Enable User Agent feature extension

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/LocalAppContextSwitches.cs

@@ -36,13 +36,6 @@ internal static class LocalAppContextSwitches
     private const string EnableMultiSubnetFailoverByDefaultString =
         "Switch.Microsoft.Data.SqlClient.EnableMultiSubnetFailoverByDefault";
 
-    /// <summary>
-    /// The name of the app context switch that controls whether
-    /// the user agent feature is enabled.
-    /// </summary>
-    private const string EnableUserAgentString =
-        "Switch.Microsoft.Data.SqlClient.EnableUserAgent";
-
     #if NET
     /// <summary>
     /// The name of the app context switch that controls whether
@@ -177,11 +170,6 @@ private enum SwitchValue : byte
     /// </summary>
     private static SwitchValue s_enableMultiSubnetFailoverByDefault = SwitchValue.None;
 
-    /// <summary>
-    /// The cached value of the EnableUserAgent switch.
-    /// </summary>
-    private static SwitchValue s_enableUserAgent = SwitchValue.None;
-
     #if NET
     /// <summary>
     /// The cached value of the GlobalizationInvariantMode switch.
@@ -319,18 +307,6 @@ static LocalAppContextSwitches()
             defaultValue: false,
             ref s_enableMultiSubnetFailoverByDefault);
 
-    /// <summary>
-    /// When set to true, the user agent feature is enabled and the driver will
-    /// send the user agent string to the server.
-    ///
-    /// The default value of this switch is false.
-    /// </summary>
-    public static bool EnableUserAgent =>
-        AcquireAndReturn(
-            EnableUserAgentString,
-            defaultValue: false,
-            ref s_enableUserAgent);
-
     #if NET
     /// <summary>
     /// .NET Core 2.0 and up supports Globalization Invariant mode, which

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParser.cs

@@ -9663,7 +9663,7 @@ private int ApplyFeatureExData(TdsEnums.FeatureExtension requestedFeatures,
                 checked
                 {
                     // NOTE: As part of TDS spec UserAgent feature extension should be the first feature extension in the list.
-                    if (LocalAppContextSwitches.EnableUserAgent && ((requestedFeatures & TdsEnums.FeatureExtension.UserAgent) != 0))
+                    if ((requestedFeatures & TdsEnums.FeatureExtension.UserAgent) != 0)
                     {
                         length += WriteUserAgentFeatureRequest(userAgent, write);
                     }

src/Microsoft.Data.SqlClient/tests/Common/LocalAppContextSwitchesHelper.cs

@@ -43,7 +43,6 @@ public sealed class LocalAppContextSwitchesHelper : IDisposable
     private readonly bool? _disableTnirByDefaultOriginal;
     #endif
     private readonly bool? _enableMultiSubnetFailoverByDefaultOriginal;
-    private readonly bool? _enableUserAgentOriginal;
     #if NET
     private readonly bool? _globalizationInvariantModeOriginal;
     #endif
@@ -93,8 +92,6 @@ public LocalAppContextSwitchesHelper()
             #endif
             _enableMultiSubnetFailoverByDefaultOriginal =
                 GetSwitchValue("s_enableMultiSubnetFailoverByDefault");
-            _enableUserAgentOriginal =
-                GetSwitchValue("s_enableUserAgent");
             #if NET
             _globalizationInvariantModeOriginal =
                 GetSwitchValue("s_globalizationInvariantMode");
@@ -149,9 +146,6 @@ public void Dispose()
             SetSwitchValue(
                 "s_enableMultiSubnetFailoverByDefault",
                 _enableMultiSubnetFailoverByDefaultOriginal);
-            SetSwitchValue(
-                "s_enableUserAgent",
-                _enableUserAgentOriginal);
             #if NET
             SetSwitchValue(
                 "s_globalizationInvariantMode",
@@ -228,15 +222,6 @@ public bool? EnableMultiSubnetFailoverByDefault
         set => SetSwitchValue("s_enableMultiSubnetFailoverByDefault", value);
     }
 
-    /// <summary>
-    /// Get or set the EnableUserAgent switch value.
-    /// </summary>
-    public bool? EnableUserAgent
-    {
-        get => GetSwitchValue("s_enableUserAgent");
-        set => SetSwitchValue("s_enableUserAgent", value);
-    }
-
     #if NET
     /// <summary>
     /// Get or set the GlobalizationInvariantMode switch value.

