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@paulmedynski paulmedynski released this 09 Nov 22:02
· 27 commits to main since this release
v8.0.0-preview1
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This first 8.0 preview includes changes since the release/7.1 branch point, 92f220956b07328054701a869f452cade51830c1 (2026-09-15), through b87ca6e7643611ddc3273324de346d09e8ff2c43. Changes already shipped in 7.1.1 are identified below because the branch-cut baseline predates that release.

The driver and its four companion packages use package version 8.0.0-preview1. The family AssemblyVersion changes from 7.0.0.0 to 8.0.0.0; .NET Framework applications should review strong-name binding redirects when upgrading. Native SNI and Microsoft.SqlServer.Server remain independently versioned.

Companion package release notes

Added

Vector float16 support and per-connection version negotiation

What Changed:

  • Added support for SQL Server vector(N, float16), including reader values, parameters, output parameters, column schema, and bulk copy. On modern .NET, use SqlVector<Half>; the existing SqlVector<float> API remains supported. (#4501)
  • Added the Vector Type Support connection-string keyword and SqlConnectionStringBuilder.VectorTypeSupport, of type SqlVectorTypeSupport. Values are Off, V1, and V2; the default is V2.

Who Benefits:

  • Applications storing embeddings can use float16 vectors with smaller element payloads, while choosing the result-type contract independently for each connection.

Impact:

  • Result-type change: when the server negotiates V2, modern .NET returns native SqlVector<Half> values for float16 columns instead of JSON strings. Set Vector Type Support=v1 to preserve float16 JSON-string results, or off to receive all vector columns as text. Different settings use separate connection pools.
  • .NET Framework has no System.Half. Float16 columns remain available as JSON strings or through GetSqlVector<float>, which widens their elements exactly. Prefer the latter when reading many values, to avoid the additional JSON serialization.
  • GetColumnSchema() exposes VectorBaseType and VectorDimensions through the column indexer when native vector metadata is negotiated.
  • SQL Server performs cross-base conversion for native vector parameters and bulk-copy inputs. Typed vectors are not automatically serialized for text destinations; supply JSON strings or an explicit SQL cast instead. Vector TVPs are not added by this change.
  • Float16 requires a server that supports it; enable PREVIEW_FEATURES while the server feature is in preview. See the float16 sample.
var builder = new SqlConnectionStringBuilder(connectionString)
{
    VectorTypeSupport = SqlVectorTypeSupport.V1
};

Opt-in reset of pooled transaction isolation levels

What Changed:

  • Added Switch.Microsoft.Data.SqlClient.EnableTransactionIsolationLevelReset, default false. When enabled, a SqlClient-tracked isolation-level change is reset to READ COMMITTED before pooled reuse when no existing enlistment or active delegated transaction root remains. (#96, #4330)

Who Benefits:

  • Applications that otherwise inherit an isolation level left by a previous user of a pooled connection.

Impact:

  • Enable the switch before opening connections. A necessary reset adds a round trip and uses the remaining open-timeout budget. Known Azure Synapse dedicated SQL pool endpoints are excluded; the default preserves existing behavior.
  • A user-issued SET TRANSACTION ISOLATION LEVEL alone does not mark the connection for this reset. The switch is not general cleanup for arbitrary T-SQL session changes.

Additional TimeOnly write paths (net10.0 only)

What Changed:

  • Added TimeOnly support for SqlBulkCopy DataRow/DataTable sources and SqlParameter values with SqlDbType.Variant, writing SQL time values. (#4604)

Who Benefits:

  • Applications using modern .NET time-only values in bulk-copy and variant workflows.

Impact:

  • These paths no longer require conversion to TimeSpan. This does not add TimeOnly to .NET Framework.

Authentication diagnostics

What Changed:

  • The Azure extension forwards MSAL, allowlisted Azure.Identity, and SqlClient token acquisition events to Microsoft.Data.SqlClient.EventSource using the new AuthenticationTrace keyword (0x2000). (#1846, #4872)

Who Benefits:

  • Support teams can diagnose built-in Entra ID authentication without implementing a custom provider or logging callback.

