Add actionable error message for missing Azure package when Entra ID auth methods are used

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/Connection/SqlConnectionInternal.cs

@@ -2732,7 +2732,7 @@ private SqlFedAuthToken GetFedAuthToken(SqlFedAuthInfo fedAuthInfo)
             SqlAuthenticationProvider? authProvider = SqlAuthenticationProviderManager.GetProvider(ConnectionOptions.Authentication);
             if (authProvider == null && _accessTokenCallback == null)
             {
-                throw SQL.CannotFindAuthProvider(ConnectionOptions.Authentication.ToString());
+                throw SQL.CannotFindAuthProvider(ConnectionOptions.Authentication);
             }
 
             // We will perform retries if the provider indicates an error that

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlUtil.cs

@@ -511,9 +511,26 @@ internal static Exception UnsupportedAuthenticationByProvider(string authenticat
             return ADP.NotSupported(StringsHelper.GetString(Strings.SQL_UnsupportedAuthenticationByProvider, type, authentication));
         }
 
-        internal static Exception CannotFindAuthProvider(string authentication)
-        {
-            return ADP.Argument(StringsHelper.GetString(Strings.SQL_CannotFindAuthProvider, authentication));
+        internal static Exception CannotFindAuthProvider(SqlAuthenticationMethod authentication)
+        {
+            string authName = authentication.ToString();
+
+            return authentication switch
+            {
+#pragma warning disable 0618
+                SqlAuthenticationMethod.ActiveDirectoryPassword or
+#pragma warning restore 0618
+                SqlAuthenticationMethod.ActiveDirectoryIntegrated or
+                SqlAuthenticationMethod.ActiveDirectoryInteractive or
+                SqlAuthenticationMethod.ActiveDirectoryServicePrincipal or
+                SqlAuthenticationMethod.ActiveDirectoryDeviceCodeFlow or
+                SqlAuthenticationMethod.ActiveDirectoryManagedIdentity or
+                SqlAuthenticationMethod.ActiveDirectoryMSI or
+                SqlAuthenticationMethod.ActiveDirectoryDefault or
+                SqlAuthenticationMethod.ActiveDirectoryWorkloadIdentity
+                    => ADP.Argument(StringsHelper.GetString(Strings.SQL_CannotFindActiveDirectoryAuthProvider, authName)),
+                _ => ADP.Argument(StringsHelper.GetString(Strings.SQL_CannotFindAuthProvider, authName)),
+            };
         }
 
         internal static Exception ParameterCannotBeEmpty(string paramName)

src/Microsoft.Data.SqlClient/src/Resources/Strings.resx

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <root>
   <!--
     Microsoft ResX Schema
@@ -2583,6 +2583,9 @@
   <data name="SQL_CannotFindAuthProvider" xml:space="preserve">
     <value>Cannot find an authentication provider for '{0}'.</value>
   </data>
+  <data name="SQL_CannotFindActiveDirectoryAuthProvider" xml:space="preserve">
+    <value>Cannot find an authentication provider for '{0}'. Install the 'Microsoft.Data.SqlClient.Extensions.Azure' NuGet package (https://www.nuget.org/packages/Microsoft.Data.SqlClient.Extensions.Azure) to use Active Directory (Entra ID) authentication methods.</value>
+  </data>
   <data name="SQL_CannotGetAuthProviderConfig" xml:space="preserve">
     <value>Failed to read the config section for authentication providers.</value>
   </data>

src/Microsoft.Data.SqlClient/tests/UnitTests/Microsoft/Data/SqlClient/SqlUtilTests.cs

@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using Xunit;
+
+namespace Microsoft.Data.SqlClient.UnitTests
+{
+    public class SqlUtilTests
+    {
+        [Theory]
+#pragma warning disable 0618
+        [InlineData(SqlAuthenticationMethod.ActiveDirectoryPassword)]
+#pragma warning restore 0618
+        [InlineData(SqlAuthenticationMethod.ActiveDirectoryIntegrated)]
+        [InlineData(SqlAuthenticationMethod.ActiveDirectoryInteractive)]
+        [InlineData(SqlAuthenticationMethod.ActiveDirectoryServicePrincipal)]
+        [InlineData(SqlAuthenticationMethod.ActiveDirectoryDeviceCodeFlow)]
+        [InlineData(SqlAuthenticationMethod.ActiveDirectoryManagedIdentity)]
+        [InlineData(SqlAuthenticationMethod.ActiveDirectoryMSI)]
+        [InlineData(SqlAuthenticationMethod.ActiveDirectoryDefault)]
+        [InlineData(SqlAuthenticationMethod.ActiveDirectoryWorkloadIdentity)]
+        public void CannotFindAuthProvider_ActiveDirectoryMethod_ContainsPackageGuidance(SqlAuthenticationMethod authMethod)
+        {
+            Exception exception = SQL.CannotFindAuthProvider(authMethod);
+
+            Assert.IsType<ArgumentException>(exception);
+            Assert.Contains(authMethod.ToString(), exception.Message);
+            Assert.Contains("Microsoft.Data.SqlClient.Extensions.Azure", exception.Message);
+        }
+
+        [Theory]
+        [InlineData(SqlAuthenticationMethod.NotSpecified)]
+        [InlineData(SqlAuthenticationMethod.SqlPassword)]
+        public void CannotFindAuthProvider_NonActiveDirectoryMethod_DoesNotContainPackageGuidance(SqlAuthenticationMethod authMethod)
+        {
+            Exception exception = SQL.CannotFindAuthProvider(authMethod);
+
+            Assert.IsType<ArgumentException>(exception);
+            Assert.Contains(authMethod.ToString(), exception.Message);
+            Assert.DoesNotContain("Microsoft.Data.SqlClient.Extensions.Azure", exception.Message);
+        }
+    }
+}