Resolve review comments

Author: cormacpayne

src/ResourceManager/Resources/Commands.Resources/ActiveDirectory/Cmdlets/ActiveDirectoryBaseCmdlet.cs

@@ -51,47 +51,51 @@ private void HandleException(Exception exception)
             ErrorCategory targetErrorCategory = ErrorCategory.NotSpecified;
             var graphEx = exception as GraphErrorException;
 
-            if (graphEx != null)
+            if (graphEx == null)
             {
-                if (graphEx.Body != null && graphEx.Body.Message != null && graphEx.Body.Code != null)
+                throw exception;
+            }
+
+            if (graphEx.Body != null && graphEx.Body.Message != null && graphEx.Body.Code != null)
+            {
+                WriteDebug(String.Format(ProjectResources.GraphException, graphEx.Body.Code, graphEx.Body.Message));
+                targetEx = new Exception(graphEx.Body.Message);
+                targetErrorId = graphEx.Body.Code;
+            }
+            else
+            {
+                if (graphEx.Response != null && graphEx.Response.StatusCode == HttpStatusCode.NotFound)
                 {
-                    WriteDebug(String.Format(ProjectResources.GraphException, graphEx.Body.Code, graphEx.Body.Message));
-                    targetEx = new Exception(graphEx.Body.Message);
-                    targetErrorId = graphEx.Body.Code;
+                    targetErrorCategory = ErrorCategory.InvalidArgument;
                 }
                 else
                 {
-                    if (graphEx.Response != null && graphEx.Response.StatusCode == HttpStatusCode.NotFound)
-                    {
-                        targetErrorCategory = ErrorCategory.InvalidArgument;
-                    }
-                    else
-                    {
-                        targetErrorCategory = ErrorCategory.InvalidOperation;
-                    }
-                    Exception parsedException = ParseResponse(graphEx);
-                    targetEx = parsedException != null ? parsedException : targetEx;
+                    targetErrorCategory = ErrorCategory.InvalidOperation;
                 }
-                var errorRecord = new ErrorRecord(targetEx, targetErrorId, targetErrorCategory, null);
-                WriteError(errorRecord);
-            }
-            else
-            {
-                throw exception;
+
+                Exception parsedException = ParseResponse(graphEx);
+                targetEx = parsedException ?? targetEx;
             }
+
+            var errorRecord = new ErrorRecord(targetEx, targetErrorId, targetErrorCategory, null);
+            WriteError(errorRecord);
         }
 
 
         private Exception ParseResponse(GraphErrorException graphEx)
         {
-            int exceptionMessageIndex = graphEx.Response.Content.IndexOf("\"value\":", StringComparison.CurrentCultureIgnoreCase);
-            if (exceptionMessageIndex > 0)
+            if (graphEx?.Response?.Content != null)
             {
-                string substring = graphEx.Response.Content.Substring(exceptionMessageIndex + 9);
-                // the start index is added 9, so as to remove the delimiter \"value\":\
-                string exceptionDetails = substring.Substring(0, substring.IndexOf("\"}"));
-                return new Exception(exceptionDetails);
+                int exceptionMessageIndex = graphEx.Response.Content.IndexOf("\"value\":", StringComparison.CurrentCultureIgnoreCase);
+                if (exceptionMessageIndex > 0)
+                {
+                    string substring = graphEx.Response.Content.Substring(exceptionMessageIndex + 9);
+                    // the start index is added 9, so as to remove the delimiter \"value\":\
+                    string exceptionDetails = substring.Substring(0, substring.IndexOf("\"}"));
+                    return new Exception(exceptionDetails);
+                }
             }
+
             return null;
         }
 

src/ResourceManager/Resources/Commands.Resources/ActiveDirectory/Models/ActiveDirectoryClient.cs

@@ -95,7 +95,7 @@ public PSADServicePrincipal GetServicePrincipalBySPN(string spn)
             try
             {
                 var odataQuery = new Rest.Azure.OData.ODataQuery<ServicePrincipal>(s => s.ServicePrincipalNames.Contains(spn));
-                servicePrincipal = GraphClient.ServicePrincipals.List(odataQuery.ToString()).FirstOrDefault()?.ToPSADServicePrincipal();
+                servicePrincipal = GraphClient.ServicePrincipals.List(odataQuery.ToString()).First().ToPSADServicePrincipal();
             }
             catch { /* The service principal does not exist, ignore the exception. */ }
 
@@ -149,7 +149,7 @@ public IEnumerable<PSADServicePrincipal> FilterServicePrincipals(ADObjectFilterO
                 if (!string.IsNullOrEmpty(options.SearchString) && options.SearchString.EndsWith("*"))
                 {
                     options.SearchString = options.SearchString.TrimEnd('*');
-                    odataQuery = new Rest.Azure.OData.ODataQuery<ServicePrincipal>(s => s.DisplayName.StartsWith(options.SearchString));
+                    odataQuery = new Rest.Azure.OData.ODataQuery<ServicePrincipal>(s => s.DisplayName != null && s.DisplayName.StartsWith(options.SearchString));
                 }
                 else
                 {
@@ -216,7 +216,7 @@ public IEnumerable<PSADUser> FilterUsers(ADObjectFilterOptions options, ulong fi
                 if (!string.IsNullOrEmpty(options.SearchString) && options.SearchString.EndsWith("*"))
                 {
                     options.SearchString = options.SearchString.TrimEnd('*');
-                    odataQuery = new Rest.Azure.OData.ODataQuery<User>(u => u.DisplayName.StartsWith(options.SearchString));
+                    odataQuery = new Rest.Azure.OData.ODataQuery<User>(u => u.DisplayName != null && u.DisplayName.StartsWith(options.SearchString));
                 }
                 else
                 {