diff --git a/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/DesignerTests.cs b/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/DesignerTests.cs
index c8288443d5a..ec42201ab0c 100644
--- a/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/DesignerTests.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/DesignerTests.cs
@@ -90,7 +90,8 @@ public CustomTextView(Context context, IAttributeSet attributes) : base(context,
 			using (var libb = CreateDllBuilder (Path.Combine (path, lib.ProjectName), false, false))
 			using (var appb = CreateApkBuilder (Path.Combine (path, proj.ProjectName), false, false)) {
 				// Save the library project, but don't build it yet
-				libb.Save (lib);
+				libb.Save (lib, saveProject: true);
+				FileAssert.Exists (Path.Combine(Root, path, lib.ProjectName, lib.ProjectFilePath));
 				appb.BuildLogFile = "build1.log";
 				appb.Target = target;
 				Assert.IsTrue (appb.Build (proj, parameters: DesignerParameters), $"build should have succeeded for target `{target}`");
@@ -104,10 +105,10 @@ public CustomTextView(Context context, IAttributeSet attributes) : base(context,
 				Assert.IsNotNull (doc.Element ("LinearLayout").Element ("unnamedproject.CustomTextView"),
 					"unnamedproject.CustomTextView should have not been replaced with a $(Hash).CustomTextView");
 				// Build the library project now
-				Assert.IsTrue (libb.Build (lib, doNotCleanupOnUpdate: true), "library build should have succeeded.");
+				Assert.IsTrue (libb.Build (lib, doNotCleanupOnUpdate: true, saveProject: true), "library build should have succeeded.");
 				appb.Target = "Build";
 				appb.BuildLogFile = "build2.log";
-				Assert.IsTrue (appb.Build (proj, doNotCleanupOnUpdate: true), "app build should have succeeded.");
+				Assert.IsTrue (appb.Build (proj, doNotCleanupOnUpdate: true, saveProject: false), "app build should have succeeded.");
 				Assert.IsTrue (appb.Output.AreTargetsAllBuilt ("_UpdateAndroidResgen"), "_UpdateAndroidResgen should have run completely.");
 				Assert.IsTrue (appb.Output.AreTargetsAllBuilt ("_Foo"), "_Foo should have run completely");
 				doc = XDocument.Load (customViewPath);
@@ -117,7 +118,16 @@ public CustomTextView(Context context, IAttributeSet attributes) : base(context,
 					"unnamedproject.CustomTextView should have been replaced with a $(Hash).CustomTextView");
 				appb.Target = target;
 				appb.BuildLogFile = "build3.log";
-				Assert.IsTrue (appb.Build (proj, parameters: DesignerParameters, doNotCleanupOnUpdate: true), $"build should have succeeded for target `{target}`");
+				Assert.IsTrue (appb.DesignTimeBuild (proj, parameters: DesignerParameters, doNotCleanupOnUpdate: true), $"build should have succeeded for target `{target}`");
+				Assert.IsFalse (appb.Output.AreTargetsAllSkipped ("_UpdateAndroidResgen"), "_UpdateAndroidResgen should not have been skipped.");
+				Assert.IsTrue (appb.Output.AreTargetsAllBuilt ("_Foo"), "_Foo should have run completely");
+				doc = XDocument.Load (customViewPath);
+				Assert.IsNull (doc.Element ("LinearLayout").Element ("UnnamedProject.CustomTextView"),
+					"UnnamedProject.CustomTextView should have been replaced with a $(Hash).CustomTextView");
+				Assert.IsNull (doc.Element ("LinearLayout").Element ("unnamedproject.CustomTextView"),
+					"unnamedproject.CustomTextView should have been replaced with a $(Hash).CustomTextView");
+				appb.BuildLogFile = "build4.log";
+				Assert.IsTrue (appb.DesignTimeBuild (proj, parameters: DesignerParameters, doNotCleanupOnUpdate: true), $"build should have succeeded for target `{target}`");
 				Assert.IsTrue (appb.Output.AreTargetsAllSkipped ("_UpdateAndroidResgen"), "_UpdateAndroidResgen should have been skipped.");
 				Assert.IsTrue (appb.Output.AreTargetsAllBuilt ("_Foo"), "_Foo should have run completely");
 				doc = XDocument.Load (customViewPath);
diff --git a/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/IncrementalBuildTest.cs b/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/IncrementalBuildTest.cs
index 55c05640ea6..eba5ef7313b 100644
--- a/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/IncrementalBuildTest.cs
+++ b/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/IncrementalBuildTest.cs
@@ -105,6 +105,11 @@ public void CheckNothingIsDeletedByIncrementalClean ([Values (true, false)] bool
 					File.SetLastWriteTimeUtc (file, DateTime.UtcNow);
 				}
 				Assert.IsTrue (b.Build (proj, doNotCleanupOnUpdate: true, saveProject: false), "Second should have succeeded");
+				b.Output.AssertTargetIsNotSkipped ("_CleanMonoAndroidIntermediateDir");
+				var stampFiles = Path.Combine (intermediate, "stamp", "_ResolveLibraryProjectImports.stamp");
+				FileAssert.Exists (stampFiles, $"{stampFiles} should exists!");
+				var libraryProjectImports = Path.Combine (intermediate, "libraryprojectimports.cache");
+				FileAssert.Exists (libraryProjectImports, $"{libraryProjectImports} should exists!");
 