Impact:

  • Collect authentication events with 0x2000, or authentication plus ordinary trace with 0x2002. On modern .NET:

    dotnet-trace collect --process-id <pid> --providers Microsoft.Data.SqlClient.EventSource:0x2000:5 --rundown false

  • On .NET Framework, use ETW or an in-process EventListener. PII logging remains disabled for extension-owned requests. Correlation is best effort; some Azure.Identity events have an empty connection ID and can originate from application-owned credentials. Treat captures as sensitive operational data.

  • See the Azure extension notes for limitations and the logging sample.

Changed

Breaking change: minimum modern runtime is .NET 10

What Changed:

  • Replaced the net8.0 and net9.0 driver implementation targets with net10.0. .NET Framework 4.6.2 support is retained. (#4779)

Who Benefits:

  • Applications moving to the .NET 10 runtime and dependency servicing band.

Impact:

  • Upgrade modern applications to .NET 10, or remain on a compatible earlier driver. Retained netstandard2.0 reference/unsupported-platform assets do not extend driver runtime support to .NET 8 or .NET 9.

Breaking change: TCP MultiSubnetFailover is enabled by default

What Changed:

  • When omitted from the connection string, MultiSubnetFailover now defaults to true for TCP connections. TransparentNetworkIPResolution defaults to false on .NET Framework. (#4876, #4927)

Who Benefits:

  • Applications connecting to multi-address hosts try resolved IP addresses in parallel, without needing an explicit opt-in.

Impact:

  • Explicit values remain authoritative. The automatic default is disabled for non-TCP protocols, LocalDB, database mirroring partners, admin:/via:, and unprefixed local servers using native SNI. Explicit true still fails with unsupported protocols or failover partners. MSF retains its 64-address limit.
  • With native SNI on Windows, an unprefixed remote host now uses TCP only, without Named Pipes fallback. Use np: or MultiSubnetFailover=false when needed.
  • With MSF enabled, IPAddressPreference and TNIR are ignored. The builder reports the keyword default, not the routing decision for a particular connection.
  • Restore the old MSF default with Switch.Microsoft.Data.SqlClient.EnableMultiSubnetFailoverByDefault=false. On .NET Framework, also set Switch.Microsoft.Data.SqlClient.DisableTNIRByDefaultInConnectionString=false to restore the previous TNIR default. Set switches before using SqlClient. See networking migration guidance.

Breaking change: Azure Attestation requires the Azure extension

What Changed:

  • Moved Azure Attestation token validation and the IdentityModel dependencies from the core driver to Microsoft.Data.SqlClient.Extensions.Azure. (#4017, #4790)

Who Benefits:

  • Applications not using Azure Attestation no longer receive these dependencies from core.

Impact:

  • Applications using Attestation Protocol=AAS must explicitly reference the matching Azure extension. Without it, enclave session setup throws InvalidOperationException.
  • The Azure extension now depends on Azure.Core rather than Azure.Identity. Credential namespaces are unchanged. Remove direct Azure.Identity references older than 1.21.0, or upgrade to 1.21.0 or later; Azure.Identity.Broker users need 1.6.0 or later. (#4749)

Breaking changes: reference API and argument validation corrections

What Changed:

  • Reference APIs now match implementation accessibility and sealing, and no longer expose the nonexistent SqlBatchCommand.CanCreateParameter setter on .NET Framework. (#4832, #4890)
  • SqlParameterCollection.RemoveAt(int) throws ArgumentOutOfRangeException, rather than IndexOutOfRangeException, for an invalid index; indexer behavior is unchanged. (#4874)
  • Character-type SqlMetaData construction in globalization-invariant mode requires an overload with an explicit LCID (net10.0 only). (#4457)

Who Benefits:

  • Consumers get accurate compile-time API contracts and explicit argument validation.

