Migrate to latest api-version and small fixes (#508)

Author: RupengLiu

src/APIM_ARMTemplate/apimtemplate/Common/Constants/GlobalConstants.cs

@@ -14,7 +14,7 @@ internal static class GlobalConstants
         public const string ExtractName = "extract";
         public const string ExtractDescription = "Extract an existing API Management instance";
 
-        public const string APIVersion = "2019-01-01";
+        public const string APIVersion = "2021-01-01-preview";
         public const string LinkedAPIVersion = "2018-05-01";
         public const int NumOfRecords = 100;
 

src/APIM_ARMTemplate/apimtemplate/Extractor/EntityExtractors/EntityExtractor.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.Net.Http;
+using System;
 using System.Net.Http.Headers;
 using System.Threading.Tasks;
 using Microsoft.Azure.Management.ApiManagement.ArmTemplates.Common;

src/APIM_ARMTemplate/apimtemplate/Extractor/EntityExtractors/PropertyExtractor.cs

@@ -18,8 +18,7 @@ public async Task<string[]> GetPropertiesAsync(string ApiManagementName, string
             do
             {
                 (string azToken, string azSubId) = await auth.GetAccessToken();
-
-                string requestUrl = string.Format("{0}/subscriptions/{1}/resourceGroups/{2}/providers/Microsoft.ApiManagement/service/{3}/properties?$skip={4}&api-version={5}",
+                string requestUrl = string.Format("{0}/subscriptions/{1}/resourceGroups/{2}/providers/Microsoft.ApiManagement/service/{3}/namedValues?$skip={4}&api-version={5}",
                    baseUrl, azSubId, ResourceGroupName, ApiManagementName, numOfProperties, GlobalConstants.APIVersion);
 
                 numOfProperties += GlobalConstants.NumOfRecords;
@@ -42,7 +41,7 @@ public async Task<string> GetPropertyDetailsAsync(string ApiManagementName, stri
         {
             (string azToken, string azSubId) = await auth.GetAccessToken();
 
-            string requestUrl = string.Format("{0}/subscriptions/{1}/resourceGroups/{2}/providers/Microsoft.ApiManagement/service/{3}/properties/{4}?api-version={5}",
+            string requestUrl = string.Format("{0}/subscriptions/{1}/resourceGroups/{2}/providers/Microsoft.ApiManagement/service/{3}/namedValues/{4}?api-version={5}",
                baseUrl, azSubId, ResourceGroupName, ApiManagementName, propertyName, GlobalConstants.APIVersion);
 
             return await CallApiManagementAsync(azToken, requestUrl);