DbConnectionHelper.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ 4.0 / 4.0 / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Data / System / Data / ProviderBase / DbConnectionHelper.cs / 1305376 / DbConnectionHelper.cs

                            //------------------------------------------------------------------------------ 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
//-----------------------------------------------------------------------------
 
namespace NAMESPACE { 

    using System; 
    using System.ComponentModel;
    using System.Data;
    using System.Data.Common;
    using System.Data.ProviderBase; 
    using System.Diagnostics;
    using System.Globalization; 
    using System.Runtime.ConstrainedExecution; 
    using System.Runtime.InteropServices;
    using System.Threading; 
    using SysTx = System.Transactions;
    using System.Diagnostics.CodeAnalysis;

    public sealed partial class CONNECTIONOBJECTNAME : DbConnection { 
        private static readonly DbConnectionFactory     _connectionFactory = CONNECTIONFACTORYOBJECTNAME;
        internal static readonly System.Security.CodeAccessPermission ExecutePermission = CONNECTIONOBJECTNAME.CreateExecutePermission(); 
 
        private DbConnectionOptions     _userConnectionOptions;
        private DbConnectionPoolGroup   _poolGroup; 
        private DbConnectionInternal    _innerConnection;
        private int                     _closeCount;          // used to distinguish between different uses of this object, so we don't have to maintain a list of it's children

        private static int _objectTypeCount; // Bid counter 
        internal readonly int ObjectID = System.Threading.Interlocked.Increment(ref _objectTypeCount);
 
        public CONNECTIONOBJECTNAME() : base() { 
            GC.SuppressFinalize(this);
            _innerConnection = DbConnectionClosedNeverOpened.SingletonInstance; 
        }

        // Copy Constructor
        private void CopyFrom(CONNECTIONOBJECTNAME connection) { // V1.2.3300 
            ADP.CheckArgumentNull(connection, "connection");
            _userConnectionOptions = connection.UserConnectionOptions; 
            _poolGroup = connection.PoolGroup; 

            // SQLBU 432115 
            //  Match the original connection's behavior for whether the connection was never opened,
            //  but ensure Clone is in the closed state.
            if (DbConnectionClosedNeverOpened.SingletonInstance == connection._innerConnection)
            { 
                _innerConnection = DbConnectionClosedNeverOpened.SingletonInstance;
            } 
            else 
            {
                _innerConnection = DbConnectionClosedPreviouslyOpened.SingletonInstance; 
            }
        }

        /// We use the _closeCount to avoid having to know about all our 
        ///  children; instead of keeping a collection of all the objects that
        ///  would be affected by a close, we simply increment the _closeCount 
        ///  and have each of our children check to see if they're "orphaned" 
        ///  
        internal int CloseCount { 
            get {
                return _closeCount;
            }
        } 

        internal DbConnectionFactory ConnectionFactory { 
            get { 
                return _connectionFactory;
            } 
        }

        internal DbConnectionOptions ConnectionOptions {
            get { 
                System.Data.ProviderBase.DbConnectionPoolGroup poolGroup = PoolGroup;
                return ((null != poolGroup) ? poolGroup.ConnectionOptions : null); 
            } 
        }
 
        private string ConnectionString_Get() {
            Bid.Trace( " %d#\n", ObjectID);
            bool hidePassword = InnerConnection.ShouldHidePassword;
            DbConnectionOptions connectionOptions = UserConnectionOptions; 
            return ((null != connectionOptions) ? connectionOptions.UsersConnectionString(hidePassword) : "");
        } 
        private void ConnectionString_Set(string value) { 
                DbConnectionOptions connectionOptions = null;
                System.Data.ProviderBase.DbConnectionPoolGroup poolGroup = ConnectionFactory.GetConnectionPoolGroup(value, null, ref connectionOptions); 
                DbConnectionInternal connectionInternal = InnerConnection;
                bool flag = connectionInternal.AllowSetConnectionString;
                if (flag) {
                    //try { 
                        // NOTE: There's a race condition with multiple threads changing
                        //       ConnectionString and any thread throws an exception 
                        // Closed->Busy: prevent Open during set_ConnectionString 
                        flag = SetInnerConnectionFrom(DbConnectionClosedBusy.SingletonInstance, connectionInternal);
                        if (flag) { 
                            _userConnectionOptions = connectionOptions;
                            _poolGroup = poolGroup;
                            _innerConnection = DbConnectionClosedNeverOpened.SingletonInstance;
                        } 
                    //}
                    //catch { 
                    //    // recover from exceptions to avoid sticking in busy state 
                    //    SetInnerConnectionFrom(connectionInternal, DbConnectionClosedBusy.SingletonInstance);
                    //    throw; 
                    //}
                }
                if (!flag) {
                    throw ADP.OpenConnectionPropertySet(ADP.ConnectionString, connectionInternal.State); 
                }
                if (Bid.TraceOn) { 
                    string cstr = ((null != connectionOptions) ? connectionOptions.UsersConnectionStringForTrace() : ""); 
                    Bid.Trace(" %d#, '%ls'\n", ObjectID, cstr);
                } 
        }

