diff --git a/.vscode/launch.json b/.vscode/launch.json
new file mode 100644
index 0000000000..396e7edb12
--- /dev/null
+++ b/.vscode/launch.json
@@ -0,0 +1,11 @@
+{
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": ".NET Core Attach",
+      "type": "coreclr",
+      "request": "attach",
+      "processId": "${command:pickProcess}"
+    }
+  ]
+}
diff --git a/build/RepositoryBuild.targets b/build/RepositoryBuild.targets
index 4ff447a430..2f92b51d9a 100644
--- a/build/RepositoryBuild.targets
+++ b/build/RepositoryBuild.targets
@@ -18,8 +18,6 @@
     </PropertyGroup>
 
     <ItemGroup>
-      <PinPackageSources Include="$(BuildDir)" />
-      <PinPackageSources Include="$(_DependencyPackagesDirectory)" Condition="Exists('$(_DependencyPackagesDirectory)')" />
       <PinnedArtifactInfo Include="@(ArtifactInfo)" Condition="'$(BuildGraphOf)' == ''" />
     </ItemGroup>
 
@@ -35,7 +33,6 @@
       Artifacts="@(PinnedArtifactInfo)"
       Repository="%(RepositoryBuildOrder.Identity)"
       OutputPath="%(RepositoryBuildOrder.RepositoryPath)\build\dependencies.g.targets"
-      RestoreAdditionalSources="@(PinPackageSources)"
       UseFloatingVersions="false"
       Condition="'%(RepositoryBuildOrder.RepositoryPath)' != ''"
       BuildNumber="$(BuildNumber)" />
@@ -51,6 +48,7 @@
   <Target Name="_BuildRepository">
     <PropertyGroup>
       <!-- If there are duplicate properties, the properties which are defined later in the order would override the earlier ones -->
+      <RepositoryBuildArguments>$(RepositoryBuildArguments) /p:DotNetRestoreSourcePropsPath=$(GeneratedRestoreSourcesPropsPath)</RepositoryBuildArguments>
       <RepositoryBuildArguments>$(RepositoryBuildArguments) /p:DotNetPackageVersionPropsPath=$(GeneratedPackageVersionPropsPath)</RepositoryBuildArguments>
       <RepositoryBuildArguments>$(RepositoryBuildArguments) /p:BuildNumber=$(BuildNumber) /p:Configuration=$(Configuration) /p:CommitHash=$(CommitHash)</RepositoryBuildArguments>
       <RepositoryBuildArguments>$(RepositoryBuildArguments) /noconsolelogger '/l:RepoTasks.FlowLogger,$(MSBuildThisFileDirectory)tasks\bin\publish\RepoTasks.dll;Summary;FlowId=$(RepositoryToBuild)'</RepositoryBuildArguments>
diff --git a/build/repo.targets b/build/repo.targets
index 989af75856..fde013f088 100644
--- a/build/repo.targets
+++ b/build/repo.targets
@@ -20,10 +20,10 @@
     <!-- For external packages that come from feeds we don't mirror. -->
     <IntermediateExternalPackageDir>$(IntermediateDir)ext\</IntermediateExternalPackageDir>
     <GeneratedPackageVersionPropsPath>$(IntermediateDir)dependencies.props</GeneratedPackageVersionPropsPath>
+    <GeneratedRestoreSourcesPropsPath>$(IntermediateDir)sources.props</GeneratedRestoreSourcesPropsPath>
     <TcVcsIdPrefix>Patch20_</TcVcsIdPrefix>
 
-    <PrepareDependsOn>$(PrepareDependsOn);CleanArtifacts;CleanUniverseArtifacts</PrepareDependsOn>
-    <CleanDependsOn>$(CleanDependsOn);CleanUniverseArtifacts</CleanDependsOn>
+    <CleanDependsOn>$(CleanDependsOn);CleanArtifacts;CleanUniverseArtifacts</CleanDependsOn>
     <RestoreDependsOn>$(RestoreDependsOn);RestoreExternalDependencies</RestoreDependsOn>
     <CompileDependsOn>$(CompileDependsOn);CloneRepositories;BuildRepositories</CompileDependsOn>
     <PackageDependsOn>$(PackageDependsOn);SplitPackages</PackageDependsOn>
@@ -42,17 +42,27 @@
       DestinationFolder="$(IntermediateMirrorPackageDir)" />
   </Target>
 
