Sync sample changes into snippet doc (#2837)

Author: David-Engel

doc/snippets/Microsoft.Data.SqlClient/SqlAuthenticationProvider.xml

@@ -9,10 +9,12 @@
         The following example demonstrates implementing a custom SqlAuthenticationProvider and providing the same to SqlClient for overriding Device Code Flow authentication mode:
         <code language="c#">
           using System;
+          using System.Collections.Generic;
+          using System.Linq;
           using System.Threading.Tasks;
-          using Microsoft.Identity.Client;
           using Microsoft.Data.SqlClient;
-          
+          using Microsoft.Identity.Client;
+
           namespace CustomAuthenticationProviderExamples
           {
               /// &lt;summary&gt;
@@ -21,35 +23,52 @@
               /// &lt;/summary&gt;
               public class CustomDeviceCodeFlowAzureAuthenticationProvider : SqlAuthenticationProvider
               {
+                  private const string clientId = "my-client-id";
+                  private const string clientName = "My Application Name";
+                  private const string s_defaultScopeSuffix = "/.default";
+
+                  // Maintain a copy of the PublicClientApplication object to cache the underlying access tokens it provides
+                  private static IPublicClientApplication pcApplication;
+
                   public override async Task&lt;SqlAuthenticationToken&gt; AcquireTokenAsync(SqlAuthenticationParameters parameters)
                   {
-                      string clientId = "my-client-id";
-                      string clientName = "My Application Name";
-                      string s_defaultScopeSuffix = "/.default";
-          
                       string[] scopes = new string[] { parameters.Resource.EndsWith(s_defaultScopeSuffix) ? parameters.Resource : parameters.Resource + s_defaultScopeSuffix };
-          
-                      IPublicClientApplication app = PublicClientApplicationBuilder.Create(clientId)
-                          .WithAuthority(parameters.Authority)
-                          .WithClientName(clientName)
-                          .WithRedirectUri("https://login.microsoftonline.com/common/oauth2/nativeclient")
+
+                      IPublicClientApplication app = pcApplication;
+                      if (app == null)
+                      {
+                          pcApplication = app = PublicClientApplicationBuilder.Create(clientId)
+                              .WithAuthority(parameters.Authority)
+                              .WithClientName(clientName)
+                              .WithRedirectUri("https://login.microsoftonline.com/common/oauth2/nativeclient")
                           .Build();
-          
-                      AuthenticationResult result = await app.AcquireTokenWithDeviceCode(scopes,
-                      deviceCodeResult => CustomDeviceFlowCallback(deviceCodeResult)).ExecuteAsync();
+                      }
+
+                      AuthenticationResult result;
+
+                      try
+                      {
+                          IEnumerable&lt;IAccount&gt; accounts = await app.GetAccountsAsync();
+                          result = await app.AcquireTokenSilent(scopes, accounts.FirstOrDefault()).ExecuteAsync();
+                      }
+                      catch (MsalUiRequiredException)
+                      {
+                          result = await app.AcquireTokenWithDeviceCode(scopes,
+                                  deviceCodeResult => CustomDeviceFlowCallback(deviceCodeResult)).ExecuteAsync();
+                      }
+
                       return new SqlAuthenticationToken(result.AccessToken, result.ExpiresOn);
                   }
-          
-                  public override bool IsSupported(SqlAuthenticationMethod authenticationMethod) =>
-                      authenticationMethod.Equals(SqlAuthenticationMethod.ActiveDirectoryDeviceCodeFlow);
-          
-                  private Task CustomDeviceFlowCallback(DeviceCodeResult result)
+
+                  public override bool IsSupported(SqlAuthenticationMethod authenticationMethod) => authenticationMethod.Equals(SqlAuthenticationMethod.ActiveDirectoryDeviceCodeFlow);
+
+                  private static Task&lt;int&gt; CustomDeviceFlowCallback(DeviceCodeResult result)
                   {
                       Console.WriteLine(result.Message);
                       return Task.FromResult(0);
                   }
               }
-          
+
               public class Program
               {
                   public static void Main()