Feature | Add enhanced routing env change support.

[mdaigle]

Ports #3646 to main

[Copilot]

Pull request overview

This pull request ports enhanced routing support from a preview branch to main (originally from PR #3646). Enhanced routing is a TDS protocol extension that allows SQL Server to route connections to an alternate server and specify the target database, extending the existing routing feature which only provided server and port information.

Changes:

• Adds TDS protocol support for enhanced routing ENVCHANGE token (type 21) alongside legacy routing (type 20)
• Implements feature extension negotiation for enhanced routing support between client and server
• Extends test infrastructure (simulated TDS server) to support enhanced routing scenarios
• Adds validation logic and error messages for enhanced routing information

Reviewed changes

Copilot reviewed 21 out of 22 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
TDS/TDS.csproj	Removes explicit file list, relying on SDK-style auto-discovery
TdsEnhancedRoutingEnvChangeTokenValue.cs	New class for parsing enhanced routing token with database name
TDSEnvChangeTokenType.cs	Adds EnhancedRouting enum value (21)
TDSEnvChangeToken.cs	Adds inflation/deflation for enhanced routing token
RoutingTdsServerArguments.cs	Adds RoutingDatabaseName property to control test behavior
RoutingTdsServer.cs	Refactors to use RoutingDatabaseName to decide legacy vs enhanced routing
FeatureExtensionBehavior.cs	Renames enum from FeatureExtensionEnablementTriState for clarity
GenericTdsServerSession.cs	Renames property to IsEnhancedRoutingSupportRequested
GenericTdsServer.cs	Updates to use renamed FeatureExtensionBehavior and simplifies ack logic
ITDSServerSession.cs	Updates interface property name to IsEnhancedRoutingSupportRequested
TdsServerFixture.cs	Extracts shared test fixture for TdsServer lifecycle management
FeatureExtensionNegotiationTests.cs	Uses shared TdsServerFixture, updates to new enum name
ConnectionEnhancedRoutingTests.cs	New test class verifying enhanced routing scenarios (sync/async/ignored/rejected)
Strings.resx / Strings.Designer.cs	Adds SQLROR_InvalidEnhancedRoutingInfo error message
TdsParserHelperClasses.cs	Extends RoutingInfo with optional DatabaseName property
TdsParser.cs	Implements TryProcessEnhancedRoutingToken to parse enhanced routing ENVCHANGE
TdsEnums.cs	Adds ENV_ENHANCEDROUTING constant (21), removes unused EnvChangeType enum
SqlUtil.cs	Adds ROR_InvalidEnhancedRoutingInfo exception factory method
SqlConnectionInternal.cs	Handles ENV_ENHANCEDROUTING in OnEnvChange, validates enhanced routing info, converts fields to auto-properties
ServerInfo.cs	Uses RoutingInfo.DatabaseName when available, falls back to InitialCatalog

Files not reviewed (1)

• src/Microsoft.Data.SqlClient/src/Resources/Strings.Designer.cs: Language not supported

Comments suppressed due to low confidence (2)

src/Microsoft.Data.SqlClient/tests/UnitTests/SimulatedServerTests/FeatureExtensionNegotiationTests.cs:47

• The comment incorrectly states "UserAgent FE token" but should reference "EnhancedRoutingSupport FE token" since the test is verifying enhanced routing support, not user agent functionality.

            // Test should fail if no UserAgent FE token is found

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TdsServerArguments.cs:31

• This TODO comment was added without sufficient context or a tracking issue reference. Please either provide more context (e.g., "TODO: change this to expect ITestOutputHelper for better test output integration with xUnit") or remove it if not actionable. If this is tracking work for a future improvement, consider creating a GitHub issue and referencing it in the TODO.

        /// TODO: change this to expect ITestOutputHelper?

[mdaigle]

Following the format of other trace messages in this file. As a separate piece of work, the messages should be edited up to better match the file name.