Enable the self diagnostics and fix a NullReferenceException bug

BASE/Test/Microsoft.ApplicationInsights.Test/Microsoft.ApplicationInsights.Tests/Extensibility/Implementation/Tracing/SelfDiagnostics/SelfDiagnosticsEventListenerTest.cs

@@ -84,6 +84,15 @@ public void SelfDiagnosticsEventListener_DateTimeGetBytes()
             CollectionAssert.AreEqual(expected, results);
         }
 
+        [TestMethod]
+        public void SelfDiagnosticsEventListener_EncodeInBuffer_Null()
+        {
+            byte[] buffer = new byte[20];
+            int startPos = 0;
+            int endPos = SelfDiagnosticsEventListener.EncodeInBuffer(null, false, buffer, startPos);
+            Assert.AreEqual(startPos, endPos);
+        }
+
         [TestMethod]
         public void SelfDiagnosticsEventListener_EncodeInBuffer_Empty()
         {

BASE/src/Microsoft.ApplicationInsights/Extensibility/Implementation/Tracing/SelfDiagnostics/SelfDiagnosticsEventListener.cs

@@ -71,6 +71,11 @@ public override void Dispose()
         /// <returns>The position of the buffer after the last byte of the resulting sequence.</returns>
         internal static int EncodeInBuffer(string str, bool isParameter, byte[] buffer, int position)
         {
+            if (str == null)
+            {
+                return position;
+            }
+
             int charCount = str.Length;
             int ellipses = isParameter ? "{...}\n".Length : "...\n".Length;
 

BASE/src/Microsoft.ApplicationInsights/Extensibility/Implementation/Tracing/SelfDiagnostics/SelfDiagnosticsInitializer.cs

@@ -15,7 +15,7 @@ internal class SelfDiagnosticsInitializer : IDisposable
 
         // Long-living object that holds a refresher which checks whether the configuration file was updated
         // every 10 seconds.
-        // private readonly SelfDiagnosticsConfigRefresher configRefresher;
+        private readonly SelfDiagnosticsConfigRefresher configRefresher;
 
         static SelfDiagnosticsInitializer()
         {
@@ -27,7 +27,7 @@ static SelfDiagnosticsInitializer()
 
         private SelfDiagnosticsInitializer()
         {
-            // this.configRefresher = new SelfDiagnosticsConfigRefresher();
+            this.configRefresher = new SelfDiagnosticsConfigRefresher();
         }
 
         /// <summary>
@@ -54,7 +54,7 @@ protected virtual void Dispose(bool disposing)
         {
             if (disposing)
             {
-                // this.configRefresher.Dispose();
+                this.configRefresher.Dispose();
             }
         }
     }