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

@@ -28,7 +28,6 @@ public void TestDefaultAppContextSwitchValues()
         Assert.False(LocalAppContextSwitches.UseConnectionPoolV2);
         Assert.False(LocalAppContextSwitches.TruncateScaledDecimal);
         Assert.False(LocalAppContextSwitches.IgnoreServerProvidedFailoverPartner);
-        Assert.False(LocalAppContextSwitches.EnableUserAgent);
         Assert.False(LocalAppContextSwitches.EnableMultiSubnetFailoverByDefault);
         #if NET
         Assert.False(LocalAppContextSwitches.GlobalizationInvariantMode);

src/Microsoft.Data.SqlClient/tests/UnitTests/SimulatedServerTests/ConnectionTests.cs

@@ -841,10 +841,6 @@ public void TestConnWithVectorFeatExtVersionNegotiation(bool expectedConnectionR
         [InlineData(false)]
         public void TestConnWithUserAgentFeatureExtension(bool sendAck)
         {
-            // Enable sending the UserAgent if desired.
-            using LocalAppContextSwitchesHelper switchesHelper = new();
-            switchesHelper.EnableUserAgent = true;
-
             // Start the test server.
             using TdsServer server = new();
             server.Start();
@@ -905,55 +901,5 @@ public void TestConnWithUserAgentFeatureExtension(bool sendAck)
 
             // TODO: Confirm the server sent an Ack by reading log message from SqlInternalConnectionTds
         }
-
-        /// <summary>
-        /// Test to verify no UserAgent relevant information is sent when EnableUserAgentField switch is disabled.
-        /// </summary>
-        [Fact]
-        public void TestConnWithoutUserAgentFeatureExtension()
-        {
-            // Disable the client-side UserAgent field entirely
-            using LocalAppContextSwitchesHelper switchesHelper = new();
-            switchesHelper.EnableUserAgent = false;
-
-            using var server = new TdsServer();
-            server.Start();
-
-            // Do not advertise or force the UserAgent feature on the server
-            server.ServerSupportedUserAgentFeatureExtVersion = 0x00; // no support
-            server.EnableUserAgentFeatureExt = false;                // no forced ACK
-
-            bool loginValidated = false;
-            bool userAgentFeatureSeen = false;
-
-            // Inspect the LOGIN7 packet captured by the test server
-            server.OnLogin7Validated = loginToken =>
-            {
-                var featureExtTokens = loginToken.FeatureExt
-                    .OfType<TDSLogin7GenericOptionToken>()
-                    .ToArray();
-
-                // Ensure there is no UserAgentSupport token at all
-                var uaToken = featureExtTokens.FirstOrDefault(t => t.FeatureID == TDSFeatureID.UserAgentSupport);
-                userAgentFeatureSeen = uaToken is not null;
-
-                loginValidated = true;
-            };
-
-            // Connect to the test TDS server with a basic connection string
-            var connStr = new SqlConnectionStringBuilder
-            {
-                DataSource = $"localhost,{server.EndPoint.Port}",
-                Encrypt = SqlConnectionEncryptOption.Optional,
-            }.ConnectionString;
-
-            using var connection = new SqlConnection(connStr);
-            connection.Open();
-
-            // Verify that the connection succeeded and no UserAgent data was sent
-            Assert.Equal(ConnectionState.Open, connection.State);
-            Assert.True(loginValidated, "Expected LOGIN7 to be validated by the test server");
-            Assert.False(userAgentFeatureSeen, "Did not expect a UserAgentSupport feature token in LOGIN7");
-        }
     }
 }