Consolidate OS detection to OsConstants

src/Microsoft.Data.SqlClient/src/Microsoft/Data/Common/AdapterUtil.cs

@@ -13,13 +13,13 @@
 using System.IO;
 using System.Runtime.CompilerServices;
 using System.Security;
+using Microsoft.Data.SqlClient;
 using System.Security.Authentication;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Transactions;
 using Microsoft.Data.Common.ConnectionString;
-using Microsoft.Data.SqlClient;
 using Microsoft.Data.SqlClient.Connection;
 using Microsoft.SqlServer.Server;
 using Microsoft.Win32;
@@ -65,22 +65,6 @@ internal static partial class ADP
         /// </summary>
         internal const int MaxBufferAccessTokenExpiry = 600;
 
-        /// <summary>
-        /// This member returns true if the current OS platform is Windows.
-        /// </summary>
-        /// <remarks>
-        /// This is a const on .NET Framework, and a property on .NET Core, because of differing API availability and JIT requirements.
-        /// .NET Framework will perform basic dead branch elimination when a const value is encountered, while .NET Core can trim Windows-specific
-        /// code when published to non-Windows platforms.
-        /// .NET Core's trimming is very limited though, so this must be used inline within methods to throw PlatformNotSupportedException,
-        /// rather than in a throw helper.
-        /// </remarks>
-        #if NETFRAMEWORK
-        public const bool IsWindows = true;
-        #else
-        public static bool IsWindows => OperatingSystem.IsWindows();
-        #endif
-
         #region UDT
 
         #if NETFRAMEWORK
@@ -159,10 +143,10 @@ internal static Timer UnsafeCreateTimer(
                 state,
                 TimeSpan.FromMilliseconds(dueTimeMilliseconds),
                 TimeSpan.FromMilliseconds(periodMilliseconds));
-        
+
         internal static Timer UnsafeCreateTimer(TimerCallback callback, object state, TimeSpan dueTime, TimeSpan period)
         {
-            // Don't capture the current ExecutionContext and its AsyncLocals onto 
+            // Don't capture the current ExecutionContext and its AsyncLocals onto
             // a global timer causing them to live forever
             bool restoreFlow = false;
             try
@@ -184,7 +168,7 @@ internal static Timer UnsafeCreateTimer(TimerCallback callback, object state, Ti
                 }
             }
         }
-            
+
 
 #region COM+ exceptions
         internal static ArgumentException Argument(string error)
@@ -451,7 +435,7 @@ internal static ArgumentOutOfRangeException InvalidCommandBehavior(CommandBehavi
         internal static object LocalMachineRegistryValue(string subkey, string queryvalue)
         {
             #if NET
-            if (!IsWindows)
+            if (OsConstants.IsUnix)
             {
                 // No registry in non-Windows environments
                 return null;
@@ -639,7 +623,7 @@ internal static string BuildMultiPartName(string[] strings)
         {
             StringBuilder bld = new();
             // Assume we want to build a full multi-part name with all parts except trimming separators for
-            // leading empty names (null or empty strings, but not whitespace). Separators in the middle 
+            // leading empty names (null or empty strings, but not whitespace). Separators in the middle
             // should be added, even if the name part is null/empty, to maintain proper location of the parts.
             for (int i = 0; i < strings.Length; i++)
             {
@@ -839,14 +823,14 @@ internal static Version GetAssemblyVersion()
         /// Represents a collection of Azure SQL Server endpoint URLs for various regions and environments.
         /// </summary>
         /// <remarks>This array includes endpoint URLs for Azure SQL in global, Germany, US Government,
-        /// China, and Fabric environments. These endpoints are used to identify and interact with Azure SQL services 
+        /// China, and Fabric environments. These endpoints are used to identify and interact with Azure SQL services
         /// in their respective regions or environments.</remarks>
         internal static readonly List<string> s_azureSqlServerEndpoints = new() { AZURE_SQL,
                                                                         AZURE_SQL_GERMANY,
                                                                         AZURE_SQL_USGOV,
                                                                         AZURE_SQL_CHINA,
                                                                         AZURE_SQL_FABRIC };
-        
+
         /// <summary>
         /// Contains endpoint strings for Azure SQL Server on-demand services.
         /// Each entry is a combination of the ONDEMAND_PREFIX and a specific Azure SQL endpoint string.
@@ -872,9 +856,9 @@ internal static Version GetAssemblyVersion()
         internal static bool IsAzureSynapseOnDemandEndpoint(string dataSource)
         {
             return IsEndpoint(dataSource, s_azureSynapseOnDemandEndpoints)
-                || dataSource.IndexOf(AZURE_SYNAPSE, StringComparison.OrdinalIgnoreCase) >= 0; 
+                || dataSource.IndexOf(AZURE_SYNAPSE, StringComparison.OrdinalIgnoreCase) >= 0;
         }
-        
+
         internal static bool IsAzureSqlServerEndpoint(string dataSource)
         {
             return IsEndpoint(dataSource, s_azureSqlServerEndpoints);
@@ -1088,7 +1072,7 @@ internal enum InternalErrorCode
 