        internal DbConnectionInternal InnerConnection {
            get { 
                return _innerConnection;
            } 
        } 

        internal System.Data.ProviderBase.DbConnectionPoolGroup PoolGroup { 
            get {
                return _poolGroup;
            }
            set { 
                // when a poolgroup expires and the connection eventually activates, the pool entry will be replaced
                Debug.Assert(null != value, "null poolGroup"); 
                _poolGroup = value; 
            }
        } 

        [
        Browsable(false),
        DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), 
        RESNAMESPACE.ResDescriptionAttribute(Res.DbConnection_State),
        ] 
        override public ConnectionState State { 
            get {
                return InnerConnection.State; 
            }
        }

        internal DbConnectionOptions UserConnectionOptions { 
            get {
                return _userConnectionOptions; 
            } 
        }
 
        // Open->ClosedPreviouslyOpened, and doom the internal connection too...
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        internal void Abort(Exception e) {
            DbConnectionInternal innerConnection = _innerConnection;  // Should not cause memory allocation... 
            if (ConnectionState.Open == innerConnection.State) {
                Interlocked.CompareExchange(ref _innerConnection, DbConnectionClosedPreviouslyOpened.SingletonInstance, innerConnection); 
                innerConnection.DoomThisConnection(); 
            }
 
            // NOTE: we put the tracing last, because the ToString() calls (and
            // the Bid.Trace, for that matter) have no reliability contract and
            // will end the reliable try...
            if (e is OutOfMemoryException) { 
                Bid.Trace(" %d#, Aborting operation due to asynchronous exception: %ls\n", ObjectID, "OutOfMemory");
            } 
            else { 
                Bid.Trace(" %d#, Aborting operation due to asynchronous exception: %ls\n", ObjectID, e.ToString());
            } 
        }

        internal void AddWeakReference(object value, int tag) {
            InnerConnection.AddWeakReference(value, tag); 
        }
 
        // suppress this message - we cannot use SafeHandle here. Also, see notes in the code (VSTFDEVDIV# 560355) 
        [SuppressMessage("Microsoft.Reliability", "CA2004:RemoveCallsToGCKeepAlive")]
        override protected DbTransaction BeginDbTransaction(IsolationLevel isolationLevel) { 
            IntPtr hscp;

            Bid.ScopeEnter(out hscp, " %d#, isolationLevel=%d{ds.IsolationLevel}", ObjectID, (int)isolationLevel);
            try { 
                DbTransaction transaction = InnerConnection.BeginTransaction(isolationLevel);
 
                // VSTFDEVDIV# 560355 - InnerConnection doesn't maintain a ref on the outer connection (this) and 
                //   subsequently leaves open the possibility that the outer connection could be GC'ed before the SqlTransaction
                //   is fully hooked up (leaving a SqlTransaction with a null connection property). Ensure that this is reachable 
                //   until the completion of BeginTransaction with KeepAlive
                GC.KeepAlive ( this );

                return transaction; 
            } finally {
                Bid.ScopeLeave(ref hscp); 
            } 
        }
 
        override protected DbCommand CreateDbCommand() {
            DbCommand command = null;
            IntPtr hscp;
            Bid.ScopeEnter(out hscp, " %d#\n", ObjectID); 
            try {
                DbProviderFactory providerFactory = ConnectionFactory.ProviderFactory; 
                command = providerFactory.CreateCommand(); 
                command.Connection = this;
            } 
            finally {
                Bid.ScopeLeave(ref hscp);
            }
            return command; 
        }
 
