Major refactor.

Core now formed and contains all useful utility to create custom ui with restrictions.
Many methods was extracted from different classes and moved to core.

Undo is now supported(because unity's undo bug seems to be fixed).

Example now moved into same level separate folder.

Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceButtonAttribute.meta

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Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceButtonAttribute/SerializeReferenceButtonAttribute.cs

@@ -0,0 +1,8 @@
+using System;
+using UnityEngine;
+
+[AttributeUsage(AttributeTargets.Field)]
+public class SerializeReferenceButtonAttribute : PropertyAttribute
+{
+    
+}

Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceButtonAttribute/SerializeReferenceButtonAttribute.cs.meta

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Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceButtonAttribute/SerializeReferenceButtonAttributeDrawer.cs

@@ -0,0 +1,31 @@
+#if UNITY_EDITOR
+
+using UnityEditor; 
+using UnityEngine;
+
+[CustomPropertyDrawer(typeof(SerializeReferenceButtonAttribute))]
+public class SerializeReferenceButtonAttributeDrawer : PropertyDrawer
+{
+    public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
+    {
+        return EditorGUI.GetPropertyHeight(property, true);
+    }
+ 
+    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
+    {
+
+        
+        EditorGUI.BeginProperty(position, label, property); 
+        
+        var labelPosition = new Rect(position.x, position.y, position.width, EditorGUIUtility.singleLineHeight);
+        EditorGUI.LabelField(labelPosition, label);    
+         
+        var typeRestrictions = SerializedReferenceUIDefaultTypeRestrictions.GetAllBuiltInTypeRestrictions(fieldInfo);
+        property.DrawSelectionButtonForManagedReference(position, typeRestrictions);
+        
+        EditorGUI.PropertyField(position, property, GUIContent.none, true);
+        
+        EditorGUI.EndProperty(); 
+    } 
+}
+#endif

Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceButtonAttribute/SerializeReferenceButtonAttributeDrawer.cs.meta

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Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceMenuAttribute.meta

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Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceMenuAttribute/SerializeReferenceMenuAttribute.cs

@@ -0,0 +1,8 @@
+using System;
+using UnityEngine;
+
+[AttributeUsage(AttributeTargets.Field)]
+public class SerializeReferenceMenuAttribute : PropertyAttribute
+{
+    
+}

Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceMenuAttribute/SerializeReferenceMenuAttribute.cs.meta

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Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceMenuAttribute/SerializeReferenceMenuAttributeDrawer.cs

@@ -0,0 +1,26 @@
+#if UNITY_EDITOR
+
+using UnityEditor;
+using UnityEngine;
+
+[CustomPropertyDrawer(typeof(SerializeReferenceMenuAttribute))]
+public class SerializeReferenceMenuAttributeDrawer : PropertyDrawer
+{
+    public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
+    {
+        return EditorGUI.GetPropertyHeight(property, true);
+    }
+
+    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
+    {
+        EditorGUI.BeginProperty(position, label, property);
+        
+        var typeRestrictions = SerializedReferenceUIDefaultTypeRestrictions.GetAllBuiltInTypeRestrictions(fieldInfo);
+        property.ShowContextMenuForManagedReferenceOnMouseMiddleButton(position, typeRestrictions);
+        
+        EditorGUI.PropertyField(position, property, true);
+        EditorGUI.EndProperty();
+    }
+}
+#endif
+

Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceMenuAttribute/SerializeReferenceMenuAttributeDrawer.cs.meta

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Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceUIRestrictionExcludeTypes.meta

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Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceUIRestrictionExcludeTypes/SerializeReferenceUIRestrictionExcludeTypes.cs

@@ -0,0 +1,10 @@
+using System;
+using UnityEngine;
+
+/// None of this types or interface types are valid.
+[AttributeUsage(AttributeTargets.Field)]
+public class SerializeReferenceUIRestrictionExcludeTypes : PropertyAttribute
+{
+    public readonly Type[] Types;
+    public SerializeReferenceUIRestrictionExcludeTypes(params Type[] types) => Types = types;
+} 

Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceUIRestrictionExcludeTypes/SerializeReferenceUIRestrictionExcludeTypes.cs.meta

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Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceUIRestrictionIncludeTypes.meta

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Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceUIRestrictionIncludeTypes/SerializeReferenceUIRestrictionIncludeTypes.cs

@@ -0,0 +1,10 @@
+using System;
+using UnityEngine;
+
+/// Any of this types or interface types are valid. And only this types can be presented.
+[AttributeUsage(AttributeTargets.Field)]
+public class SerializeReferenceUIRestrictionIncludeTypes : PropertyAttribute
+{
+    public readonly Type[] Types;
+    public SerializeReferenceUIRestrictionIncludeTypes(params Type[] types) => Types = types;
+}

Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializeReferenceUIRestrictionIncludeTypes/SerializeReferenceUIRestrictionIncludeTypes.cs.meta

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Assets/Textus/SerializeReferenceUI/DefaultAttributes/SerializedReferenceUIDefaultTypeRestrictions.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+
+public static class SerializedReferenceUIDefaultTypeRestrictions
+{
+    public static IEnumerable<Func<Type, bool>> GetAllBuiltInTypeRestrictions(FieldInfo fieldInfo)
+    {
+        var result = new List<Func<Type, bool>>();
+        
+        var attributeObjects = fieldInfo.GetCustomAttributes(false);
+        foreach (var attributeObject in attributeObjects)
+        {
+            switch (attributeObject)
+            { 
+                case SerializeReferenceUIRestrictionIncludeTypes includeTypes:
+                    result.Add(SerializeReferenceTypeRestrictionFilters.TypeIsSubclassOrEqualOrHasInterface(includeTypes.Types)); 
+                    continue;
+                case SerializeReferenceUIRestrictionExcludeTypes excludeTypes:
+                    result.Add(SerializeReferenceTypeRestrictionFilters.TypeIsNotSubclassOrEqualOrHasInterface(excludeTypes.Types)); 
+                    continue;
+            } 
+        }
+        return result; 
+    }
+} 

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