright>
-    <Version>1.2.0</Version>
-    <PackageReleaseNotes>Added method MakeEqual as a shortcut to call Diff followed by Patch.</PackageReleaseNotes>
+    <Version>1.3.0</Version>
+    <PackageReleaseNotes>New IgnoreDifferences attribute. Any property marked with this attribute will be always ignored.</PackageReleaseNotes>
   </PropertyGroup>
 
   <ItemGroup>