        private static System.Security.CodeAccessPermission CreateExecutePermission() { 
#if ORACLE
            OraclePermission p = new OraclePermission(System.Security.Permissions.PermissionState.None); 
            p.Add(String.Empty, String.Empty, KeyRestrictionBehavior.AllowOnly);
            return p;
#else
            DBDataPermission p = (DBDataPermission)CONNECTIONFACTORYOBJECTNAME.ProviderFactory.CreatePermission(System.Security.Permissions.PermissionState.None); 
            p.Add(String.Empty, String.Empty, KeyRestrictionBehavior.AllowOnly);
            return p; 
#endif 
        }
 
        override protected void Dispose(bool disposing) {
            if (disposing) {
                _userConnectionOptions = null;
                _poolGroup= null; 
                Close();
            } 
            DisposeMe(disposing); 
            base.Dispose(disposing); // notify base classes
        } 

        // NOTE: This is just a private helper because OracleClient V1.1 shipped
        // with a different argument name and it's a breaking change to not use
        // the same argument names in V2.0 (VB Named Parameter Binding--Ick) 
        private void EnlistDistributedTransactionHelper(System.EnterpriseServices.ITransaction transaction) {
            System.Security.PermissionSet permissionSet = new System.Security.PermissionSet(System.Security.Permissions.PermissionState.None); 
            permissionSet.AddPermission(CONNECTIONOBJECTNAME.ExecutePermission); // MDAC 81476 
            permissionSet.AddPermission(new System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityPermissionFlag.UnmanagedCode));
            permissionSet.Demand(); 

            Bid.Trace( " %d#, Connection enlisting in a transaction.\n", ObjectID);
            SysTx.Transaction indigoTransaction = null;
 
            if (null != transaction) {
                indigoTransaction = SysTx.TransactionInterop.GetTransactionFromDtcTransaction((SysTx.IDtcTransaction)transaction); 
            } 

            // NOTE: since transaction enlistment involves round trips to the 
            // server, we don't want to lock here, we'll handle the race conditions
            // elsewhere.
            InnerConnection.EnlistTransaction(indigoTransaction);
 
            // NOTE: If this outer connection were to be GC'd while we're
            // enlisting, the pooler would attempt to reclaim the inner connection 
            // while we're attempting to enlist; not sure how likely that is but 
            // we should consider a GC.KeepAlive(this) here.
            GC.KeepAlive(this); 
        }

        override public void EnlistTransaction(SysTx.Transaction transaction) {
            CONNECTIONOBJECTNAME.ExecutePermission.Demand(); 

            Bid.Trace( " %d#, Connection enlisting in a transaction.\n", ObjectID); 
 
            // If we're currently enlisted in a transaction and we were called
            // on the EnlistTransaction method (Whidbey) we're not allowed to 
            // enlist in a different transaction.

            DbConnectionInternal innerConnection = InnerConnection;
 
            // NOTE: since transaction enlistment involves round trips to the
            // server, we don't want to lock here, we'll handle the race conditions 
            // elsewhere. 
            SysTx.Transaction enlistedTransaction = innerConnection.EnlistedTransaction;
            if (enlistedTransaction != null) { 
                // Allow calling enlist if already enlisted (no-op)
                if (enlistedTransaction.Equals(transaction)) {
                    return;
                } 

                // Allow enlisting in a different transaction if the enlisted transaction has completed. 
                if (enlistedTransaction.TransactionInformation.Status == SysTx.TransactionStatus.Active) 
                {
                    throw ADP.TransactionPresent(); 
                }
            }
            innerConnection.EnlistTransaction(transaction);
 
            // NOTE: If this outer connection were to be GC'd while we're
            // enlisting, the pooler would attempt to reclaim the inner connection 
            // while we're attempting to enlist; not sure how likely that is but 
            // we should consider a GC.KeepAlive(this) here.
            GC.KeepAlive(this); 
        }

        private DbMetaDataFactory GetMetaDataFactory(DbConnectionInternal internalConnection) {
            return ConnectionFactory.GetMetaDataFactory(_poolGroup, internalConnection); 
        }
 
        internal DbMetaDataFactory GetMetaDataFactoryInternal(DbConnectionInternal internalConnection) { 
            return GetMetaDataFactory(internalConnection);
        } 

        override public  DataTable GetSchema() {
            return this.GetSchema(DbMetaDataCollectionNames.MetaDataCollections, null);
        } 

