528 lines
18 KiB
C#
528 lines
18 KiB
C#
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// ---------------------------------------------------------------------------
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// <copyright file="Session.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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// ---------------------------------------------------------------------------
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// ---------------------------------------------------------------------
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// <summary>
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// </summary>
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// ---------------------------------------------------------------------
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namespace Microsoft.Database.Isam
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{
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using System;
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using Microsoft.Isam.Esent.Interop;
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/// <summary>
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/// A Session is the transactional context for the ISAM. It can be used to
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/// begin, commit, or abort transactions that influence when changes made
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/// to databases are kept or discarded.
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/// <para>
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/// The session object currently also controls which databases can be
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/// accessed by the ISAM.
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/// </para>
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/// </summary>
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public class IsamSession : IDisposable
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{
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/// <summary>
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/// The instance
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/// </summary>
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private readonly IsamInstance isamInstance;
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/// <summary>
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/// The sesid
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/// </summary>
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private readonly JET_SESID sesid;
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/// <summary>
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/// The cleanup
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/// </summary>
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private bool cleanup = false;
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/// <summary>
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/// The disposed
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/// </summary>
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private bool disposed = false;
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/// <summary>
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/// The temporary database
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/// </summary>
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private TemporaryDatabase temporaryDatabase = null;
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/// <summary>
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/// The transaction level
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/// </summary>
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private long transactionLevel = 0;
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/// <summary>
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/// The transaction level identifier
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/// </summary>
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private long[] transactionLevelID = null;
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/// <summary>
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/// Initializes a new instance of the <see cref="IsamSession"/> class.
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/// </summary>
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/// <param name="isamInstance">The instance.</param>
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internal IsamSession(IsamInstance isamInstance)
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{
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lock (isamInstance)
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{
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this.isamInstance = isamInstance;
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Api.JetBeginSession(isamInstance.Inst, out this.sesid, null, null);
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this.cleanup = true;
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this.transactionLevelID = new long[7]; // JET only supports 7 levels
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}
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}
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/// <summary>
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/// Finalizes an instance of the IsamSession class.
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/// </summary>
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~IsamSession()
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{
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this.Dispose(false);
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}
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/// <summary>
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/// Gets the instance that created this session.
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/// </summary>
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public IsamInstance IsamInstance
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{
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get
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{
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return this.isamInstance;
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}
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}
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/// <summary>
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/// Gets the ID of the session's current transaction.
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/// </summary>
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/// <remarks>
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/// The transaction ID is incremented every time the session's current
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/// transaction save point (level) reaches zero such that the session
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/// is no longer considered to be in a transaction.
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/// </remarks>
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public long TransactionID
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{
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get
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{
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this.CheckDisposed();
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return this.transactionLevelID[0];
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}
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}
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/// <summary>
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/// Gets the save point (level) of the session's current transaction.
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/// </summary>
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/// <remarks>
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/// Every time a new transaction is begun, the save point (level) of
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/// the session's current transaction is increased. Every time a
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/// transaction is successfully committed or aborted, the save point
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/// (level) of the session's current transaction is decreased. If the
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/// save point (level) of the session's current transaction is zero
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/// then the session is not considered to be in a transaction.
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/// However, individual operations performed using the session will
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/// still be in a transaction.
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/// </remarks>
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public long TransactionLevel
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{
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get
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{
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this.CheckDisposed();
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return this.transactionLevel;
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}
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}
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/// <summary>
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/// Gets the sesid.
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/// </summary>
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/// <value>
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/// The sesid.
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/// </value>
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internal JET_SESID Sesid
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{
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get
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{
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return this.sesid;
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}
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}
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/// <summary>
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/// Gets or sets a value indicating whether [disposed].
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/// </summary>
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/// <value>
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/// <c>true</c> if [disposed]; otherwise, <c>false</c>.
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/// </value>
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internal bool Disposed
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{
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get
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{
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return this.disposed || this.isamInstance.Disposed;
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}
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set
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{
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this.disposed = value;
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}
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}
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/// <summary>
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/// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
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/// </summary>
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public void Dispose()
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{
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lock (this)
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{
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this.Dispose(true);
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}
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GC.SuppressFinalize(this);
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}
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/// <summary>
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/// Creates a new database at the specified location
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/// </summary>
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/// <param name="databaseName">The file name (relative or absolute) at which the database will be created</param>
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/// <remarks>
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/// The new database will automatically be attached to the instance.
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/// See Session.AttachDatabase for more information.
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/// </remarks>
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public void CreateDatabase(string databaseName)
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{
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lock (this)
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{
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this.CheckDisposed();
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JET_DBID dbid;
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Api.JetCreateDatabase(this.Sesid, databaseName, null, out dbid, CreateDatabaseGrbit.None);
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Api.JetCloseDatabase(this.Sesid, dbid, CloseDatabaseGrbit.None);
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}
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}
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/// <summary>
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/// Attaches an existing database at the specified location
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/// </summary>
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/// <param name="databaseName">The file name (relative or absolute) at which the database will be attached</param>
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/// <remarks>
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/// Attaching a database to the instance enables that database to be
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/// opened for access. When a database is attached, its file is
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/// opened and so must be available to be locked as required. The
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/// file will be held open until the database is detached or until the
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/// instance is disposed.