-  <Target Name="GeneratePackageVersionPropsFile" DependsOnTargets="ResolveRepoInfo">
+  <Target Name="GeneratePropsFiles" DependsOnTargets="ResolveRepoInfo">
     <ItemGroup>
       <_LineupPackages Include="@(ExternalDependency)" />
       <_LineupPackages Include="%(ArtifactInfo.PackageId)" Version="%(ArtifactInfo.Version)" Condition=" '%(ArtifactInfo.ArtifactType)' == 'NuGetPackage' " />
       <_LineupPackages Include="%(ShippedArtifactInfo.PackageId)" Version="%(ShippedArtifactInfo.Version)" Condition=" '%(ShippedArtifactInfo.ArtifactType)' == 'NuGetPackage' " />
+
+      <_LineupSources Include="$(_DependencyPackagesDirectory)" Condition="'$(_DependencyPackagesDirectory)' != '' AND Exists('$(_DependencyPackagesDirectory)')" />
+      <_LineupSources Include="$(BuildDir)" />
+      <_LineupSources Include="$(IntermediateExternalPackageDir)" />
+      <_LineupSources Include="$(IntermediateMirrorPackageDir)" />
     </ItemGroup>
+
     <RepoTasks.GeneratePackageVersionPropsFile
       Packages="@(_LineupPackages)"
       OutputPath="$(GeneratedPackageVersionPropsPath)" />
 
     <Copy SourceFiles="$(GeneratedPackageVersionPropsPath)" DestinationFolder="$(ArtifactsDir)" />
+
+    <RepoTasks.GenerateRestoreSourcesPropsFile
+      Sources="@(_LineupSources)"
+      OutputPath="$(GeneratedRestoreSourcesPropsPath)" />
   </Target>
 
   <Target Name="CleanUniverseArtifacts">
@@ -140,7 +150,7 @@
   </Target>
 
   <Target Name="BuildRepositories"
-     DependsOnTargets="_PrepareRepositories;_CreateRepositoriesListWithCommits;GeneratePackageVersionPropsFile;ComputeGraph;_BuildRepositories" />
+     DependsOnTargets="_PrepareRepositories;_CreateRepositoriesListWithCommits;GeneratePropsFiles;ComputeGraph;_BuildRepositories" />
 
   <Target Name="ResolveRepoInfo" DependsOnTargets="_PrepareRepositories">
     <MSBuild Projects="$(MSBuildProjectFullPath)"
@@ -183,14 +193,14 @@
     <Error Text="No solutions were found in '$(_CloneRepositoryRoot)'" Condition="@(Solution->Count()) == 0" />
   </Target>
 
-  <Target Name="ComputeGraph" DependsOnTargets="ResolveRepoInfo;GeneratePackageVersionPropsFile">
+  <Target Name="ComputeGraph" DependsOnTargets="ResolveRepoInfo;GeneratePropsFiles">
     <RepoTasks.AnalyzeBuildGraph
       Solutions="@(Solution)"
       Artifacts="@(ArtifactInfo)"
       Dependencies="@(ExternalDependency)"
       ShippedArtifacts="@(ShippedArtifactInfo)"
       StartGraphAt="$(BuildGraphOf)"
-      Properties="Configuration=$(Configuration);BuildNumber=$(BuildNumber);DotNetPackageVersionPropsPath=$(GeneratedPackageVersionPropsPath)">
+      Properties="Configuration=$(Configuration);BuildNumber=$(BuildNumber);DotNetPackageVersionPropsPath=$(GeneratedPackageVersionPropsPath);DotNetRestoreSourcePropsPath=$(GeneratedRestoreSourcesPropsPath)">
       <Output TaskParameter="RepositoryBuildOrder" ItemName="RepositoryBuildOrder" />
     </RepoTasks.AnalyzeBuildGraph>
   </Target>
diff --git a/build/tasks/GenerateLineup.cs b/build/tasks/GenerateLineup.cs
index d1114814b5..5053ebdfa2 100644
--- a/build/tasks/GenerateLineup.cs
+++ b/build/tasks/GenerateLineup.cs
@@ -25,9 +25,6 @@ namespace RepoTasks
         // Can be set to filter the lists of packages when produce a list for a specific repository
         public string Repository { get; set; }
 