        override public DataTable GetSchema(string collectionName) { 
            return this.GetSchema(collectionName, null); 
        }
 
        override public DataTable GetSchema(string collectionName, string[] restrictionValues) {
            // NOTE: This is virtual because not all providers may choose to support
            //       returning schema data
            CONNECTIONOBJECTNAME.ExecutePermission.Demand(); 
            return InnerConnection.GetSchema(ConnectionFactory, PoolGroup, this, collectionName, restrictionValues);
        } 
 
        internal void NotifyWeakReference(int message) {
            InnerConnection.NotifyWeakReference(message); 
        }

        internal void PermissionDemand() {
            Debug.Assert(DbConnectionClosedConnecting.SingletonInstance == _innerConnection, "not connecting"); 

            System.Data.ProviderBase.DbConnectionPoolGroup poolGroup = PoolGroup; 
            DbConnectionOptions connectionOptions = ((null != poolGroup) ? poolGroup.ConnectionOptions : null); 
            if ((null == connectionOptions) || connectionOptions.IsEmpty) {
                throw ADP.NoConnectionString(); 
            }

            DbConnectionOptions userConnectionOptions = UserConnectionOptions;
            Debug.Assert(null != userConnectionOptions, "null UserConnectionOptions"); 

            userConnectionOptions.DemandPermission(); 
        } 

        internal void RemoveWeakReference(object value) { 
            InnerConnection.RemoveWeakReference(value);
        }

        // OpenBusy->Closed (previously opened) 
        // Connecting->Open
        internal void SetInnerConnectionEvent(DbConnectionInternal to) { 
            // Set's the internal connection without verifying that it's a specific value 
            Debug.Assert(null != _innerConnection, "null InnerConnection");
            Debug.Assert(null != to, "to null InnerConnection"); 

            ConnectionState originalState = _innerConnection.State & ConnectionState.Open;
            ConnectionState currentState = to.State & ConnectionState.Open;
 
            if ((originalState != currentState) && (ConnectionState.Closed == currentState)) {
                // Increment the close count whenever we switch to Closed 
                unchecked { _closeCount++; } 
            }
 
            _innerConnection = to;

            if (ConnectionState.Closed == originalState && ConnectionState.Open == currentState) {
                OnStateChange(DbConnectionInternal.StateChangeOpen); 
            }
            else if (ConnectionState.Open == originalState && ConnectionState.Closed == currentState) { 
                OnStateChange(DbConnectionInternal.StateChangeClosed); 
            }
            else { 
                Debug.Assert(false, "unexpected state switch");
                if (originalState != currentState) {
                    OnStateChange(new StateChangeEventArgs(originalState, currentState));
                } 
            }
        } 
 
        // this method is used to securely change state with the resource being
        // the open connection protected by the connectionstring via a permission demand 

        // Closed->Connecting: prevent set_ConnectionString during Open
        // Open->OpenBusy: guarantee internal connection is returned to correct pool
        // Closed->ClosedBusy: prevent Open during set_ConnectionString 
        internal bool SetInnerConnectionFrom(DbConnectionInternal to, DbConnectionInternal from) {
            // Set's the internal connection, verifying that it's a specific value before doing so. 
            Debug.Assert(null != _innerConnection, "null InnerConnection"); 
            Debug.Assert(null != from, "from null InnerConnection");
            Debug.Assert(null != to, "to null InnerConnection"); 

            bool result = (from == Interlocked.CompareExchange(ref _innerConnection, to, from));
            return result;
        } 

        // ClosedBusy->Closed (never opened) 
        // Connecting->Closed (exception during open, return to previous closed state) 
        internal void SetInnerConnectionTo(DbConnectionInternal to) {
            // Set's the internal connection without verifying that it's a specific value 
            Debug.Assert(null != _innerConnection, "null InnerConnection");
            Debug.Assert(null != to, "to null InnerConnection");
            _innerConnection = to;
        } 

