C# DbConnectionInternal.PrepareForReplaceConnection方法代码示例

        /// <summary>
        /// Creates a new connection to replace an existing connection
        /// </summary>
        /// <param name="owningObject">Outer connection that currently owns <paramref name="oldConnection"/></param>
        /// <param name="userOptions">Options used to create the new connection</param>
        /// <param name="oldConnection">Inner connection that will be replaced</param>
        /// <returns>A new inner connection that is attached to the <paramref name="owningObject"/></returns>
        internal DbConnectionInternal ReplaceConnection(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
        {
            DbConnectionInternal newConnection = UserCreateRequest(owningObject, userOptions, oldConnection);

            if (newConnection != null)
            {
                PrepareConnection(owningObject, newConnection);
                oldConnection.PrepareForReplaceConnection();
                oldConnection.DeactivateConnection();
                oldConnection.Dispose();
            }

            return newConnection;
        }

        internal bool TryGetConnection(DbConnection owningConnection, TaskCompletionSource<DbConnectionInternal> retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, out DbConnectionInternal connection)
        {
            Debug.Assert(null != owningConnection, "null owningConnection?");

            DbConnectionPoolGroup poolGroup;
            DbConnectionPool connectionPool;
            connection = null;

            //  Work around race condition with clearing the pool between GetConnectionPool obtaining pool 
            //  and GetConnection on the pool checking the pool state.  Clearing the pool in this window
            //  will switch the pool into the ShuttingDown state, and GetConnection will return null.
            //  There is probably a better solution involving locking the pool/group, but that entails a major
            //  re-design of the connection pooling synchronization, so is post-poned for now.

            // Use retriesLeft to prevent CPU spikes with incremental sleep
            // start with one msec, double the time every retry
            // max time is: 1 + 2 + 4 + ... + 2^(retries-1) == 2^retries -1 == 1023ms (for 10 retries)
            int retriesLeft = 10;
            int timeBetweenRetriesMilliseconds = 1;

            do
            {
                poolGroup = GetConnectionPoolGroup(owningConnection);
                // Doing this on the callers thread is important because it looks up the WindowsIdentity from the thread.
                connectionPool = GetConnectionPool(owningConnection, poolGroup);
                if (null == connectionPool)
                {
                    // If GetConnectionPool returns null, we can be certain that
                    // this connection should not be pooled via DbConnectionPool
                    // or have a disabled pool entry.
                    poolGroup = GetConnectionPoolGroup(owningConnection); // previous entry have been disabled

                    if (retry != null)
                    {
                        Task<DbConnectionInternal> newTask;
                        CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
                        lock (s_pendingOpenNonPooled)
                        {
                            // look for an available task slot (completed or empty)
                            int idx;
                            for (idx = 0; idx < s_pendingOpenNonPooled.Length; idx++)
                            {
                                Task task = s_pendingOpenNonPooled[idx];
                                if (task == null)
                                {
                                    s_pendingOpenNonPooled[idx] = GetCompletedTask();
                                    break;
                                }
                                else if (task.IsCompleted)
                                {
                                    break;
                                }
                            }

                            // if didn't find one, pick the next one in round-robbin fashion
                            if (idx == s_pendingOpenNonPooled.Length)
                            {
                                idx = s_pendingOpenNonPooledNext++ % s_pendingOpenNonPooled.Length;
                            }

                            // now that we have an antecedent task, schedule our work when it is completed.
                            // If it is a new slot or a compelted task, this continuation will start right away.
                            newTask = s_pendingOpenNonPooled[idx].ContinueWith((_) =>
                            {
                                var newConnection = CreateNonPooledConnection(owningConnection, poolGroup, userOptions);
                                if ((oldConnection != null) && (oldConnection.State == ConnectionState.Open))
                                {
                                    oldConnection.PrepareForReplaceConnection();
                                    oldConnection.Dispose();
                                }
                                return newConnection;
                            }, cancellationTokenSource.Token, TaskContinuationOptions.LongRunning, TaskScheduler.Default);

                            // Place this new task in the slot so any future work will be queued behind it
                            s_pendingOpenNonPooled[idx] = newTask;
                        }

                        // Set up the timeout (if needed)
                        if (owningConnection.ConnectionTimeout > 0)
                        {
                            int connectionTimeoutMilliseconds = owningConnection.ConnectionTimeout * 1000;
                            cancellationTokenSource.CancelAfter(connectionTimeoutMilliseconds);
                        }

                        // once the task is done, propagate the final results to the original caller
                        newTask.ContinueWith((task) =>
                        {
                            cancellationTokenSource.Dispose();
                            if (task.IsCanceled)
                            {
                                retry.TrySetException(ADP.ExceptionWithStackTrace(ADP.NonPooledOpenTimeout()));
                            }
                            else if (task.IsFaulted)
                            {
                                retry.TrySetException(task.Exception.InnerException);
                            }
                            else
                            {
                                if (!retry.TrySetResult(task.Result))
                                {
//.........这里部分代码省略.........