Impact:

  • Correct code that instantiated inaccessible types, derived from sealed data-classification types, or assigned the nonexistent setter. Update exception handling for RemoveAt(int).
  • Use a constructor with locale or localeId for character metadata in invariant mode; this does not add general globalization-invariant connection support.

Package layout and family-version validation

  • Managed driver implementations now reside in lib/net462 and lib/net10.0, without duplicated RID-specific managed DLLs. Update custom scripts copying from runtimes/<rid>/lib/<tfm>/Microsoft.Data.SqlClient.dll. Native SNI remains separate. (#4673)
  • Consumer builds emit warning SQLCLIENT001 for mismatched installed family package versions, including preview suffixes. Use matching driver and companion versions. Native SNI and Microsoft.SqlServer.Server are excluded; setting SqlClientEnforceFamilyVersions=false disables the check. (#4815)
  • Corrected Source Link mappings and package source coverage. This branch-cut delta was also backported to 7.1; it is not unique to 8.0. (#4710)

Windows connection pool identity isolation (Windows only)

  • Pool identity includes the Windows logon session, separating network-only impersonation sessions even when their local SID is identical. Reusing tokens from the same logon session preserves reuse; distinct sessions can increase pool counts. (#4814)
  • See connection pooling and impersonation.

Trimming and authentication configuration

  • Authentication registration/bootstrap now lives in Abstractions, allowing SqlAuthenticationProvider.GetProvider/SetProvider to use the shared registry without loading the driver through reflection. SqlAuthenticationInitializer also lives in Abstractions, with a type forward preserving existing references. Abstractions adds a trim/AOT-analyzed net10.0 asset. (#4821)

  • Switch.Microsoft.Data.SqlClient.EnableAppConfig controls authentication configuration on both .NET Framework and modern .NET. The driver's separate retry-configuration and switch-override readers use this switch on modern .NET only; they remain unchanged on .NET Framework. (#4697, #4821)

  • Added Switch.Microsoft.Data.SqlClient.EnableAzureExtensionDiscovery for reflective authentication-provider discovery. Both authentication switches default to true and cache their first value. Explicit provider registration remains available when discovery is disabled. Authentication discovery does not control the driver's separate Azure Attestation loader.

  • For explicit registration in trimmed/Native AOT applications, disable both reflective paths at publish time, then explicitly construct/register a provider for every required method before opening connections. Runtime switch values alone cannot remove code during publication.

    <ItemGroup>
  <RuntimeHostConfigurationOption Include="Switch.Microsoft.Data.SqlClient.EnableAppConfig"
                                  Value="false" Trim="true" />
  <RuntimeHostConfigurationOption Include="Switch.Microsoft.Data.SqlClient.EnableAzureExtensionDiscovery"
                                  Value="false" Trim="true" />
</ItemGroup>

  • Trimmed JIT applications can retain enabled reflective paths if they preserve the configuration infrastructure, handlers, provider/initializer constructors, and Azure discovery contracts. Enabling a switch does not root these members. Enabled paths report trimming warnings and, for Native AOT, dynamic-code warnings.

  • Source-generated JSON serialization replaces reflection-based calls for vector conversions and enclave attestation, including the asynchronous HGS request path, reducing trimming and dynamic-code warnings (net10.0 only). JSON representations remain unchanged. (#4683, #4801)

  • Reduced trimming/AOT warnings in diagnostics, schema metadata, server discovery, and native interop (net10.0 only). These are incremental improvements, not complete Native AOT support. (#4684, #4688, #4703)

  • Authentication section handlers are public in Abstractions; existing driver-qualified app.config declarations remain supported. Configured providers/initializers take precedence over application registrations, which take precedence over Azure defaults. Failed explicit configuration does not silently select an earlier/default provider; failures are traced, and explicit successful application registration can recover a failed method. Check SetProvider's return value and trace diagnostics when registering. (#4816, #4860, #4821)