        [ConditionalAttribute("DEBUG")] 
        internal static void VerifyExecutePermission() { 
            try {
                // use this to help validate this code path is only used after the following permission has been previously demanded in the current codepath 
                CONNECTIONOBJECTNAME.ExecutePermission.Demand();
            }
            catch(System.Security.SecurityException) {
                System.Diagnostics.Debug.Assert(false, "unexpected SecurityException for current codepath"); 
                throw;
            } 
        } 
    }
} 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
//------------------------------------------------------------------------------ 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// [....] 
//-----------------------------------------------------------------------------
 
namespace NAMESPACE { 

    using System; 
    using System.ComponentModel;
    using System.Data;
    using System.Data.Common;
    using System.Data.ProviderBase; 
    using System.Diagnostics;
    using System.Globalization; 
    using System.Runtime.ConstrainedExecution; 
    using System.Runtime.InteropServices;
    using System.Threading; 
    using SysTx = System.Transactions;
    using System.Diagnostics.CodeAnalysis;

    public sealed partial class CONNECTIONOBJECTNAME : DbConnection { 
        private static readonly DbConnectionFactory     _connectionFactory = CONNECTIONFACTORYOBJECTNAME;
        internal static readonly System.Security.CodeAccessPermission ExecutePermission = CONNECTIONOBJECTNAME.CreateExecutePermission(); 
 
        private DbConnectionOptions     _userConnectionOptions;
        private DbConnectionPoolGroup   _poolGroup; 
        private DbConnectionInternal    _innerConnection;
        private int                     _closeCount;          // used to distinguish between different uses of this object, so we don't have to maintain a list of it's children

        private static int _objectTypeCount; // Bid counter 
        internal readonly int ObjectID = System.Threading.Interlocked.Increment(ref _objectTypeCount);
 
        public CONNECTIONOBJECTNAME() : base() { 
            GC.SuppressFinalize(this);
            _innerConnection = DbConnectionClosedNeverOpened.SingletonInstance; 
        }

        // Copy Constructor
        private void CopyFrom(CONNECTIONOBJECTNAME connection) { // V1.2.3300 
            ADP.CheckArgumentNull(connection, "connection");
            _userConnectionOptions = connection.UserConnectionOptions; 
            _poolGroup = connection.PoolGroup; 

            // SQLBU 432115 
            //  Match the original connection's behavior for whether the connection was never opened,
            //  but ensure Clone is in the closed state.
            if (DbConnectionClosedNeverOpened.SingletonInstance == connection._innerConnection)
            { 
                _innerConnection = DbConnectionClosedNeverOpened.SingletonInstance;
            } 
            else 
            {
                _innerConnection = DbConnectionClosedPreviouslyOpened.SingletonInstance; 
            }
        }

        /// We use the _closeCount to avoid having to know about all our 
        ///  children; instead of keeping a collection of all the objects that
        ///  would be affected by a close, we simply increment the _closeCount 
        ///  and have each of our children check to see if they're "orphaned" 
        ///  
        internal int CloseCount { 
            get {
                return _closeCount;
            }
        } 

        internal DbConnectionFactory ConnectionFactory { 
            get { 
                return _connectionFactory;
            } 
        }

        internal DbConnectionOptions ConnectionOptions {
            get { 
                System.Data.ProviderBase.DbConnectionPoolGroup poolGroup = PoolGroup;
                return ((null != poolGroup) ? poolGroup.ConnectionOptions : null); 
            } 
        }
 
        private string ConnectionString_Get() {
            Bid.Trace( " %d#\n", ObjectID);
            bool hidePassword = InnerConnection.ShouldHidePassword;
            DbConnectionOptions connectionOptions = UserConnectionOptions; 
            return ((null != connectionOptions) ? connectionOptions.UsersConnectionString(hidePassword) : "");
        } 
        private void ConnectionString_Set(string value) { 
                DbConnectionOptions connectionOptions = null;
                System.Data.ProviderBase.DbConnectionPoolGroup poolGroup = ConnectionFactory.GetConnectionPoolGroup(value, null, ref connectionOptions); 
                DbConnectionInternal connectionInternal = InnerConnection;
                bool flag = connectionInternal.AllowSetConnectionString;
                if (flag) {
                    //try { 
                        // NOTE: There's a race condition with multiple threads changing
                        //       ConnectionString and any thread throws an exception 
                        // Closed->Busy: prevent Open during set_ConnectionString 
                        flag = SetInnerConnectionFrom(DbConnectionClosedBusy.SingletonInstance, connectionInternal);
                        if (flag) { 
                            _userConnectionOptions = connectionOptions;
                            _poolGroup = poolGroup;
                            _innerConnection = DbConnectionClosedNeverOpened.SingletonInstance;
                        } 
                    //}
                    //catch { 
                    //    // recover from exceptions to avoid sticking in busy state 
                    //    SetInnerConnectionFrom(connectionInternal, DbConnectionClosedBusy.SingletonInstance);
                    //    throw; 
                    //}
                }
                if (!flag) {
                    throw ADP.OpenConnectionPropertySet(ADP.ConnectionString, connectionInternal.State); 
                }
                if (Bid.TraceOn) { 
                    string cstr = ((null != connectionOptions) ? connectionOptions.UsersConnectionStringForTrace() : ""); 
                    Bid.Trace(" %d#, '%ls'\n", ObjectID, cstr);
                } 
        }

