[BUG] Type 'OAProjectItem' is not marked as serializable in VS2022 on files generation

[psulek]

Select category

• LHQ Editor - Visual Studio Extension
• ScaleHQ.WPF.LHQ - NuGet Package
• ScaleHQ.AspNetCore.LHQ - NuGet Package
  (place x inside square brackets to mark category or multiple categories)

Version

2022.1

Visual Studio Edition

• Visual Studio Community
• Visual Studio Pro
• Visual Studio Enterprise
  (place x inside square brackets to mark edition or multiple editions)

Visual Studio Version

• 2015
• 2017
• 2019
• 2022
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Describe Problem

Generating files in VS2022 throws error:

Type 'Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.Automation.OAProjectItem' in Assembly 'Microsoft.VisualStudio.ProjectSystem.VS.Implementation, Version=17.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable.'

[psulek]

Found forum with same error:
http://vfrdtyky.blogspot.com/2019/04/visual-studio-serialization-error-when.html

possible fix:

The EnvDTE assemblies are COM interop assemblies. Your error can be avoided by creating a Runtime Callable Wrapper, which marshals calls to the COM object based off information in the interop-assembly. Microsoft has provided an extension method within the
Microsoft.VisualStudio.TextTemplating namespace:



<#@ template hostspecific="true" language="C#" #>

<#@ assembly name="EnvDTE" #>

<#@ import namespace="Microsoft.VisualStudio.TextTemplating" #>

<#

  IServiceProvider serviceProvider = (IServiceProvider)this.Host;

  EnvDTE.DTE dte = (EnvDTE.DTE) serviceProvider.GetCOMService(typeof(EnvDTE.DTE));

 #>



The GetCOMService(this IServiceProvider, Type type) extension method is the correct way to obtain the DTE COM object.



T4 templates run in a separate AppDomain, and I believe that is the reason your code is working despite the exception. IServiceProvider.GetService(typeof(DTE)) returns a transparent Proxy Object. This exception is because the proxy requires objects crossing an app domain be decorated with the Serializable attribute. You can confirm the DTE object in your code is a "transparent proxy" like this:



bool isProxy = RemotingServices.IsTransparentProxy(dte); 

[psulek]

fixed in Release v2022.2