Use gateway hostname from options for connection string flow

iothub/device/src/Authentication/IotHubConnectionCredentials.cs

@@ -27,23 +27,23 @@ internal IotHubConnectionCredentials()
         /// The authentication method that is used. It includes <see cref="ClientAuthenticationWithSharedAccessKeyRefresh"/>, <see cref="ClientAuthenticationWithSharedAccessSignature"/>,
         /// <see cref="ClientAuthenticationWithX509Certificate"/> or <see cref="EdgeModuleAuthenticationWithHsm"/>.
         /// </param>
-        /// <param name="hostName">The fully-qualified DNS host name of IoT hub.</param>
+        /// <param name="iotHubHostName">The fully-qualified DNS host name of IoT hub.</param>
         /// <param name="gatewayHostName">The fully-qualified DNS host name of the gateway (optional).</param>
         /// <returns>A new instance of the <c>IotHubConnectionCredentials</c> class with a populated connection string.</returns>
-        /// <exception cref="ArgumentNullException"><paramref name="hostName"/>, device Id or <paramref name="authenticationMethod"/> is null.</exception>
-        /// <exception cref="ArgumentException"><paramref name="hostName"/> or device Id are an empty string or consist only of white-space characters.</exception>
+        /// <exception cref="ArgumentNullException"><paramref name="iotHubHostName"/>, device Id or <paramref name="authenticationMethod"/> is null.</exception>
+        /// <exception cref="ArgumentException"><paramref name="iotHubHostName"/> or device Id are an empty string or consist only of white-space characters.</exception>
         /// <exception cref="ArgumentException"><see cref="ClientAuthenticationWithX509Certificate.CertificateChain"/> is used over a protocol other than MQTT over TCP or AMQP over TCP.</exception>
         /// <exception cref="FormatException">Neither shared access key, shared access signature or X509 certificates were presented for authentication.</exception>
         /// <exception cref="FormatException">Either shared access key or shared access signature where presented together with X509 certificates for authentication.</exception>
         /// <exception cref="IotHubClientException"><see cref="ClientAuthenticationWithX509Certificate.CertificateChain"/> could not be installed.</exception>
-        public IotHubConnectionCredentials(IAuthenticationMethod authenticationMethod, string hostName, string gatewayHostName = null)
+        public IotHubConnectionCredentials(IAuthenticationMethod authenticationMethod, string iotHubHostName, string gatewayHostName = default)
         {
             Argument.AssertNotNull(authenticationMethod, nameof(authenticationMethod));
-            Argument.AssertNotNullOrWhiteSpace(hostName, nameof(hostName));
+            Argument.AssertNotNullOrWhiteSpace(iotHubHostName, nameof(iotHubHostName));
 
-            IotHubHostName = hostName;
+            IotHubHostName = iotHubHostName;
             GatewayHostName = gatewayHostName;
-            HostName = gatewayHostName ?? hostName;
+            HostName = gatewayHostName ?? iotHubHostName;
 
             AuthenticationMethod = authenticationMethod;
             IotHubConnectionCredentials iotHubConnectionCredentials = this;
@@ -58,20 +58,21 @@ public IotHubConnectionCredentials(IAuthenticationMethod authenticationMethod, s
         /// Creates an instance of this class using a connection string.
         /// </summary>
         /// <param name="iotHubConnectionString">The IoT hub device connection string.</param>
+        /// <param name="gatewayHostName">The fully-qualified DNS host name of the gateway (optional).</param>
         /// <returns>A new instance of this class.</returns>
         /// <exception cref="ArgumentNullException"><paramref name="iotHubConnectionString"/>, IoT hub host name or device Id is null.</exception>
         /// <exception cref="ArgumentException"><paramref name="iotHubConnectionString"/>, IoT hub host name or device Id are an empty string or consist only of white-space characters.</exception>
         /// <exception cref="FormatException">Neither shared access key nor shared access signature were presented for authentication.</exception>
         /// <exception cref="FormatException">Either shared access key or shared access signature where presented together with X509 certificates for authentication.</exception>
-        public IotHubConnectionCredentials(string iotHubConnectionString)
+        public IotHubConnectionCredentials(string iotHubConnectionString, string gatewayHostName = default)
         {
             Argument.AssertNotNullOrWhiteSpace(iotHubConnectionString, nameof(iotHubConnectionString));
 
             // We'll parse the connection string and use that to build an auth method
             IotHubConnectionString parsedConnectionString = IotHubConnectionStringParser.Parse(iotHubConnectionString);
             AuthenticationMethod = GetAuthenticationMethodFromConnectionString(parsedConnectionString);
 
-            PopulatePropertiesFromConnectionString(parsedConnectionString);
+            PopulatePropertiesFromConnectionString(parsedConnectionString, gatewayHostName);
             SetAuthenticationModel();
             SetTokenRefresherIfApplicable();
 
@@ -249,10 +250,10 @@ private static int UpdateHashCode(int hashCode, object field)
                 : hashCode * -1521134295 + field.GetHashCode();
         }
 