        internal DbConnectionInternal InnerConnection {
            get { 
                return _innerConnection;
            } 
        } 

        internal System.Data.ProviderBase.DbConnectionPoolGroup PoolGroup { 
            get {
                return _poolGroup;
            }
            set { 
                // when a poolgroup expires and the connection eventually activates, the pool entry will be replaced
                Debug.Assert(null != value, "null poolGroup"); 
                _poolGroup = value; 
            }
        } 

        [
        Browsable(false),
        DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), 
        RESNAMESPACE.ResDescriptionAttribute(Res.DbConnection_State),
        ] 
        override public ConnectionState State { 
            get {
                return InnerConnection.State; 
            }
        }

        internal DbConnectionOptions UserConnectionOptions { 
            get {
                return _userConnectionOptions; 
            } 
        }
 
        // Open->ClosedPreviouslyOpened, and doom the internal connection too...
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        internal void Abort(Exception e) {
            DbConnectionInternal innerConnection = _innerConnection;  // Should not cause memory allocation... 
            if (ConnectionState.Open == innerConnection.State) {
                Interlocked.CompareExchange(ref _innerConnection, DbConnectionClosedPreviouslyOpened.SingletonInstance, innerConnection); 
                innerConnection.DoomThisConnection(); 
            }
 
            // NOTE: we put the tracing last, because the ToString() calls (and
            // the Bid.Trace, for that matter) have no reliability contract and
            // will end the reliable try...
            if (e is OutOfMemoryException) { 
                Bid.Trace(" %d#, Aborting operation due to asynchronous exception: %ls\n", ObjectID, "OutOfMemory");
            } 
            else { 
                Bid.Trace(" %d#, Aborting operation due to asynchronous exception: %ls\n", ObjectID, e.ToString());
            } 
        }

        internal void AddWeakReference(object value, int tag) {
            InnerConnection.AddWeakReference(value, tag); 
        }
 
        // suppress this message - we cannot use SafeHandle here. Also, see notes in the code (VSTFDEVDIV# 560355) 
        [SuppressMessage("Microsoft.Reliability", "CA2004:RemoveCallsToGCKeepAlive")]
        override protected DbTransaction BeginDbTransaction(IsolationLevel isolationLevel) { 
            IntPtr hscp;

            Bid.ScopeEnter(out hscp, " %d#, isolationLevel=%d{ds.IsolationLevel}", ObjectID, (int)isolationLevel);
            try { 
                DbTransaction transaction = InnerConnection.BeginTransaction(isolationLevel);
 
                // VSTFDEVDIV# 560355 - InnerConnection doesn't maintain a ref on the outer connection (this) and 
                //   subsequently leaves open the possibility that the outer connection could be GC'ed before the SqlTransaction
                //   is fully hooked up (leaving a SqlTransaction with a null connection property). Ensure that this is reachable 
                //   until the completion of BeginTransaction with KeepAlive
                GC.KeepAlive ( this );

                return transaction; 
            } finally {
                Bid.ScopeLeave(ref hscp); 
            } 
        }
 
        override protected DbCommand CreateDbCommand() {
            DbCommand command = null;
            IntPtr hscp;
            Bid.ScopeEnter(out hscp, " %d#\n", ObjectID); 
            try {
                DbProviderFactory providerFactory = ConnectionFactory.ProviderFactory; 
                command = providerFactory.CreateCommand(); 
                command.Connection = this;
            } 
            finally {
                Bid.ScopeLeave(ref hscp);
            }
            return command; 
        }
 