             SqlDependencyObtainProcessDispatcherFailureObjectHandle = 50,
             SqlDependencyProcessDispatcherFailureCreateInstance = 51,
-            
+
             SqlDependencyCommandHashIsNotAssociatedWithNotification = 53,
 
             UnknownTransactionFailure = 60,

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

@@ -562,7 +562,7 @@ public static bool UseManagedNetworking
                 return s_useManagedNetworking == SwitchValue.True;
             }
 
-            if (!OperatingSystem.IsWindows())
+            if (OsConstants.IsUnix)
             {
                 s_useManagedNetworking = SwitchValue.True;
                 return true;

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/OsConstants.cs

@@ -0,0 +1,82 @@
+// 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.Runtime.InteropServices;
+
+namespace Microsoft.Data.SqlClient;
+
+/// <summary>
+/// Provides platform detection flags for OS-specific code paths.
+/// </summary>
+/// <remarks>
+/// These constants are computed at runtime and cached as static readonly fields.  This design
+/// allows the JIT compiler to elide branches in hot paths based on whether the OS flags are known
+/// constants at JIT compilation time.
+/// </remarks>
+internal static class OsConstants
+{
+    /// <summary>
+    /// Gets a value indicating whether the runtime is executing on Windows.
+    /// </summary>
+    internal static readonly bool IsWindows;
+
+    /// <summary>
+    /// Gets a value indicating whether the runtime is executing on Linux.
+    /// </summary>
+    internal static readonly bool IsLinux;
+
+    /// <summary>
+    /// Gets a value indicating whether the runtime is executing on macOS.
+    /// </summary>
+    internal static readonly bool IsMacOS;
+
+#if NET
+    /// <summary>
+    /// Gets a value indicating whether the runtime is executing on FreeBSD.
+    /// </summary>
+    /// <remarks>
+    /// FreeBSD support is only available in .NET 5+ and later. This field will be
+    /// <c>false</c> on .NET Framework or if the runtime does not support FreeBSD detection.
+    /// </remarks>
+    internal static readonly bool IsFreeBSD;
+#endif
+
+    /// <summary>
+    /// Gets a value indicating whether the runtime is executing on a Unix-like operating system.
+    /// </summary>
+    /// <remarks>
+    /// This is <c>true</c> for Linux, macOS, FreeBSD, and other Unix-like platforms.
+    /// It is <c>false</c> only on Windows.
+    /// </remarks>
+    internal static readonly bool IsUnix;
+
+    /// <summary>
+    /// Initializes platform detection flags by querying <see cref="RuntimeInformation"/>.
+    /// </summary>
+    /// <remarks>
+    /// We use a static constructor instead of a module initializer ([ModuleInitializer]) to avoid
+    /// the CA2255 security concern. Module initializers can be problematic because: 1. They run in
+    /// an unpredictable order relative to other initialization code.  2. They run before the app
+    /// initialization sequence, potentially before security policies are set.  3. They can
+    /// complicate debugging and profiling.
+    ///
+    /// Using a static constructor ensures initialization happens in a well-defined, type-safe
+    /// manner that is compatible with the CLR's type loading guarantees.
+    ///
+    /// The trade-off is that the OS flags won't be initialized until the OsConstants type is first
+    /// accessed, which may cause a slight delay in a hot path, but only once.
+    /// </remarks>
+    static OsConstants()
+    {
+        IsWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
+        IsLinux = RuntimeInformation.IsOSPlatform(OSPlatform.Linux);
+        IsMacOS = RuntimeInformation.IsOSPlatform(OSPlatform.OSX);
+#if NET
+        IsFreeBSD = RuntimeInformation.IsOSPlatform(OSPlatform.FreeBSD);
+        IsUnix = IsLinux || IsMacOS || IsFreeBSD;
+#else
+        IsUnix = IsLinux || IsMacOS;
+#endif
+    }
+}

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlColumnEncryptionCertificateStoreProvider.cs

@@ -57,7 +57,7 @@ public class SqlColumnEncryptionCertificateStoreProvider : SqlColumnEncryptionKe
         /// Gets a string array containing valid certificate locations.
         /// </summary>
         private static string[] ValidCertificateLocations =>
-            Environment.OSVersion.Platform == PlatformID.Win32NT
+            OsConstants.IsWindows
                 ? [CertLocationLocalMachine, CertLocationCurrentUser]
                 : [CertLocationCurrentUser];
 