Performance and sync/async pathways

  • Reduced allocations in Always Encrypted key handling and cache contention for parallel encryption-key lookups. Calls to key-store providers to decrypt column encryption keys remain serialized. (#4256)
  • Converted asynchronous SqlBulkCopy setup, including metadata retrieval and connection recovery, to native async/await. The per-row asynchronous copy loop is unchanged. (#4687)
  • Added asynchronous enclave-provider and delegate operations, including awaited attestation HTTP requests and retry delays. This is groundwork, not end-to-end nonblocking Always Encrypted command execution: the new operations are not yet wired into the command execution path, and driver key-store resolution remains synchronous for both sync and async commands. (#4541, #4886)

Other changes

  • The user-agent Driver Properties mask now reports configured UseCompatibilityAsyncBehaviour and UseCompatibilityProcessSni values through bits 0x2 and 0x4, respectively. These report configuration before compatibility overrides, not effective behavior; async defaults are unchanged. (#4911)
  • Added diagnostics for database-context mismatches after transparent reconnection, without changing recovery behavior. (#4130)
  • Documentation now explains complete reader consumption for InfoMessage delivery and trailing errors. Read()/ReadAsync() ending a result does not establish batch success: with default behavior, advance through NextResult()/NextResultAsync() until false, including after empty results. Cleanup still suppresses pending nonfatal errors; SingleRow and SingleResult retain their discard semantics. Reader runtime behavior is unchanged. (#4723, #4729)
  • Clarified Prepare incompatibility with optimized parameter binding and SqlBatch command-behavior exceptions. (#4726, #4878)
  • Updated shipping dependencies, including the cryptography servicing fixes. Concrete direct dependency floors are listed below and in the companion notes. (#4848, #4880)
  • Updated Microsoft.Data.SqlClient.SNI and Microsoft.Data.SqlClient.SNI.runtime from 7.1.0 to 8.0.0-preview1.26309.4 (Windows native SNI only). (#5011)

Fixed

  • Malformed PRELOGIN option headers, offsets, lengths, and response sizes now produce a parsing error (InvalidOperationException) during Open/OpenAsync, rather than incidental IndexOutOfRangeException failures. (#4902)
  • Responses missing required row metadata or authentication state now produce a corrupted-stream parsing error and invalidate the connection, rather than causing null-reference failures or falling back to unrelated result metadata. The parsing error is an InvalidOperationException, not a SqlException. (#4941)
  • Managed SNI honors an explicit HostNameInCertificate as the sole expected certificate hostname, rather than accepting a match only to the destination (net10.0, managed SNI only). Certificate-chain and ServerCertificate checks are unchanged. (#4905)
  • Fixed managed-SNI parallel TCP connection attempts failing when one address errors immediately despite another reachable address; unused sockets are disposed (net10.0, managed SNI only). (#4929)
  • Fixed the managed-SNI MARS receive teardown race that could leave an unobserved callback exception during disposal (net10.0, managed SNI only). (#4680)
  • Fixed HasRows returning false when multiple informational messages precede rows. (#4773)
  • Fixed XML streaming failures for fragments beginning with text by explicitly selecting UTF-16LE when creating the XML reader. (#4757)
  • Fixed corrupted nvarchar text from GetTextReader() with SequentialAccess on big-endian platforms; little-endian behavior is unchanged (big-endian only). (#4945)
  • Fixed SqlBulkCopy losing money/smallmoney type identity in sql_variant values. (#4727)
  • Fixed configurable retry logic retrying a command outside its original transaction after the error aborted that transaction. (#4728)
  • Reassert non-ReadCommitted isolation levels when pooled connections reattach to the same ambient transaction with a pending reset. This unconditional correctness fix can add a round trip and is separate from the opt-in reset switch. (#4335)
  • Prevent V1/V2 pool pruning from retiring pools with in-flight acquisition, physical creation, or background replenishment, preserving transaction-affine reuse and avoiding unintended transaction promotion. Explicit clear/shutdown semantics are unchanged. (#4755, #4754)
  • Isolate cached enclave sessions by attestation protocol, server, database, and URL. (#4829)
  • Retry providers load/resolve in SqlClient's current AssemblyLoadContext, rather than the default context (net10.0 only). Collectible contexts using managed SNI can unload; this does not promise native-SNI unloadability. (#4588)
  • Prevent eager native SNI initialization on non-Windows platforms (net10.0 on Linux/macOS). (#4700)
  • Fixed the nullable statistics execution-timer race and active soft-connection counter drift when the default wait-handle pool reclaims abandoned connections. Concurrent use of a connection is still unsupported. (#4875, #4725)
  • Formatter-based SqlException serialization preserves Errors and derived error properties such as Number, addressing .NET Framework remoting scenarios. Formatter serialization remains obsolete on modern .NET; this is not guidance to use BinaryFormatter or deserialize untrusted data. (#1940, #4622)
  • Restored SqlParameterCollection.Add(string, object) and exposed Microsoft.Data.SqlClient.Server.TriggerAction in the reference assembly (net462 only). The former remains obsolete; prefer AddWithValue or explicitly typed parameters. (#4832)
  • Windows WAM missing-parent-window errors now explain alternatives for windowless hosts, preserving the MSAL error code and inner exception (Windows only, Azure extension). (#4858)