        private static System.Security.CodeAccessPermission CreateExecutePermission() { 
#if ORACLE
            OraclePermission p = new OraclePermission(System.Security.Permissions.PermissionState.None); 
            p.Add(String.Empty, String.Empty, KeyRestrictionBehavior.AllowOnly);
            return p;
#else
            DBDataPermission p = (DBDataPermission)CONNECTIONFACTORYOBJECTNAME.ProviderFactory.CreatePermission(System.Security.Permissions.PermissionState.None); 
            p.Add(String.Empty, String.Empty, KeyRestrictionBehavior.AllowOnly);
            return p; 
#endif 
        }
 
        override protected void Dispose(bool disposing) {
            if (disposing) {
                _userConnectionOptions = null;
                _poolGroup= null; 
                Close();
            } 
            DisposeMe(disposing); 
            base.Dispose(disposing); // notify base classes
        } 

        // NOTE: This is just a private helper because OracleClient V1.1 shipped
        // with a different argument name and it's a breaking change to not use
        // the same argument names in V2.0 (VB Named Parameter Binding--Ick) 
        private void EnlistDistributedTransactionHelper(System.EnterpriseServices.ITransaction transaction) {
            System.Security.PermissionSet permissionSet = new System.Security.PermissionSet(System.Security.Permissions.PermissionState.None); 
            permissionSet.AddPermission(CONNECTIONOBJECTNAME.ExecutePermission); // MDAC 81476 
            permissionSet.AddPermission(new System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityPermissionFlag.UnmanagedCode));
            permissionSet.Demand(); 

            Bid.Trace( " %d#, Connection enlisting in a transaction.\n", ObjectID);
            SysTx.Transaction indigoTransaction = null;
 
            if (null != transaction) {
                indigoTransaction = SysTx.TransactionInterop.GetTransactionFromDtcTransaction((SysTx.IDtcTransaction)transaction); 
            } 

            // NOTE: since transaction enlistment involves round trips to the 
            // server, we don't want to lock here, we'll handle the race conditions
            // elsewhere.
            InnerConnection.EnlistTransaction(indigoTransaction);
 
            // NOTE: If this outer connection were to be GC'd while we're
            // enlisting, the pooler would attempt to reclaim the inner connection 
            // while we're attempting to enlist; not sure how likely that is but 
            // we should consider a GC.KeepAlive(this) here.
            GC.KeepAlive(this); 
        }

        override public void EnlistTransaction(SysTx.Transaction transaction) {
            CONNECTIONOBJECTNAME.ExecutePermission.Demand(); 

            Bid.Trace( " %d#, Connection enlisting in a transaction.\n", ObjectID); 
 
            // If we're currently enlisted in a transaction and we were called
            // on the EnlistTransaction method (Whidbey) we're not allowed to 
            // enlist in a different transaction.

            DbConnectionInternal innerConnection = InnerConnection;
 
            // NOTE: since transaction enlistment involves round trips to the
            // server, we don't want to lock here, we'll handle the race conditions 
            // elsewhere. 
            SysTx.Transaction enlistedTransaction = innerConnection.EnlistedTransaction;
            if (enlistedTransaction != null) { 
                // Allow calling enlist if already enlisted (no-op)
                if (enlistedTransaction.Equals(transaction)) {
                    return;
                } 

                // Allow enlisting in a different transaction if the enlisted transaction has completed. 
                if (enlistedTransaction.TransactionInformation.Status == SysTx.TransactionStatus.Active) 
                {
                    throw ADP.TransactionPresent(); 
                }
            }
            innerConnection.EnlistTransaction(transaction);
 
            // NOTE: If this outer connection were to be GC'd while we're
            // enlisting, the pooler would attempt to reclaim the inner connection 
            // while we're attempting to enlist; not sure how likely that is but 
            // we should consider a GC.KeepAlive(this) here.
            GC.KeepAlive(this); 
        }

        private DbMetaDataFactory GetMetaDataFactory(DbConnectionInternal internalConnection) {
            return ConnectionFactory.GetMetaDataFactory(_poolGroup, internalConnection); 
        }
 
        internal DbMetaDataFactory GetMetaDataFactoryInternal(DbConnectionInternal internalConnection) { 
            return GetMetaDataFactory(internalConnection);
        } 

        override public  DataTable GetSchema() {
            return this.GetSchema(DbMetaDataCollectionNames.MetaDataCollections, null);
        } 