 				//No changes
 				Assert.IsTrue (b.Build (proj, doNotCleanupOnUpdate: true, saveProject: false), "Third should have succeeded");
@@ -827,6 +832,7 @@ public void ResolveLibraryProjectImports ()
 
 				b.BuildLogFile = "build2.log";
 				Assert.IsTrue (b.Build (proj), "second build should have succeeded.");
+				b.Output.AssertTargetIsNotSkipped ("_ResolveLibraryProjectImports");
 				FileAssert.Exists (cacheFile);
 				var actual = ReadCache (cacheFile);
 				CollectionAssert.AreEqual (actual.Jars.Select (j => j.ItemSpec).OrderBy (j => j),
@@ -867,6 +873,22 @@ public void ResolveLibraryProjectImports ()
 				foreach (var targetName in targets) {
 					Assert.IsTrue (b.Output.IsTargetSkipped (targetName), $"`{targetName}` should be skipped!");
 				}
+
+				var filesToTouch = new [] {
+ 					Path.Combine (intermediate, "build.props"),
+ 					Path.Combine (intermediate, $"{proj.ProjectName}.pdb"),
+ 				};
+				foreach (var file in filesToTouch) {
+					FileAssert.Exists (file);
+					File.SetLastWriteTimeUtc (file, DateTime.UtcNow);
+				}
+
+				b.BuildLogFile = "build5.log";
+				Assert.IsTrue (b.Build (proj), "fifth build should have succeeded.");
+				b.Output.AssertTargetIsNotSkipped ("_CleanMonoAndroidIntermediateDir");
+				b.Output.AssertTargetIsNotSkipped ("_ResolveLibraryProjectImports");
+				FileAssert.Exists (cacheFile);
+				FileAssert.Exists (stamp);
 			}
 		}
 
@@ -1157,13 +1179,16 @@ public void DesignTimeBuild ()
 			var proj = new XamarinAndroidApplicationProject ();
 			using (var b = CreateApkBuilder (Path.Combine ("temp", $"{nameof (IncrementalBuildTest)}{TestName}"))) {
 				Assert.IsTrue (b.DesignTimeBuild (proj), "first dtb should have succeeded.");
+				var target = "_ResolveLibraryProjectImports";
+				Assert.IsFalse (b.Output.IsTargetSkipped (target), $"`{target}` should not have been skipped.");
 				// DesignTimeBuild=true lowercased
 				var parameters = new [] { "DesignTimeBuild=true" };
 				Assert.IsTrue (b.RunTarget (proj, "Compile", doNotCleanupOnUpdate: true, parameters: parameters), "second dtb should have succeeded.");
-				var target = "_ResolveLibraryProjectImports";
 				Assert.IsTrue (b.Output.IsTargetSkipped (target), $"`{target}` should have been skipped.");
 				Assert.IsTrue (b.RunTarget (proj, "UpdateGeneratedFiles", doNotCleanupOnUpdate: true, parameters: parameters), "UpdateGeneratedFiles should have succeeded.");
 				Assert.IsTrue (b.Output.IsTargetSkipped (target), $"`{target}` should have been skipped.");
+				Assert.IsTrue (b.Build (proj, doNotCleanupOnUpdate: true, saveProject: false), "full build should have succeeded.");
+				Assert.IsFalse (b.Output.IsTargetSkipped (target), $"`{target}` should not have been skipped.");
 			}
 		}
 
