From 42a383343b2b7624fb05efd5253064d9102746de Mon Sep 17 00:00:00 2001
From: CanHua Li <licanhua@live.com>
Date: Fri, 13 Dec 2019 11:23:53 -0800
Subject: [PATCH 1/2] delete pch after build

---
 vnext/Directory.Build.targets | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/vnext/Directory.Build.targets b/vnext/Directory.Build.targets
index a93bc8eb44d..4eab5541e64 100644
--- a/vnext/Directory.Build.targets
+++ b/vnext/Directory.Build.targets
@@ -47,4 +47,26 @@
     <Message Text="=> VCTargetsPath           [$(VCTargetsPath)]" />
   </Target>
 
+  <Target Name="_ComputePrecompToCleanUp">
+    <ItemGroup>
+      <PCHFileToClean Include="$(IntDir)\**\*.pch" />
+      <_PCHFileToCleanWithTimestamp Include="@(PCHFileToClean)" Condition="'%(Identity)' != ''">
+        <LastWriteTime>$([System.IO.File]::GetLastWriteTime('%(Identity)'))</LastWriteTime>
+      </_PCHFileToCleanWithTimestamp>
+    </ItemGroup>
+  </Target>
+  <!-- 
+    As a cppwinrt project, .pch is very big, and delete it in pipeline after build
+    Instead of outright deleting the PCHs, we want to trick the "project freshness detector" by
+    emitting empty files that look suspiciously like the PCHs it's expecting.
+    It's of utmost importance that their timestamps match up. -->
+  <Target Name="CleanUpPrecompHeaders"
+          DependsOnTargets="_ComputePrecompToCleanUp"
+          AfterTargets="AfterBuild"
+          Condition="'$(AGENT_ID)' != ''">
+    <!-- We just need to keep *ReactNativeWindows*'s PCHs because they get rebuilt more often. -->
+    <Delete Files="@(_PCHFileToCleanWithTimestamp)"/>
+    <Touch Files="@(_PCHFileToCleanWithTimestamp)" Time="%(LastWriteTime)" AlwaysCreate="true" />
+    <Message Text="PCH and Precomp object @(_PCHFileToCleanWithTimestamp) has been deleted for $(ProjectName)." />
+  </Target>
 </Project>
\ No newline at end of file

From ba7db6a2990b5f566c06b811869b8e58743dda61 Mon Sep 17 00:00:00 2001
From: CanHua Li <licanhua@live.com>
Date: Fri, 13 Dec 2019 11:33:23 -0800
Subject: [PATCH 2/2] Change files

---
 ...eact-native-windows-2019-12-13-11-33-23-PCHDelete.json | 8 ++++++++
 1 file changed, 8 insertions(+)
 create mode 100644 change/react-native-windows-2019-12-13-11-33-23-PCHDelete.json

diff --git a/change/react-native-windows-2019-12-13-11-33-23-PCHDelete.json b/change/react-native-windows-2019-12-13-11-33-23-PCHDelete.json
new file mode 100644
index 00000000000..c64f10b37d0
--- /dev/null
+++ b/change/react-native-windows-2019-12-13-11-33-23-PCHDelete.json
@@ -0,0 +1,8 @@
+{
+  "type": "none",
+  "comment": "Delete .PCH ",
+  "packageName": "react-native-windows",
+  "email": "licanhua@live.com",
+  "commit": "42a383343b2b7624fb05efd5253064d9102746de",
+  "date": "2019-12-13T19:33:23.242Z"
+}
\ No newline at end of file