        override public DataTable GetSchema(string collectionName) { 
            return this.GetSchema(collectionName, null); 
        }
 
        override public DataTable GetSchema(string collectionName, string[] restrictionValues) {
            // NOTE: This is virtual because not all providers may choose to support
            //       returning schema data
            CONNECTIONOBJECTNAME.ExecutePermission.Demand(); 
            return InnerConnection.GetSchema(ConnectionFactory, PoolGroup, this, collectionName, restrictionValues);
        } 
 
        internal void NotifyWeakReference(int message) {
            InnerConnection.NotifyWeakReference(message); 
        }

        internal void PermissionDemand() {
            Debug.Assert(DbConnectionClosedConnecting.SingletonInstance == _innerConnection, "not connecting"); 

            System.Data.ProviderBase.DbConnectionPoolGroup poolGroup = PoolGroup; 
            DbConnectionOptions connectionOptions = ((null != poolGroup) ? poolGroup.ConnectionOptions : null); 
            if ((null == connectionOptions) || connectionOptions.IsEmpty) {
                throw ADP.NoConnectionString(); 
            }

            DbConnectionOptions userConnectionOptions = UserConnectionOptions;
            Debug.Assert(null != userConnectionOptions, "null UserConnectionOptions"); 

            userConnectionOptions.DemandPermission(); 
        } 

        internal void RemoveWeakReference(object value) { 
            InnerConnection.RemoveWeakReference(value);
        }

        // OpenBusy->Closed (previously opened) 
        // Connecting->Open
        internal void SetInnerConnectionEvent(DbConnectionInternal to) { 
            // Set's the internal connection without verifying that it's a specific value 
            Debug.Assert(null != _innerConnection, "null InnerConnection");
            Debug.Assert(null != to, "to null InnerConnection"); 

            ConnectionState originalState = _innerConnection.State & ConnectionState.Open;
            ConnectionState currentState = to.State & ConnectionState.Open;
 
            if ((originalState != currentState) && (ConnectionState.Closed == currentState)) {
                // Increment the close count whenever we switch to Closed 
                unchecked { _closeCount++; } 
            }
 
            _innerConnection = to;

            if (ConnectionState.Closed == originalState && ConnectionState.Open == currentState) {
                OnStateChange(DbConnectionInternal.StateChangeOpen); 
            }
            else if (ConnectionState.Open == originalState && ConnectionState.Closed == currentState) { 
                OnStateChange(DbConnectionInternal.StateChangeClosed); 
            }
            else { 
                Debug.Assert(false, "unexpected state switch");
                if (originalState != currentState) {
                    OnStateChange(new StateChangeEventArgs(originalState, currentState));
                } 
            }
        } 
 
        // this method is used to securely change state with the resource being
        // the open connection protected by the connectionstring via a permission demand 

        // Closed->Connecting: prevent set_ConnectionString during Open
        // Open->OpenBusy: guarantee internal connection is returned to correct pool
        // Closed->ClosedBusy: prevent Open during set_ConnectionString 
        internal bool SetInnerConnectionFrom(DbConnectionInternal to, DbConnectionInternal from) {
            // Set's the internal connection, verifying that it's a specific value before doing so. 
            Debug.Assert(null != _innerConnection, "null InnerConnection"); 
            Debug.Assert(null != from, "from null InnerConnection");
            Debug.Assert(null != to, "to null InnerConnection"); 

            bool result = (from == Interlocked.CompareExchange(ref _innerConnection, to, from));
            return result;
        } 

        // ClosedBusy->Closed (never opened) 
        // Connecting->Closed (exception during open, return to previous closed state) 
        internal void SetInnerConnectionTo(DbConnectionInternal to) {
            // Set's the internal connection without verifying that it's a specific value 
            Debug.Assert(null != _innerConnection, "null InnerConnection");
            Debug.Assert(null != to, "to null InnerConnection");
            _innerConnection = to;
        } 

        [ConditionalAttribute("DEBUG")] 
        internal static void VerifyExecutePermission() { 
            try {
                // use this to help validate this code path is only used after the following permission has been previously demanded in the current codepath 
                CONNECTIONOBJECTNAME.ExecutePermission.Demand();
            }
            catch(System.Security.SecurityException) {
                System.Diagnostics.Debug.Assert(false, "unexpected SecurityException for current codepath"); 
                throw;
            } 
        } 
    }
} 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
                        

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