diff --git a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
index df1bf28d741..f896c51896f 100644
--- a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
+++ b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets
@@ -910,13 +910,18 @@ because xbuild doesn't support framework reference assemblies.
 		<AndroidLinkResources Condition="'$(AndroidLinkResources)' == '' And '$(AndroidIncludeDebugSymbols)' != 'True'">False</AndroidLinkResources>
 		<_AndroidBuildPropertiesCacheExists Condition=" Exists('$(_AndroidBuildPropertiesCache)') ">True</_AndroidBuildPropertiesCacheExists>
 		<_NuGetAssetsFile      Condition=" Exists('$(ProjectAssetsFile)') ">$(ProjectAssetsFile)</_NuGetAssetsFile>
-		<_NuGetAssetsFile      Condition=" Exists('$(ProjectLockFile)') ">$(ProjectLockFile)</_NuGetAssetsFile>
+		<_NuGetAssetsFile      Condition=" '$(_NuGetAssetsFile)' == '' and Exists('$(ProjectLockFile)') ">$(ProjectLockFile)</_NuGetAssetsFile>
 		<_NuGetAssetsFile      Condition=" '$(_NuGetAssetsFile)' == '' and Exists('packages.config') ">packages.config</_NuGetAssetsFile>
-		<_NuGetAssetsTimestamp Condition=" '$(_NuGetAssetsFile)' != '' ">$([System.IO.File]::GetLastWriteTime('$(_NuGetAssetsFile)').Ticks)</_NuGetAssetsTimestamp>
 		<_TypeMapKind Condition=" '$(AndroidIncludeDebugSymbols)' != 'True' ">mvid</_TypeMapKind>
 		<_TypeMapKind Condition=" '$(AndroidIncludeDebugSymbols)' == 'True' And '$(_InstantRunEnabled)' == 'True' ">strings-files</_TypeMapKind>
 		<_TypeMapKind Condition=" '$(AndroidIncludeDebugSymbols)' == 'True' And '$(_InstantRunEnabled)' != 'True' ">strings-asm</_TypeMapKind>
 	</PropertyGroup>
+	<GetFileHash
+				Condition=" Exists('$(_NuGetAssetsFile)') "
+				Files="$(_NuGetAssetsFile)"
+		>
+			<Output TaskParameter="Items" ItemName="_NuGetAssetsFileHash" />
+	</GetFileHash>
 	<ItemGroup>
 		<!-- List of items we want to trigger a build if changed -->
 		<_PropertyCacheItems Include="AotAssemblies=$(AotAssemblies)" />
@@ -945,7 +950,7 @@ because xbuild doesn't support framework reference assemblies.
 		<_PropertyCacheItems Include="OS=$(OS)" />
 		<_PropertyCacheItems Include="AndroidIncludeDebugSymbols=$(AndroidIncludeDebugSymbols)" />
 		<_PropertyCacheItems Include="AndroidPackageNamingPolicy=$(AndroidPackageNamingPolicy)" />
-		<_PropertyCacheItems Include="_NuGetAssetsTimestamp=$(_NuGetAssetsTimestamp)" />
+		<_PropertyCacheItems Include="_NuGetAssetsFileHash=%(_NuGetAssetsFileHash.FileHash)" />
 		<_PropertyCacheItems Include="TypeMapKind=$(_TypeMapKind)" />
 		<_PropertyCacheItems Include="AndroidManifestPlaceholders=$(AndroidManifestPlaceholders)" />
 		<_PropertyCacheItems Include="ProjectFullPath=$(MSBuildProjectFullPath)" />
diff --git a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.DesignTime.targets b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.DesignTime.targets
index 00f3f2cfdd5..4569f574869 100644
--- a/src/Xamarin.Android.Build.Tasks/Xamarin.Android.DesignTime.targets
+++ b/src/Xamarin.Android.Build.Tasks/Xamarin.Android.DesignTime.targets
@@ -13,45 +13,50 @@ This file is used by all project types, including binding projects.
 
   <PropertyGroup>
     <_AndroidIntermediateDesignTimeBuildDirectory>$(IntermediateOutputPath)designtime\</_AndroidIntermediateDesignTimeBuildDirectory>
+    <_AndroidIntermediateDesignTimeStampDirectory>$(_AndroidIntermediateDesignTimeBuildDirectory)stamp\</_AndroidIntermediateDesignTimeStampDirectory>
     <_AndroidDesignTimeBuildPropertiesCache>$(_AndroidIntermediateDesignTimeBuildDirectory)build.props</_AndroidDesignTimeBuildPropertiesCache>
     <_AndroidLibraryImportsDesignTimeCache>$(_AndroidIntermediateDesignTimeBuildDirectory)libraryimports.cache</_AndroidLibraryImportsDesignTimeCache>
     <_AndroidLibraryProjectImportsDesignTimeCache>$(_AndroidIntermediateDesignTimeBuildDirectory)libraryprojectimports.cache</_AndroidLibraryProjectImportsDesignTimeCache>
     <_AndroidManagedResourceDesignerFile>$(_AndroidIntermediateDesignTimeBuildDirectory)$(_AndroidResourceDesigner)</_AndroidManagedResourceDesignerFile>
   </PropertyGroup>
 