@@ -158,14 +158,13 @@ private static RSA GetCertificatePrivateKeyByPath(string keyPath, bool isSystemO
             }
 
             // Extract the store location where the cert is stored
-            if (storeLocationSpan.IsEmpty
-                && Environment.OSVersion.Platform == PlatformID.Win32NT)
+            if (storeLocationSpan.IsEmpty && OsConstants.IsWindows)
             {
                 // Default to Local Machine on Windows. Non-Windows platforms only support CurrentUser
                 storeLocation = StoreLocation.LocalMachine;
             }
             else if (storeLocationSpan.Equals(CertLocationLocalMachine.AsSpan(), StringComparison.OrdinalIgnoreCase)
-                && Environment.OSVersion.Platform == PlatformID.Win32NT)
+                && OsConstants.IsWindows)
             {
                 storeLocation = StoreLocation.LocalMachine;
             }

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlColumnEncryptionCngProvider.cs

@@ -149,7 +149,7 @@ private static void GetCngProviderAndKeyId(string keyPath, bool isSystemOp, out
         /// <include file='../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlColumnEncryptionCngProvider.xml' path='docs/members[@name="SqlColumnEncryptionCngProvider"]/DecryptColumnEncryptionKey/*' />
         public override byte[] DecryptColumnEncryptionKey(string? masterKeyPath, string? encryptionAlgorithm, byte[]? encryptedColumnEncryptionKey)
         {
-            if (!ADP.IsWindows)
+            if (OsConstants.IsUnix)
             {
                 throw new PlatformNotSupportedException();
             }
@@ -180,7 +180,7 @@ public override byte[] DecryptColumnEncryptionKey(string? masterKeyPath, string?
         /// <include file='../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlColumnEncryptionCngProvider.xml' path='docs/members[@name="SqlColumnEncryptionCngProvider"]/EncryptColumnEncryptionKey/*' />
         public override byte[] EncryptColumnEncryptionKey(string? masterKeyPath, string? encryptionAlgorithm, byte[]? columnEncryptionKey)
         {
-            if (!ADP.IsWindows)
+            if (OsConstants.IsUnix)
             {
                 throw new PlatformNotSupportedException();
             }
@@ -211,15 +211,15 @@ public override byte[] EncryptColumnEncryptionKey(string? masterKeyPath, string?
         /// <include file='../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlColumnEncryptionCngProvider.xml' path='docs/members[@name="SqlColumnEncryptionCngProvider"]/SignColumnMasterKeyMetadata/*' />
         public override byte[] SignColumnMasterKeyMetadata(string? masterKeyPath, bool allowEnclaveComputations)
         {
-            throw ADP.IsWindows
+            throw OsConstants.IsWindows
                 ? new NotSupportedException()
                 : new PlatformNotSupportedException();
         }
 
         /// <include file='../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlColumnEncryptionCngProvider.xml' path='docs/members[@name="SqlColumnEncryptionCngProvider"]/VerifyColumnMasterKeyMetadata/*' />
         public override bool VerifyColumnMasterKeyMetadata(string? masterKeyPath, bool allowEnclaveComputations, byte[]? signature)
         {
-            throw ADP.IsWindows
+            throw OsConstants.IsWindows
                 ? new NotSupportedException()
                 : new PlatformNotSupportedException();
         }

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlColumnEncryptionCspProvider.cs

@@ -151,7 +151,7 @@ private static int GetProviderType(string providerName, string keyPath, bool isS
         /// <include file='../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlColumnEncryptionCspProvider.xml' path='docs/members[@name="SqlColumnEncryptionCspProvider"]/DecryptColumnEncryptionKey/*' />
         public override byte[] DecryptColumnEncryptionKey(string? masterKeyPath, string? encryptionAlgorithm, byte[]? encryptedColumnEncryptionKey)
         {
-            if (!ADP.IsWindows)
+            if (OsConstants.IsUnix)
             {
                 throw new PlatformNotSupportedException();
             }
@@ -182,7 +182,7 @@ public override byte[] DecryptColumnEncryptionKey(string? masterKeyPath, string?
         /// <include file='../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlColumnEncryptionCspProvider.xml' path='docs/members[@name="SqlColumnEncryptionCspProvider"]/EncryptColumnEncryptionKey/*' />
         public override byte[] EncryptColumnEncryptionKey(string? masterKeyPath, string? encryptionAlgorithm, byte[]? columnEncryptionKey)
         {
-            if (!ADP.IsWindows)
+            if (OsConstants.IsUnix)
             {
                 throw new PlatformNotSupportedException();
             }
@@ -213,15 +213,15 @@ public override byte[] EncryptColumnEncryptionKey(string? masterKeyPath, string?
         /// <include file='../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlColumnEncryptionCspProvider.xml' path='docs/members[@name="SqlColumnEncryptionCspProvider"]/SignColumnMasterKeyMetadata/*' />
         public override byte[] SignColumnMasterKeyMetadata(string? masterKeyPath, bool allowEnclaveComputations)
         {
-            throw ADP.IsWindows
+            throw OsConstants.IsWindows
                 ? new NotSupportedException()
                 : new PlatformNotSupportedException();
         }
 
