From a4d510e6bef9560a44289a6c19178756fc88efc9 Mon Sep 17 00:00:00 2001
From: Chris R <Tratcher@outlook.com>
Date: Wed, 14 Jul 2021 11:18:08 -0700
Subject: [PATCH 1/2] Use preview langversion and ignore duplicate using
 warnings

---
 Directory.Build.props           | 3 ++-
 eng/targets/CSharp.Common.props | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/Directory.Build.props b/Directory.Build.props
index ba1c1675a099..bb558bd9d8c6 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -1,4 +1,4 @@
-<Project>
+<Project>
   <Import Project="eng\Common.props" />
 
   <PropertyGroup>
@@ -111,6 +111,7 @@
   <PropertyGroup>
     <!-- Ensure API docs are available. -->
     <NoWarn>$(NoWarn.Replace('1591', ''))</NoWarn>
+    <NoWarn>$(NoWarn);0105</NoWarn>
 
     <!-- For local builds, don't make missing XML docs a fatal build error, but still surface so we have visibility into undocumented APIs. -->
     <WarningsNotAsErrors Condition=" '$(ContinuousIntegrationBuild)' != 'true' ">$(WarningsNotAsErrors);CS1591</WarningsNotAsErrors>
diff --git a/eng/targets/CSharp.Common.props b/eng/targets/CSharp.Common.props
index b97198a89136..3a6656748947 100644
--- a/eng/targets/CSharp.Common.props
+++ b/eng/targets/CSharp.Common.props
@@ -1,7 +1,7 @@
 <Project>
 
   <PropertyGroup>
-    <LangVersion>10.0</LangVersion>
+    <LangVersion>preview</LangVersion>
 
     <!-- Enables Strict mode for Roslyn compiler -->
     <Features>strict;nullablePublicOnly</Features>

From dfe751199af2a719bc726bb558529b1125fccda9 Mon Sep 17 00:00:00 2001
From: Chris R <Tratcher@outlook.com>
Date: Wed, 14 Jul 2021 12:31:02 -0700
Subject: [PATCH 2/2] Conditional nowarn

---
 Directory.Build.props | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Directory.Build.props b/Directory.Build.props
index bb558bd9d8c6..4a5a32268ec6 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -111,7 +111,7 @@
   <PropertyGroup>
     <!-- Ensure API docs are available. -->
     <NoWarn>$(NoWarn.Replace('1591', ''))</NoWarn>
-    <NoWarn>$(NoWarn);0105</NoWarn>
+    <NoWarn Condition=" '$(BuildingInsideVisualStudio)' == 'true' ">$(NoWarn);0105</NoWarn>
 
     <!-- For local builds, don't make missing XML docs a fatal build error, but still surface so we have visibility into undocumented APIs. -->
     <WarningsNotAsErrors Condition=" '$(ContinuousIntegrationBuild)' != 'true' ">$(WarningsNotAsErrors);CS1591</WarningsNotAsErrors>