Display an error message when the Web request to the Translator service fails.

MetadataTranslator/Metadata Translator/Resources/StringDictionary.xaml

@@ -32,6 +32,8 @@
     <system:String x:Key="TranslatorLocationPrompt">This is typically the Global region, but could also be a single Azure region.</system:String>
     <system:String x:Key="NothingToTranslate">Please select at least one language before you translate the metadata.</system:String>
     <system:String x:Key="UnableToTranslate">Microsoft Translator was unable to translate the metadata strings into {0}. Please try again later or remove this language from the translation.</system:String>
+    <system:String x:Key="UnableToAccessTranslatorEndpoint">Microsoft Translator was unable to translate the metadata strings because of a Web request error. Make sure the Microsoft Translator configuration settings are correct and check your network connection.</system:String>
+    <system:String x:Key="WebRequestError">Web Request Error</system:String>
     <system:String x:Key="ExportHeading">Export .csv files</system:String>
     <system:String x:Key="ExportDescription">You can export the metadata captions, descriptions, and display folder strings into .csv files based on the locale identifiers (LCIDs) of the selected languages. Metadata Translator creates a separate .csv file for each LCID.</system:String>
     <system:String x:Key="ExportFolderDescription">Select the folder where you want to store your .csv files. Note that Metadata Translator might overwrite any existing files in this folder.</system:String>

MetadataTranslator/Metadata Translator/Translations/TranslatorService.cs

@@ -7,6 +7,7 @@ using System.Net.Http;
 using System.Text;
 using System.Threading.Tasks;
 using System.Web.Script.Serialization;
+using System.Windows;
 
 namespace Metadata_Translator
 {
@@ -111,6 +112,8 @@ namespace Metadata_Translator
             /// Translate the batch and assign the translated strings to the target languages.
             /// 
             var translatedStrings = TranslateBatch(translationBatch, translationId);
+            if (translatedStrings.Count > 0)
+            {
                 for (int i = 0; i < maxBatchSize; i++)
                 {
                     foreach (Language language in targetLanguages)
@@ -121,6 +124,7 @@ namespace Metadata_Translator
 
                 Translate(dataRows, targetLanguages, translationId, replaceExistingTranslations, ++iterationId);
             }
+        }
 
         private List<string> TranslateBatch(List<object> sourceObjects, string targetLanguage)
         {
@@ -143,6 +147,18 @@ namespace Metadata_Translator
                 HttpResponseMessage response = client.SendAsync(request).Result;
                 string result = response.Content.ReadAsStringAsync().Result;
 
+                /// Display an error message if the Web request was not successful.
+                /// 
+                if (!response.IsSuccessStatusCode)
+                {
+                    MessageBox.Show(
+                        Application.Current.FindResource("UnableToAccessTranslatorEndpoint") as string, 
+                        Application.Current.FindResource("WebRequestError") as string, 
+                        MessageBoxButton.OK);
+                }
+                else
+                {
+
                     /// Parse the results and add the strings to the translated phrases if there was no error,
                     /// i.e. the target language was returned together with the translated string, which is 
                     /// not the case if the service gives back an error message.
@@ -156,6 +172,7 @@ namespace Metadata_Translator
                         }
                     }
                 }
+            }
 
             return translatedPhrases;
         }