-        private void PopulatePropertiesFromConnectionString(IotHubConnectionString iotHubConnectionString)
+        private void PopulatePropertiesFromConnectionString(IotHubConnectionString iotHubConnectionString, string gatewayHostName)
         {
             IotHubHostName = iotHubConnectionString.IotHubHostName;
-            GatewayHostName = iotHubConnectionString.GatewayHostName;
+            GatewayHostName = iotHubConnectionString.GatewayHostName ?? gatewayHostName;
             HostName = GatewayHostName ?? IotHubHostName;
             DeviceId = iotHubConnectionString.DeviceId;
             ModuleId = iotHubConnectionString.ModuleId;

iothub/device/src/IotHubClientOptions.cs

@@ -85,6 +85,10 @@ public IotHubClientOptions(IotHubClientTransportSettings transportSettings)
         /// <para>
         /// It can also be used for other, custom transparent or protocol gateways.
         /// </para>
+        /// <para>
+        /// If the client uses a connection string-based authentication mechanism, and has a gateway hostname specified in the connection string
+        /// then the value set in options will be ignored.
+        /// </para>
         /// </remarks>
         public string GatewayHostName { get; set; }
 

iothub/device/src/IotHubDeviceClient.cs

@@ -37,7 +37,7 @@ public class IotHubDeviceClient : IotHubBaseClient
         /// </code>
         /// </example>
         public IotHubDeviceClient(string connectionString, IotHubClientOptions options = default)
-            : this(new IotHubConnectionCredentials(connectionString), options)
+            : this(new IotHubConnectionCredentials(connectionString, options?.GatewayHostName), options)
         {
         }
 

iothub/device/src/IotHubModuleClient.cs

@@ -48,7 +48,7 @@ public class IotHubModuleClient : IotHubBaseClient
         /// </code>
         /// </example>
         public IotHubModuleClient(string connectionString, IotHubClientOptions options = default)
-            : this(new IotHubConnectionCredentials(connectionString), options, null)
+            : this(new IotHubConnectionCredentials(connectionString, options?.GatewayHostName), options, null)
         {
         }
 

iothub/device/tests/IotHubDeviceClientTests.cs

@@ -22,7 +22,10 @@ public sealed class IotHubDeviceClientTests
         private const string FakeDeviceId = "fake";
         private const string FakeSharedAccessKey = "dGVzdFN0cmluZzE=";
         private const string FakeSharedAccessKeyName = "AllAccessKey";
+        private const string FakeGatewayHostNameOptions = "my-custom-gateway-options";
+        private const string FakeGatewayHostNameCs = "my-custom-gateway-cs";
         private static readonly string s_fakeConnectionString = $"HostName={FakeHostName};SharedAccessKeyName={FakeSharedAccessKeyName};DeviceId={FakeDeviceId};SharedAccessKey={FakeSharedAccessKey}";
+        private static readonly string s_fakeConnectionStringWithGatewayHostName = $"GatewayHostName={FakeGatewayHostNameCs};HostName={FakeHostName};SharedAccessKeyName={FakeSharedAccessKeyName};DeviceId={FakeDeviceId};SharedAccessKey={FakeSharedAccessKey}";
 
         private static readonly IotHubConnectionCredentials s_iotHubConnectionCredentials = new(s_fakeConnectionString);
 
@@ -1630,6 +1633,42 @@ private static void IotHubDeviceClient_InitWithNonHttpTransportAndModelId_DoesNo
             act.Should().NotThrowAsync();
         }
 
+        [TestMethod]
+        public async Task IotHubDeviceClient_CreateFromConnectionString_WithoutWithGatewayHostname_UseIotHubClientOptionsGatewayHostName()
+        {
+            // arrange
+            var clientOptions = new IotHubClientOptions
+            {
+                GatewayHostName = FakeGatewayHostNameOptions,
+            };
+
+            // act
+            await using var deviceClient = new IotHubDeviceClient(s_fakeConnectionString, clientOptions);
+
+            // assert
+            deviceClient.IotHubConnectionCredentials.IotHubHostName.Should().Be(FakeHostName);
+            deviceClient.IotHubConnectionCredentials.GatewayHostName.Should().Be(FakeGatewayHostNameOptions);
+            deviceClient.IotHubConnectionCredentials.HostName.Should().Be(FakeGatewayHostNameOptions);
+        }
+
+        [TestMethod]
+        public async Task IotHubDeviceClient_CreateFromConnectionString_WithGatewayHostname_OverrideIotHubClientOptionsGatewayHostName()
+        {
+            // arrange
+            var clientOptions = new IotHubClientOptions
+            {
+                GatewayHostName = FakeGatewayHostNameOptions,
+            };
+
+            // act
+            await using var deviceClient = new IotHubDeviceClient(s_fakeConnectionStringWithGatewayHostName, clientOptions);
+
+            // assert
+            deviceClient.IotHubConnectionCredentials.IotHubHostName.Should().Be(FakeHostName);
+            deviceClient.IotHubConnectionCredentials.GatewayHostName.Should().Be(FakeGatewayHostNameCs);
+            deviceClient.IotHubConnectionCredentials.HostName.Should().Be(FakeGatewayHostNameCs);
+        }
+
         private class TestDeviceAuthenticationWithTokenRefresh : ClientAuthenticationWithTokenRefresh
         {
             // This authentication method relies on the default sas token time to live and renewal buffer set by the SDK.