datastore.cs

微软的行业应用解决方案示例

        /// </summary>
        /// <param name="connectionString">connection string</param>
        /// <returns>a specific implementation of a datastore</returns>
        public static DataStore GetDataStore(string connectionString)
        {
            return GetDataStore(_defaultProvider, connectionString, 
                                _defaultParameters);
        }


        /// <summary>
        /// This method creates a data store of the type passed into the 
        /// method. In creating the datastore it must construct it with a 
        /// connecion string and parameters.
        /// </summary>
        /// <param name="connectionString">connection string</param>
        /// <param name="implementationParameters">data store parameters</param>
        /// <returns>a specific implementation of a datastore</returns>
        public static DataStore GetDataStore(string connectionString,
                                             Parameters implementationParameters)
        {
            return GetDataStore(_defaultProvider, connectionString,
                                implementationParameters);
        }


        /// <summary>
        /// This method creates a data store of the type passed into the 
        /// method. In creating the datastore it must construct it with a 
        /// connecion string and parameters.
        /// </summary>
        /// <param name="providerType">type of provider</param>
        /// <param name="connectionString">connection string</param>
        /// <param name="implementationParameters">data store parameters</param>
        /// <returns>a specific implementation of a datastore</returns>
		public static DataStore GetDataStore(string providerType,
                                             string connectionString,
                                             Parameters implementationParameters)
		{
			Type dataStoreType = null;
			ConstructorInfo constructor = null;
			DataStore result = null;
			if (!_dataStores.ContainsKey(connectionString))
			{
				dataStoreType = Type.GetType(providerType, true, false);
				constructor = dataStoreType.GetConstructor(new Type[] { typeof(string), typeof(Parameters) });
				result = (DataStore)constructor.Invoke(new object[] { connectionString, implementationParameters });
				_dataStores.Add(connectionString, result);
			}
			else
			{
				result = _dataStores[connectionString];
			}
			return result;
		}


        /// <summary>
        /// Get a single value from the data store.
        /// </summary>
        /// <param name="selector">
        /// string to direct the method on what to retrieve
        /// </param>
        /// <returns>
        /// The first value that matches the selection criteria
        /// </returns>
        public abstract object GetValue(string selector);


        /// <summary>
        /// Get a single value from the data store.
        /// </summary>
        /// <param name="selector">
        /// string to direct the method on what to retrieve
        /// </param>
        /// <param name="parameters">
        /// collections of parameters for the selector
        /// </param>
        /// <returns>
        /// The first value that matches the selection criteria
        /// </returns>
        public abstract object GetValue(string selector,
                                        Parameters parameters);


        /// <summary>
        /// Method used to fire the trigger event.
        /// </summary>
        /// <param name="action">type of trigger</param>
        /// <param name="identifier">
        /// name of the table or view the action was performed upon
        /// </param>
        [SuppressMessage("Microsoft.Design",
                         "CA1031:DoNotCatchGeneralExceptionTypes",
                         Justification = "Allows all exceptions but system ones to be sent to the TriggerError event.")]
        protected void OnTrigger(TriggerType action, 
                                 string identifier)
        {
            TriggerEventArgs eventArg;
            EventHandler<TriggerEventArgs> currentSubscriber;

            // create event argument
            eventArg = new TriggerEventArgs(action, identifier);

            // trigger delegate
            if (Trigger != null)
            {
                foreach (Delegate currentHandler in Trigger.GetInvocationList())
                {
                    currentSubscriber = (EventHandler<TriggerEventArgs>)currentHandler;
                    try
                    {
                        currentSubscriber(this, eventArg);
                    }
                    catch (Exception ex)
                    {
                        OnTriggerError(currentSubscriber, ex);
                    }
                }
            }
        }


        /// <summary>
        /// Method used to fire the trigger event.
        /// </summary>
        /// <param name="source">Event handler </param>
        /// <param name="exception">
        /// name of the table or view the action was performed upon
        /// </param>
        [SuppressMessage("Microsoft.Design", 
                         "CA1031:DoNotCatchGeneralExceptionTypes",
                         Justification="Protects this method from having any exceptions thrown")]
        protected void OnTriggerError(EventHandler<TriggerEventArgs> source, 
                                      Exception exception)
        {
            TriggerErrorEventArgs eventArg;

            // create event argument
            eventArg = new TriggerErrorEventArgs(source, exception);

            // trigger delegate
            try
            {
                if (TriggerError != null)
                {
                    TriggerError(this, eventArg);
                }
            }
            catch
            {
                // ensure that this method does not throw an exception
            }
        }


        /// <summary>
        /// Get an enumerator to return a collection of named values.
        /// </summary>
        /// <param name="selector">
        /// string to direct the method on what to retrieve
        /// </param>
        /// <returns>enumerator of data in a row column heirarchy</returns>
        public abstract RowEnumerator Read(string selector);


        /// <summary>
        /// Get an enumerator to return a collection of named values.
        /// </summary>
        /// <param name="selector">
        /// string to direct the method on what to retrieve
        /// </param>
        /// <param name="parameters">
        /// collections of parameters for the selector
        /// </param>
        /// <returns>enumerator of data in a row column heirarchy</returns>
        public abstract RowEnumerator Read(string selector,
                                           Parameters parameters);


        /// <summary>
        /// Rollback changes since the start of a transaction.
        /// </summary>
        public abstract void Rollback();


        /// <summary>
        /// Method for insert, updating and deleting from a data store.
        /// </summary>
        /// <param name="update">
        /// string to direct the method on to update the date store.
        /// </param>
        public abstract void Save(string update);


        /// <summary>
        /// Method for insert, updating and deleting from a data store.
        /// </summary>
        /// <param name="update">
        /// string to direct the method on to update the date store.
        /// </param>
        /// <param name="parameters">
        /// collections of parameters for the selector
        /// </param>
        public abstract void Save(string update, Parameters parameters);
        #endregion


        #region Events
        /// <summary>
        /// Event for when data is changed. Subscribers are told what type of 
        /// change delete, insert, update and an identifier of what data was 
        /// changed.
        /// </summary>
        public event EventHandler<TriggerEventArgs> Trigger;
        /// <summary>
        /// Event for when a trigger event subscriber throws an exception.
        /// </summary>
        public event EventHandler<TriggerErrorEventArgs> TriggerError;
        #endregion

    }
}