diff --git a/README.md b/README.md
index 857a252f..ee131183 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,7 @@ DefaultEcs is an [Entity Component System](https://en.wikipedia.org/wiki/Entity_
 [![NuGet](https://buildstats.info/nuget/DefaultEcs)](https://www.nuget.org/packages/DefaultEcs)
 [![Coverage Status](https://coveralls.io/repos/github/Doraku/DefaultEcs/badge.svg?branch=master)](https://coveralls.io/github/Doraku/DefaultEcs?branch=master)
 ![continuous integration status](https://github.com/doraku/defaultecs/workflows/continuous%20integration/badge.svg)
+[![preview package](https://img.shields.io/badge/preview-package-blue?style=flat&logo=github)](https://github.com/Doraku/DefaultEcs/packages/26448)
 
 - [Requirement](#Requirement)
 - [Versioning](#Versioning)
diff --git a/documentation/RELEASENOTE.md b/documentation/RELEASENOTE.md
index ecda6123..12822f73 100644
--- a/documentation/RELEASENOTE.md
+++ b/documentation/RELEASENOTE.md
@@ -1,3 +1,15 @@
+## DefaultEcs 0.12.1
+fixed serialization of struct as an object  
+fixed serialization of Type  
+fixed AResourceManager.Manage for existing entities  
+
+added netstandard2.1 target  
+added == and != operators on Entity  
+added internal version on Entity, Entity.IsAlive will return false if a stored disposed entity is reused  
+added a helper ManagedResource static class to create ManagedResource  
+
+[nuget package](https://www.nuget.org/packages/DefaultEcs/0.12.1)
+
 ## DefaultEcs 0.12.0
 breaking change:  
 renamed EntitySetBuilder.WithAny and WithAny attribute to WithEither  
diff --git a/documentation/api/DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo).md b/documentation/api/DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo).md
new file mode 100644
index 00000000..c6b00175
--- /dev/null
+++ b/documentation/api/DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo).md
@@ -0,0 +1,20 @@
+#### [DefaultEcs](./index.md 'index')
+### [DefaultEcs.Resource](./DefaultEcs-Resource.md 'DefaultEcs.Resource').[ManagedResource<TResource>](./DefaultEcs-Resource-ManagedResource-TResource-.md 'DefaultEcs.Resource.ManagedResource<TResource>')
+## ManagedResource<TResource>.Create<TInfo>(TInfo) Method
+Create a [ManagedResource<TInfo,TResource>](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource<TInfo,TResource>') object  
+```C#
+public static DefaultEcs.Resource.ManagedResource<TInfo,TResource> Create<TInfo>(TInfo info);
+```
+#### Type parameters
+<a name='DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo)-TInfo'></a>
+`TInfo`  
+The infos used to identify the resources.  
+  
+#### Parameters
+<a name='DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo)-info'></a>
+`info` [TInfo](#DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo)-TInfo 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;.Create&lt;TInfo&gt;(TInfo).TInfo')  
+The info used to identify the resource.  
+  
+#### Returns
+[DefaultEcs.Resource.ManagedResource&lt;](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;')[TInfo](#DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo)-TInfo 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;.Create&lt;TInfo&gt;(TInfo).TInfo')[,](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;')[TResource](./DefaultEcs-Resource-ManagedResource-TResource-.md#DefaultEcs-Resource-ManagedResource-TResource--TResource 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;.TResource')[&gt;](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;')  
+The [ManagedResource&lt;TInfo,TResource&gt;](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;') object.  
diff --git a/documentation/api/DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo--).md b/documentation/api/DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo--).md
new file mode 100644
index 00000000..b335a24a
--- /dev/null
+++ b/documentation/api/DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo--).md
@@ -0,0 +1,20 @@
+#### [DefaultEcs](./index.md 'index')
+### [DefaultEcs.Resource](./DefaultEcs-Resource.md 'DefaultEcs.Resource').[ManagedResource&lt;TResource&gt;](./DefaultEcs-Resource-ManagedResource-TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;')
+## ManagedResource&lt;TResource&gt;.Create&lt;TInfo&gt;(TInfo[]) Method
+Create a [ManagedResource&lt;TInfo,TResource&gt;](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;') object with multiple infos.  
+```C#
+public static DefaultEcs.Resource.ManagedResource<TInfo[],TResource> Create<TInfo>(params TInfo[] infos);
+```
+#### Type parameters
+<a name='DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo--)-TInfo'></a>
+`TInfo`  
+The infos used to identify the resources.  