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/// </remarks>
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public void AttachDatabase(string databaseName)
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{
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lock (this)
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{
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this.CheckDisposed();
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AttachDatabaseGrbit grbit = AttachDatabaseGrbit.None;
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if (this.isamInstance.ReadOnly)
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{
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grbit |= AttachDatabaseGrbit.ReadOnly;
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}
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Api.JetAttachDatabase(this.Sesid, databaseName, grbit);
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}
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}
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/// <summary>
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/// Detaches an attached database at the specified location
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/// </summary>
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/// <param name="databaseName">The file name (relative or absolute) at which the database will be detached</param>
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/// <remarks>
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/// Detaching a database from the instance will close its file and
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/// will make it no longer possible to open that database.
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/// </remarks>
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public void DetachDatabase(string databaseName)
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{
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lock (this)
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{
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this.CheckDisposed();
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Api.JetDetachDatabase(this.Sesid, databaseName);
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}
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}
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/// <summary>
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/// Determines if there is a database at the specified location
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/// </summary>
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/// <param name="databaseName">The file name (relative or absolute) at which the database may exist</param>
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/// <returns>true if the database exists and is a valid database file, false otherwise</returns>
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public bool Exists(string databaseName)
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{
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lock (this)
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{
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this.CheckDisposed();
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try
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{
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AttachDatabaseGrbit grbit = AttachDatabaseGrbit.None;
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if (this.isamInstance.ReadOnly)
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{
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grbit |= AttachDatabaseGrbit.ReadOnly;
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}
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Api.JetAttachDatabase(this.Sesid, databaseName, grbit);
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try
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{
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Api.JetDetachDatabase(this.Sesid, databaseName);
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}
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catch (EsentDatabaseInUseException)
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{
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}
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return true;
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}
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catch (EsentFileNotFoundException)
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{
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return false;
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}
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catch (EsentDatabaseInvalidPathException)
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{
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return false;
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}
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catch (EsentErrorException)
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{
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return true;
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}
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}
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}
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/// <summary>
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/// Opens the database.
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/// </summary>
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/// <param name="databaseName">The file name (relative or absolute) at which the database will be opened</param>
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/// <returns>
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/// a Database object representing the database for this session
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/// </returns>
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/// <remarks>
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/// A database must first be attached (or created) before it can be
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/// opened successfully.
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/// </remarks>
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public IsamDatabase OpenDatabase(string databaseName)
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{
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lock (this)
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{
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this.CheckDisposed();
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return new IsamDatabase(this, databaseName);
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}
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}
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/// <summary>
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/// Opens the temporary database.
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/// </summary>
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/// <returns>
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/// A TemporaryDatabase object representing the temporary database for this session
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/// </returns>
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/// <remarks>
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/// Only one temporary database is supported per instance.
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/// </remarks>
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public TemporaryDatabase OpenTemporaryDatabase()
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{
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lock (this)
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{
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this.CheckDisposed();
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if (this.temporaryDatabase == null)
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{
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this.temporaryDatabase = new TemporaryDatabase(this);
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}
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return this.temporaryDatabase;
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}
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}
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/// <summary>
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/// Begins a new save point (level) for the current transaction on this
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/// session. Any changes made to the database for this save point
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/// (level) may later be kept or discarded by committing or aborting the
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/// save point (level).
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/// </summary>
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/// <remarks>
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/// Currently, there is a limit to how many save points (levels) are
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/// supported by the ISAM. Approximately seven save points (levels)
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/// are supported. Some ISAM functions also use some of these so the
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/// effective limit will vary with circumstance.
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/// </remarks>
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public void BeginTransaction()
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{
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lock (this)
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{
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this.CheckDisposed();
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Api.JetBeginTransaction(this.Sesid);
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this.transactionLevel++;
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}
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}
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/// <summary>
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/// Commits the current save point (level) of the current transaction
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/// on this session. All changes made to the database for this save
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/// point (level) will be kept.
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/// </summary>
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/// <remarks>
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/// <para>
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/// It is illegal to call this method when the session is not currently
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/// in a transaction. Use Session.TransactionLevel to determine the
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/// current transaction state of a session.
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/// </para>
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/// <para>
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/// Changes made to the database will become permanent if and only if
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/// those changes are committed to save point (level) zero.
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/// </para>
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/// <para>
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/// A commit to save point (level) zero is guaranteed to be persisted
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/// to the database upon completion of this method.
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/// </para>
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/// </remarks>
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public void CommitTransaction()
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{
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this.CommitTransaction(true);
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}
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/// <summary>
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/// Commits the current save point (level) of the current transaction
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/// on this session. All changes made to the database for this save
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/// point (level) will be kept.
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/// </summary>
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/// <param name="durableCommit">
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/// When true, a commit to save point (level) zero is guaranteed to be
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/// persisted to the database upon completion of this method.