-  <Target Name="_CreateStampDirectory">
-    <MakeDir
-        Condition=" '$(_AndroidStampDirectory)' != '' And !Exists('$(_AndroidStampDirectory)') "
-        Directories="$(_AndroidStampDirectory)"
-    />
-  </Target>
-
   <Target Name="_SetupMSBuildAllProjects">
     <ItemGroup>
       <_AndroidMSBuildAllProjects Include="$(MSBuildAllProjects)" Exclude="$(MSBuildProjectFullPath).user" />
     </ItemGroup>
   </Target>
 
-  <Target Name="_SetupDesignTimeBuildForBuild" DependsOnTargets="_CreateStampDirectory">
+  <Target Name="_SetupDesignTimeBuildForBuild">
     <PropertyGroup>
       <DesignTimeBuild Condition=" '$(DesignTimeBuild)' == '' ">false</DesignTimeBuild>
     </PropertyGroup>
+    <MakeDir
+        Condition=" '$(_AndroidStampDirectory)' != '' And !Exists('$(_AndroidStampDirectory)') "
+        Directories="$(_AndroidStampDirectory)"
+    />
   </Target>
 
-  <Target Name="_SetupDesignTimeBuildForCompile" DependsOnTargets="_CreateStampDirectory">
+  <Target Name="_SetupDesignTimeBuildForCompile">
     <PropertyGroup>
       <DesignTimeBuild Condition=" '$(DesignTimeBuild)' == '' ">true</DesignTimeBuild>
       <ManagedDesignTimeBuild Condition=" '$(AndroidGenerateResourceDesigner)' == 'True' And '$(AndroidUseManagedDesignTimeResourceGenerator)' == 'true' And '$(DesignTimeBuild)' == 'true' And '$(BuildingInsideVisualStudio)' == 'true' ">true</ManagedDesignTimeBuild>
       <ManagedDesignTimeBuild Condition=" '$(ManagedDesignTimeBuild)' == '' And '$(DesignTimeBuild)' == 'True' And '$(AndroidUseDesignerAssembly)' == 'True' " >True</ManagedDesignTimeBuild>
       <ManagedDesignTimeBuild Condition=" '$(ManagedDesignTimeBuild)' == '' ">False</ManagedDesignTimeBuild>
+      <_AndroidStampDirectory Condition=" '$(DesignTimeBuild)' == 'true' ">$(_AndroidIntermediateDesignTimeStampDirectory)</_AndroidStampDirectory>
       <_AndroidLibraryImportsCache Condition=" '$(DesignTimeBuild)' == 'true' And !Exists ('$(_AndroidLibraryImportsCache)') ">$(_AndroidLibraryImportsDesignTimeCache)</_AndroidLibraryImportsCache>
       <_AndroidLibraryProjectImportsCache Condition=" '$(DesignTimeBuild)' == 'true' And !Exists ('$(_AndroidLibraryProjectImportsCache)') ">$(_AndroidLibraryProjectImportsDesignTimeCache)</_AndroidLibraryProjectImportsCache>
       <_AndroidBuildPropertiesCache Condition=" '$(DesignTimeBuild)' == 'true' ">$(_AndroidDesignTimeBuildPropertiesCache)</_AndroidBuildPropertiesCache>
+      <_GeneratorStampFile Condition=" '$(DesignTimeBuild)' == 'true' And !Exists('$(_GeneratorStampFile)') ">$(_AndroidIntermediateDesignTimeStampDirectory)generator.stamp</_GeneratorStampFile>
+      <_AndroidResgenFlagFile Condition=" '$(DesignTimeBuild)' == 'true' And !Exists('$(_AndroidResgenFlagFile)') ">$(_AndroidIntermediateDesignTimeBuildDirectory)R.cs.flag</_AndroidResgenFlagFile>
     </PropertyGroup>
     <MakeDir
         Condition=" '$(_AndroidIsBindingProject)' != 'true' And !Exists ('$(_AndroidIntermediateDesignTimeBuildDirectory)') "
         Directories="$(_AndroidIntermediateDesignTimeBuildDirectory)"
     />
+    <MakeDir
+        Condition=" '$(_AndroidStampDirectory)' != '' And !Exists('$(_AndroidStampDirectory)') "
+        Directories="$(_AndroidStampDirectory)"
+    />
   </Target>
 
 </Project>