Included in the branch-cut delta, already shipped in 7.1.1

  • Fixed zero-valued decimal parameters with equal precision and scale. (#4721)
  • Fixed expired/nearly expired access-token eviction in opt-in connection pool V2. (#4734)
  • Preserve admitted in-flight opens during pool clearing, discarding connections returned to the retired pool. (#4718)

These are retained because the requested baseline predates 7.1.1; they are not new fixes for applications already using that release.

Removed

Breaking change: SQL Server 2005 compatibility

What Changed:

  • Removed SQL Server 2005 connectivity and Type System Version=SQL Server 2005, including its date/time-as-string and large-UDT-as-binary compatibility projections. (#4881)

Impact:

  • SQL Server 2005 connections are rejected. Remove that type-system setting and update code that depended on its projections to consume current date/time and UDT representations.

Contributors

We thank the following public contributors for their contributions to this release:

Target Platform Support

  • .NET Framework 4.6.2+ on Windows.
  • .NET 10.0+ on Windows, Linux, and macOS.
  • netstandard2.0 assets are for reference/unsupported-platform scenarios only.

Dependencies

The following table lists direct dependency floors. Driver-family packages use 8.0.0-preview1; the independently versioned Microsoft.SqlServer.Server dependency is 1.0.0. SNI uses the range [8.0.0-preview1.26309.4, 9.0.0).

Dependency net462 net10.0 netstandard2.0
Microsoft.Bcl.Cryptography 10.0.13 10.0.13 10.0.13
Microsoft.Bcl.TimeProvider 10.0.13 - 10.0.13
Microsoft.Data.SqlClient.Extensions.Abstractions 8.0.0-preview1 8.0.0-preview1 8.0.0-preview1
Microsoft.Data.SqlClient.Internal.Logging 8.0.0-preview1 8.0.0-preview1 8.0.0-preview1
Microsoft.Data.SqlClient.SNI 8.0.0-preview1.26309.4 - -
Microsoft.Data.SqlClient.SNI.runtime - 8.0.0-preview1.26309.4 8.0.0-preview1.26309.4
Microsoft.Extensions.Caching.Memory 10.0.13 10.0.13 10.0.13
Microsoft.SqlServer.Server - 1.0.0 1.0.0
System.Buffers 4.6.1 - -
System.Configuration.ConfigurationManager - 10.0.13 10.0.13
System.Data.Common 4.3.0 - -
System.Diagnostics.DiagnosticSource 10.0.13 - -
System.Memory 4.6.3 - -
System.Runtime.InteropServices.RuntimeInformation 4.3.0 - -
System.Security.Cryptography.Pkcs 10.0.13 10.0.13 10.0.13
System.Text.Json 10.0.13 - 10.0.13
System.Threading.Channels 10.0.13 - 10.0.13
System.Threading.RateLimiting 10.0.13 10.0.13 10.0.13
System.ValueTuple 4.6.2 - -
Assets 7
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