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/// </param>
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/// <remarks>
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/// <para>
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/// It is illegal to call this method when the session is not currently
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/// in a transaction. Use Session.TransactionLevel to determine the
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/// current transaction state of a session.
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/// </para>
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/// <para>
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/// A commit to save point (level) zero is guaranteed to be persisted
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/// to the database upon completion of this method only if
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/// durableCommit is true. If durableCommit is false then the changes
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/// will only be persisted to the database if their transaction log
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/// entries happen to be written to disk before a crash or if the
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/// database is shut down cleanly.
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/// </para>
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/// </remarks>
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public void CommitTransaction(bool durableCommit)
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{
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lock (this)
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{
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||
|
|
this.CheckDisposed();
|
||
|
|
|
||
|
|
CommitTransactionGrbit grbit = CommitTransactionGrbit.None;
|
||
|
|
if (!durableCommit)
|
||
|
|
{
|
||
|
|
grbit |= CommitTransactionGrbit.LazyFlush;
|
||
|
|
}
|
||
|
|
|
||
|
|
Api.JetCommitTransaction(this.Sesid, grbit);
|
||
|
|
this.transactionLevelID[--this.transactionLevel]++;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/// <summary>
|
||
|
|
/// Aborts the current save point (level) of the current transaction on
|
||
|
|
/// this session. All changes made to the database for this save point
|
||
|
|
/// (level) will be discarded.
|
||
|
|
/// </summary>
|
||
|
|
/// <remarks>
|
||
|
|
/// It is illegal to call this method when the session is not currently
|
||
|
|
/// in a transaction. Use Session.TransactionLevel to determine the
|
||
|
|
/// current transaction state of a session.
|
||
|
|
/// </remarks>
|
||
|
|
public void RollbackTransaction()
|
||
|
|
{
|
||
|
|
lock (this)
|
||
|
|
{
|
||
|
|
this.CheckDisposed();
|
||
|
|
|
||
|
|
Api.JetRollback(this.Sesid, RollbackTransactionGrbit.None);
|
||
|
|
this.transactionLevelID[--this.transactionLevel]++;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/// <summary>
|
||
|
|
/// Aborts the current save point (level) of the current transaction on
|
||
|
|
/// this session. All changes made to the database for this save point
|
||
|
|
/// (level) will be discarded.
|
||
|
|
/// </summary>
|
||
|
|
/// <remarks>
|
||
|
|
/// It is illegal to call this method when the session is not currently
|
||
|
|
/// in a transaction. Use Session.TransactionLevel to determine the
|
||
|
|
/// current transaction state of a session.
|
||
|
|
/// <para>
|
||
|
|
/// Session.AbortTransaction is an alias for
|
||
|
|
/// <see cref="IsamSession.RollbackTransaction"/>.
|
||
|
|
/// </para>
|
||
|
|
/// </remarks>
|
||
|
|
public void AbortTransaction()
|
||
|
|
{
|
||
|
|
this.RollbackTransaction();
|
||
|
|
}
|
||
|
|
|
||
|
|
/// <summary>
|
||
|
|
/// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
|
||
|
|
/// </summary>
|
||
|
|
void IDisposable.Dispose()
|
||
|
|
{
|
||
|
|
this.Dispose();
|
||
|
|
}
|
||
|
|
|
||
|
|
/// <summary>Gets the Transaction ID at the specifed Transaction Level.
|
||
|
|
/// </summary>
|
||
|
|
/// <param name="level">The Transaction Level.</param>
|
||
|
|
/// <returns>The Transaction ID at the specifed Transaction Level.</returns>
|
||
|
|
internal long TransactionLevelID(long level)
|
||
|
|
{
|
||
|
|
return this.transactionLevelID[level - 1];
|
||
|
|
}
|
||
|
|
|
||
|
|
/// <summary>
|
||
|
|
/// Releases unmanaged and - optionally - managed resources.
|
||
|
|
/// </summary>
|
||
|
|
/// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
|
||
|
|
protected virtual void Dispose(bool disposing)
|
||
|
|
{
|
||
|
|
lock (this)
|
||
|
|
{
|
||
|
|
if (!this.Disposed)
|
||
|
|
{
|
||
|
|
if (this.cleanup)
|
||
|
|
{
|
||
|
|
if (this.temporaryDatabase != null)
|
||
|
|
{
|
||
|
|
this.temporaryDatabase.Dispose();
|
||
|
|
}
|
||
|
|
|
||
|
|
Api.JetEndSession(this.sesid, EndSessionGrbit.None);
|
||
|
|
this.cleanup = false;
|
||
|
|
}
|
||
|
|
|
||
|
|
this.Disposed = true;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/// <summary>
|
||
|
|
/// Checks whether this object is disposed.
|
||
|
|
/// </summary>
|
||
|
|
/// <exception cref="System.ObjectDisposedException">If the object has already been disposed.</exception>
|
||
|
|
private void CheckDisposed()
|
||
|
|
{
|
||
|
|
lock (this)
|
||
|
|
{
|
||
|
|
if (this.Disposed)
|
||
|
|
{
|
||
|
|
throw new ObjectDisposedException(this.GetType().Name);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|