-        // Items to add to the RestoreAdditionalProjectSources list in project
-        public ITaskItem[] RestoreAdditionalSources { get; set; }
-
         public bool UseFloatingVersions { get; set; }
 
         public string BuildNumber { get; set; }
@@ -43,16 +40,9 @@ namespace RepoTasks
             }
 
             var items = new XElement("ItemGroup");
-            var props = new XElement("PropertyGroup");
-            var root = new XElement("Project", props, items);
+            var root = new XElement("Project", items);
             var doc = new XDocument(root);
 
-            if (RestoreAdditionalSources?.Length > 0)
-            {
-                var sources = RestoreAdditionalSources.Aggregate("$(RestoreAdditionalProjectSources)", (sum, piece) => sum + ";" + piece.ItemSpec);
-                props.Add(new XElement("RestoreAdditionalProjectSources", sources));
-            }
-
             var packages = new List<PackageInfo>();
 
             foreach (var pkg in Artifacts.Select(ArtifactInfo.Parse)
diff --git a/build/tasks/GenerateRestoreSourcesPropsFile.cs b/build/tasks/GenerateRestoreSourcesPropsFile.cs
new file mode 100644
index 0000000000..75343a16bc
--- /dev/null
+++ b/build/tasks/GenerateRestoreSourcesPropsFile.cs
@@ -0,0 +1,52 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Linq;
+using System.IO;
+using System.Text;
+using System.Xml;
+using System.Xml.Linq;
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+
+namespace RepoTasks
+{
+    public class GenerateRestoreSourcesPropsFile : Task
+    {
+        [Required]
+        public ITaskItem[] Sources { get; set; }
+
+        [Required]
+        public string OutputPath { get; set; }
+
+        public override bool Execute()
+        {
+            OutputPath = OutputPath.Replace('\\', '/');
+            Directory.CreateDirectory(Path.GetDirectoryName(OutputPath));
+
+            var sources = new XElement("DotNetRestoreSources");
+            var doc = new XDocument(new XElement("Project", new XElement("PropertyGroup", sources)));
+
+            var sb = new StringBuilder();
+
+            foreach (var source in Sources)
+            {
+                sb.Append(source.ItemSpec).AppendLine(";");
+            }
+
+            sources.SetValue(sb.ToString());
+
+            var settings = new XmlWriterSettings
+            {
+                OmitXmlDeclaration = true,
+            };
+            using (var writer = XmlWriter.Create(OutputPath, settings))
+            {
+                Log.LogMessage(MessageImportance.High, $"Generate {OutputPath}");
+                doc.Save(writer);
+            }
+            return !Log.HasLoggedErrors;
+        }
+    }
+}
diff --git a/build/tasks/RepoTasks.tasks b/build/tasks/RepoTasks.tasks
index da9cb26603..4990d23c33 100644
--- a/build/tasks/RepoTasks.tasks
+++ b/build/tasks/RepoTasks.tasks
@@ -8,5 +8,6 @@
   <UsingTask TaskName="RepoTasks.DownloadNuGetPackages" AssemblyFile="$(_RepoTaskAssembly)" />
   <UsingTask TaskName="RepoTasks.GenerateLineup" AssemblyFile="$(_RepoTaskAssembly)" />
   <UsingTask TaskName="RepoTasks.GeneratePackageVersionPropsFile" AssemblyFile="$(_RepoTaskAssembly)" />
+  <UsingTask TaskName="RepoTasks.GenerateRestoreSourcesPropsFile" AssemblyFile="$(_RepoTaskAssembly)" />
   <UsingTask TaskName="RepoTasks.VerifyCoherentVersions" AssemblyFile="$(_RepoTaskAssembly)" />
 </Project>