Override VFXPropertyAttribute equals to make it correct. (#73)

* Override VFXPropertyAttribute equals to make it correct.

* Update CHANGELOG.md

Author: iTris666

com.unity.visualeffectgraph/CHANGELOG.md

@@ -85,6 +85,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Subgraphs are not in hardcoded categories anymore : updated default subgraph templates + Samples to add meaningful categories.
 - Enum fields having headers show the header in the inspector as well.
 - Fix incorrect propagation on expression flags [Case 1246738](https://issuetracker.unity3d.com/product/unity/issues/guid/1246738/)
+- Fix multiple undos [Case 1262133](https://issuetracker.unity3d.com/product/unity/issues/guid/1262133/)
 
 ## [8.1.0] - 2020-04-21
 

com.unity.visualeffectgraph/Editor/Types/VFXPropertyAttribute.cs

@@ -72,6 +72,30 @@ public static bool IsEqual(VFXPropertyAttribute[] one,VFXPropertyAttribute[] oth
             return true;
         }
 
+
+        public override bool Equals(object obj)
+        {
+            if (!(obj is VFXPropertyAttribute other))
+                return false;
+
+            return m_Type == other.m_Type && m_Min == other.m_Min && m_Max == other.m_Max && m_Tooltip == other.m_Tooltip && m_Regex == other.m_Regex && m_RegexMaxLength == other.m_RegexMaxLength;
+        }
+
+        public override int GetHashCode()
+        {
+            int hashCode = (int)m_Type;
+
+            hashCode += 23 * m_Min.GetHashCode();
+            hashCode += 23 * m_Max.GetHashCode();
+            if(m_Tooltip != null)
+                hashCode += 23 * m_Tooltip.GetHashCode();
+            if (m_Regex != null)
+                hashCode += 23 * m_Regex.GetHashCode();
+            hashCode += 23 * m_RegexMaxLength;
+
+            return hashCode;
+        }
+
         public static VFXExpression ApplyToExpressionGraph(VFXPropertyAttribute[] attributes, VFXExpression exp)
                 {
             if (attributes != null)