+  
+#### Parameters
+<a name='DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo--)-infos'></a>
+`infos` [TInfo](#DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo--)-TInfo 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;.Create&lt;TInfo&gt;(TInfo[]).TInfo')[[]](https://docs.microsoft.com/en-us/dotnet/api/System.Array 'System.Array')  
+The type used to identify a resource.  
+  
+#### Returns
+[DefaultEcs.Resource.ManagedResource&lt;](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;')[TInfo](#DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo--)-TInfo 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;.Create&lt;TInfo&gt;(TInfo[]).TInfo')[[]](https://docs.microsoft.com/en-us/dotnet/api/System.Array 'System.Array')[,](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;')[TResource](./DefaultEcs-Resource-ManagedResource-TResource-.md#DefaultEcs-Resource-ManagedResource-TResource--TResource 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;.TResource')[&gt;](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;')  
+The [ManagedResource&lt;TInfo,TResource&gt;](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;') object.  
diff --git a/documentation/api/DefaultEcs-Resource-ManagedResource-TResource-.md b/documentation/api/DefaultEcs-Resource-ManagedResource-TResource-.md
new file mode 100644
index 00000000..e09c094a
--- /dev/null
+++ b/documentation/api/DefaultEcs-Resource-ManagedResource-TResource-.md
@@ -0,0 +1,16 @@
+#### [DefaultEcs](./index.md 'index')
+### [DefaultEcs.Resource](./DefaultEcs-Resource.md 'DefaultEcs.Resource')
+## ManagedResource&lt;TResource&gt; Class
+Provides static methods for creating [ManagedResource&lt;TInfo,TResource&gt;](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;') object.  
+```C#
+public static class ManagedResource<TResource>
+```
+Inheritance [System.Object](https://docs.microsoft.com/en-us/dotnet/api/System.Object 'System.Object') &gt; [ManagedResource&lt;TResource&gt;](./DefaultEcs-Resource-ManagedResource-TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;')  
+#### Type parameters
+<a name='DefaultEcs-Resource-ManagedResource-TResource--TResource'></a>
+`TResource`  
+The type of the resource.  
+  
+### Methods
+- [Create&lt;TInfo&gt;(TInfo)](./DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo).md 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;.Create&lt;TInfo&gt;(TInfo)')
+- [Create&lt;TInfo&gt;(TInfo[])](./DefaultEcs-Resource-ManagedResource-TResource--Create-TInfo-(TInfo--).md 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;.Create&lt;TInfo&gt;(TInfo[])')
diff --git a/documentation/api/DefaultEcs-Resource.md b/documentation/api/DefaultEcs-Resource.md
index dfdb7aac..adafcf0c 100644
--- a/documentation/api/DefaultEcs-Resource.md
+++ b/documentation/api/DefaultEcs-Resource.md
@@ -3,5 +3,6 @@
 The [DefaultEcs.Resource](./DefaultEcs-Resource.md 'DefaultEcs.Resource') namespace contains types used in the loading of unmanaged resources needed as components.  
 ### Classes
 - [AResourceManager&lt;TInfo,TResource&gt;](./DefaultEcs-Resource-AResourceManager-TInfo_TResource-.md 'DefaultEcs.Resource.AResourceManager&lt;TInfo,TResource&gt;')
+- [ManagedResource&lt;TResource&gt;](./DefaultEcs-Resource-ManagedResource-TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TResource&gt;')
 ### Structs
 - [ManagedResource&lt;TInfo,TResource&gt;](./DefaultEcs-Resource-ManagedResource-TInfo_TResource-.md 'DefaultEcs.Resource.ManagedResource&lt;TInfo,TResource&gt;')
diff --git a/source/DefaultEcs/DefaultEcs.Release.csproj b/source/DefaultEcs/DefaultEcs.Release.csproj
index f843c484..e8d16eca 100644
--- a/source/DefaultEcs/DefaultEcs.Release.csproj
+++ b/source/DefaultEcs/DefaultEcs.Release.csproj
@@ -11,7 +11,7 @@
   </ItemGroup>
 
   <PropertyGroup Label="Package">
-    <Version>0.12.1-alpha1</Version>
+    <Version>0.12.1</Version>
     <PackageReleaseNotes>
 fixed serialization of struct as an object
 fixed serialization of Type