Retry creating file stream in LockFileFormat

src/Microsoft.Framework.PackageManager/Restore/LockFileFormat.cs

@@ -6,6 +6,7 @@
 using System.IO;
 using System.Linq;
 using System.Runtime.Versioning;
+using System.Threading;
 using Microsoft.Framework.Runtime.DependencyManagement;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
@@ -20,12 +21,40 @@ public class LockFileFormat
 
         public LockFile Read(string filePath)
         {
-            using (var stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read))
+            using (var stream = OpenFileStream(filePath))
             {
                 return Read(stream);
             }
         }
 
+        private static FileStream OpenFileStream(string filePath)
+        {
+            // Retry 3 times before re-throw the exception.
+            // It mitigates the race condition when DTH read lock file while VS is restoring projects.
+
+            int retry = 3;
+            while (true)
+            {
+                try
+                {
+                    return new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
+                }
+                catch (Exception)
+                {
+                    if (retry > 0)
+                    {
+                        retry--;
+                        Thread.Sleep(100);
+                    }
+                    else
+                    {
+                        throw;
+                    }
+                }
+            }
+
+        }
+
         public LockFile Read(Stream stream)
         {
             using (var textReader = new StreamReader(stream))

src/Microsoft.Framework.Runtime/DependencyManagement/LockFileReader.cs

@@ -6,19 +6,20 @@
 using System.IO;
 using System.Linq;
 using System.Runtime.Versioning;
+using System.Threading;
 using Microsoft.Framework.Runtime.Json;
 using NuGet;
 
 namespace Microsoft.Framework.Runtime.DependencyManagement
-{    
+{
     internal class LockFileReader
     {
         public const int Version = -9996;
         public const string LockFileName = "project.lock.json";
 
         public LockFile Read(string filePath)
         {
-            using (var stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read))
+            using (var stream = OpenFileStream(filePath))
             {
                 try
                 {
@@ -34,6 +35,34 @@ public LockFile Read(string filePath)
                 }
             }
         }
+
+        private static FileStream OpenFileStream(string filePath)
+        {
+            // Retry 3 times before re-throw the exception.
+            // It mitigates the race condition when DTH read lock file while VS is restoring projects.
+
+            int retry = 3;
+            while (true)
+            {
+                try
+                {
+                    return new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read);
+                }
+                catch (Exception)
+                {
+                    if (retry > 0)
+                    {
+                        retry--;
+                        Thread.Sleep(100);
+                    }
+                    else
+                    {
+                        throw;
+                    }
+                }
+            }
+
+        }
 
         internal LockFile Read(Stream stream)
         {
@@ -254,7 +283,7 @@ private string ReadString(JsonValue json)
             {
                 return (json as JsonString).Value;
             }
-            else if(json is JsonNull)
+            else if (json is JsonNull)
             {
                 return null;
             }