         /// <include file='../../../../../../doc/snippets/Microsoft.Data.SqlClient/SqlColumnEncryptionCspProvider.xml' path='docs/members[@name="SqlColumnEncryptionCspProvider"]/VerifyColumnMasterKeyMetadata/*' />
         public override bool VerifyColumnMasterKeyMetadata(string? masterKeyPath, bool allowEnclaveComputations, byte[]? signature)
         {
-            throw ADP.IsWindows
+            throw OsConstants.IsWindows
                 ? new NotSupportedException()
                 : new PlatformNotSupportedException();
         }

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

@@ -1376,7 +1376,7 @@ internal static Exception LargeCertificatePathLength(int actualLength, int maxLe
 
         internal static Exception NullCertificatePath(string[] validLocations, bool isSystemOp)
         {
-            if (Environment.OSVersion.Platform == PlatformID.Win32NT)
+            if (OsConstants.IsWindows)
             {
                 Debug.Assert(validLocations.Length == 2);
                 if (isSystemOp)
@@ -1428,7 +1428,7 @@ internal static Exception NullCngKeyPath(bool isSystemOp)
 
         internal static Exception InvalidCertificatePath(string actualCertificatePath, string[] validLocations, bool isSystemOp)
         {
-            if (Environment.OSVersion.Platform == PlatformID.Win32NT)
+            if (OsConstants.IsWindows)
             {
                 Debug.Assert(validLocations.Length == 2);
                 if (isSystemOp)
@@ -1564,7 +1564,7 @@ internal static Exception InvalidCngKey(string masterKeyPath, string cngProvider
 
         internal static Exception InvalidCertificateLocation(string certificateLocation, string certificatePath, string[] validLocations, bool isSystemOp)
         {
-            if (Environment.OSVersion.Platform == PlatformID.Win32NT)
+            if (OsConstants.IsWindows)
             {
                 Debug.Assert(validLocations.Length == 2);
                 if (isSystemOp)

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

@@ -981,7 +981,7 @@ private void EnableSsl(uint info, SqlConnectionEncryptOption encrypt, bool integ
             // Channel Bindings as part of the Windows Authentication context build (SSL handshake must complete
             // before calling SNISecGenClientContext).
 #if NET
-            if (OperatingSystem.IsWindows())
+            if (OsConstants.IsWindows)
 #endif
             {
                 error = _physicalStateObj.WaitForSSLHandShakeToComplete(out protocol);

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParserStaticMethods.cs

@@ -4,7 +4,6 @@
 
 using System;
 using System.Globalization;
-using System.Runtime.InteropServices;
 using Microsoft.Data.Common;
 
 namespace Microsoft.Data.SqlClient
@@ -173,7 +172,7 @@ static internal byte[] GetNetworkPhysicalAddressForTdsLoginOnly()
 
             byte[] nicAddress = null;
 
-            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            if (OsConstants.IsWindows)
             {
                 // NIC address is stored in NetworkAddress key.  However, if NetworkAddressLocal key
                 // has a value that is not zero, then we cannot use the NetworkAddress key and must

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/UserAgent.cs

@@ -120,25 +120,24 @@ static UserAgent()
         // specific values.
         //
         string osType = Unknown;
-        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+        if (OsConstants.IsWindows)
         {
             osType = Windows;
         }
-        else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
+        else if (OsConstants.IsLinux)
         {
             osType = Linux;
         }
-        else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
+        else if (OsConstants.IsMacOS)
         {
             osType = macOS;
         }
-        // The FreeBSD platform doesn't exist in .NET Framework at all.
-        #if NET
-        else if (RuntimeInformation.IsOSPlatform(OSPlatform.FreeBSD))
+#if NET
+        else if (OsConstants.IsFreeBSD)
         {
             osType = FreeBSD;
         }
-        #endif
+#endif
 
         // Build it!
         Value = Build(

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlTypes/SqlFileStream.cs

@@ -102,7 +102,7 @@ public SqlFileStream(
             FileOptions options,
             long allocationSize)
         {
-            if (!ADP.IsWindows)
+            if (OsConstants.IsUnix)
             {
                 throw new PlatformNotSupportedException(Strings.SqlFileStream_NotSupported);
             }