Add null check in examples

examples/ConfigStoreDemo/Program.cs

@@ -24,6 +24,14 @@ public static IWebHost BuildWebHost(string[] args)
                     // 3. Set up the provider to listen for changes to the background color key-value in Azure App Configuration
 
                     var settings = config.AddJsonFile("appsettings.json").Build();
+
+                    if (string.IsNullOrEmpty(settings["connection_string"]))
+                    {
+                        throw new InvalidOperationException(
+                            "Connection string not found. " +
+                            "Please set the 'connection_string' in appsettings.json.");
+                    }
+
                     config.AddAzureAppConfiguration(options =>
                     {
                         options.Connect(settings["connection_string"])

examples/ConsoleAppWithFailOver/Program.cs

@@ -31,7 +31,10 @@ private static void Configure()
             IConfiguration configuration = builder.Build();
 
             IConfigurationSection endpointsSection = configuration.GetSection("AppConfig:Endpoints");
-            IEnumerable<Uri> endpoints = endpointsSection.GetChildren().Select(endpoint => new Uri(endpoint.Value));
+            IEnumerable<Uri> endpoints = endpointsSection.GetChildren()
+                .Select(endpoint => endpoint.Value)
+                .Where(value => !string.IsNullOrEmpty(value))
+                .Select(value => new Uri(value));
 
             if (endpoints == null || !endpoints.Any())
             {